EXECUTIVE SUMMARY

The Sustainable Water Well Initiative (SWWI) was created by Prairie Farm Rehabilitation Administration (PFRA) to extend the useful life of water wells by addressing concerns of declining well yield, water quality, and well lifespan. The goal of the SWWI is to provide improved advice on the diagnosis, prevention and rehabilitation of well problems. PFRA will also use the SWWI to facilitate technology transfer between government agencies, industry, and the public through Memoranda of Understanding with partners such as Droycon Bioconcepts Inc. (DBI) and Red Deer College.

As part of the SWWI, the role of microbiological activity in water well deterioration was investigated. The results of SWWI studies investigating the causes of declining well yield and water quality, led to the development of the Ultra Acid-Base (UAB^TM ) treatment process. This treatment process was designed to rehabilitate biofouled wells and was developed by DBI in conjunction with PFRA. In October 1997, PFRA and DBI field tested this water well treatment technology on one of the City of North Battleford's wells. Well 15 was chosen for the field test since the City of North Battleford had expressed interest in determining an effective rehabilitation method for this well. It also provided a unique opportunity to field test this treatment technique in a well field which had well-documented historical data and piezometers in place for monitoring.

As a first step, data available for Well 15 was collected and examined to provide a better understanding of the well and the surrounding aquifer. Secondly, the following diagnostic steps were performed before and after treatment of Well 15: a) collection of water chemistry data, b) surface and down hole camera inspection, c) pump testing and d) microbiological testing. The results of these diagnostic procedures were used to design the rehabilitation process and to provide feedback on the effectiveness of the rehabilitation.

Well 15 was installed in July 1989 and is located about 175 metres (575 ft) northeast of the North Saskatchewan River. The well has a double-walled gravel pack, with the screened well intake interval located between 18.3 m (60 feet) and 24.4 m (80 feet) below ground surface.

The City of North Battleford well field derives its water principally through induced infiltration from the North Saskatchewan River. The groundwater obtained from the aquifer is generally of good quality and is preferable to the City's surface water supply, since it only requires treatment for iron and manganese.

The City of North Battleford had indicated that Well 15 was not performing as efficiently as possible. The specific capacity of the well was used as a physical benchmark of the change in well production over time. An original specific capacity of 4.5 L/s/m (18 igpm/ft) was estimated for Well 15. However, the specific capacity of this well has been declining since it was placed into service in early 1990. Also, because of the limited amount of available drawdown in Well 15, the yield from the well has declined dramatically. Although there are no records of initial usage, it is believed that Well 15 was pumped at about 18.9 L/s (250 igpm) when the City of North Battleford originally placed it into production. However, just before the 1997 UAB^TM treatment, the City of North Battleford was operating Well 15 at a pumping rate of approximately 3.8 L/s (50 igpm) to maintain the pumping water level above the screen during prolonged periods of pumping. The reduction in the pumping rate indicates a production yield loss of about 80% from this well.

The City of North Battleford water utility began acid treatments on Well 15 to address the declining specific capacity and yield. This treatment was performed annually, beginning in 1993 and ending in 1996, but proved to be ineffective. After four yearly applications of the acid treatment, the specific capacity of Well 15 was only 18% of original after the 1996 treatment. The specific capacity declined further to 0.49 L/s/m (1.96 igpm/ft), or about 10% of original, by October 6, 1997.

The pre-treatment down hole video was taped by PFRA on July 30, 1997 and showed that the interior of the well screen was heavily biofouled by what appeared to be iron related bacteria (IRB). The slots of the screen were obscured by a thick, reddish-brown layer of biofilm. Visual inspection of the pump also showed the presence of iron-rich biofilms.

Post-treatment pump tests showed that the rehabilitation of Well 15 with the UAB^TM treatment technology is more effective than the previous treatments performed on the well. The post-treatment pump test performed on October 10, 1997 revealed that the specific capacity had recovered to 0.71 L/s/m (2.87 igpm/ft), a gain of 46% over the pre-treatment specific capacity. Further pump tests and well monitoring readings have been performed by the City of North Battleford since the 1997 UAB^TM treatment. They indicate that the specific capacity of Well 15 reached a high of 0.86 L/s/m (3.45 igpm/ft), approximately 76% higher than the pre-treatment specific capacity.

A methodical, long-range program of well inspection and monitoring should be established so that a regular program of preventative maintenance can guarantee the reliability of this source of water. Regular monitoring is a cost-effective way to maintain the economically efficient operation of the well, since it indicates the onset of problems such as biofouling. Maintenance, further sampling, or treatment can be recommended based on the review of the monitoring data.

Current well rehabilitation theory suggests that treatment or rehabilitation should take place as soon as there is a decrease in well performance. In any case, well rehabilitation procedures should be initiated before the specific capacity has declined 25 percent from the original specific capacity. Industry experience dictates that a well that has a specific capacity that is less than 75% of the original specific capacity often requires much larger expenditures for chemicals and labour without ever regaining the original performance. Often, it may be impossible to completely restore the original specific capacity of wells that are allowed to deteriorate further, even when using the best chemicals and rehabilitation techniques available.

CONCLUSIONS

1. The UAB^TM treatment process appears to be a viable treatment method for the City of North Battleford well field, since the 1997 treatment result for Well 15 is much better than any of the previous treatments applied to this well. The 1997 UAB^TM treatment increased the post-treatment specific capacity up to 176% of the pre-treatment specific capacity. The best conventional acid treatment only increased the post-treatment specific capacity to 118% of its pre-treatment specific capacity. With refinements to the treatment process, UAB^TM should prove to be even more effective in rehabilitating the City of North Battleford well field.
   
   
2. Well 15 is extremely biofouled and with a capacity reduction of 80% before the UAB^TM treatment, and therefore, it will probably never recover to its original specific capacity. Industry experience suggests that the maximum specific capacity that can be achievable for this well is about 2.3 L/s/m (9 igpm/ft), or 50% of the original specific capacity. This may be achieved with further UAB^TM treatment as proposed for 1998.
   
   
3. The total yearly energy savings from the 1997 UAB^TM well treatment of Well 15 is approximately $200, at a flow rate of 5.3 L/s (70 igpm). The increase in available water supply from Well 15 due to the 1997 UAB^TM treatment is about 129,166 m³/yr, an increase of 77% over the pre-treatment well yield. The City has the potential to save about $50,000 per year by treating this volume of groundwater instead of surface water. Potential cost savings based on estimates of the expected results from further treatment indicates that the City has the potential to save about $101,582 per year at Well 15.
   
   
4. Monitoring of the specific capacity in Well 15 revealed that the specific capacity peaked about one month after treatment. This lasted for about two months, at which time an apparent decline in specific capacity occurred. The latest data appears to show that the specific capacity has stabilized at about 0.8 L/s/m (3.2 igpm/ft). Further data needs to be collected to validate this trend.
   
   
5. Water chemistry and microbiological tests reveal that the 1997 UAB^TM treatment was effective in reducing both the bacterial aggressivity and iron concentrations in the water from Well 15. BART test results show that, as of February 2, 1998, the post-treatment bacterial aggressivity has been greatly reduced from the pre-treatment levels, with the IRB and SRB currently showing only mild aggressivity. In addition, the decrease in iron concentration is significant, although the post-treatment concentrations remain much higher than those in most of the other wells. The manganese concentration was not significantly affected and remains much higher than the values found in most of the other wells in the well field.

RECOMMENDATIONS

1. Monitoring and maintenance plans should be followed for the City of North Battleford well field to maintain the integrity of the infrastructure and to reduce long term capital outlay and operating costs. The City of North Battleford should measure static and pumping water levels in all wells on a monthly basis to determine changes in specific capacity. Routine BART tests should be conducted every three or four months to determine the aggressivity of the bacteria. Additional monitoring comprised of BART samples and pump tests should be conducted in Well 15 as soon as there is a noticeable reduction in specific capacity.
   
   
2. Well 15 must be shock chlorinated every six months using a 1000 mg/L chlorine solution made up of 40 litres of 12.5% liquid sodium hypochlorite.
   
   
3. It is recommended that any additional refinements of the UAB^TM treatment process address the possibility of further reduction of iron and manganese levels in Well 15.
   
   
4. Further rehabilitation of Well 15 is recommended. Additional treatment should substantially improve the specific capacity of the well and reduce the treatment requirements for the groundwater. The City should also realize a significant economic benefit from further treatment of this well.

BACKGROUND

INTRODUCTION

Water wells are the main water supply source for most rural residents on the Canadian Prairies and, as such, need to be managed in a sustainable and economically efficient manner. Until recently, little effort was applied to extending the life of water wells, and therefore, many water wells have experienced declining water quality or yield with time. Due to these problems, most of these wells are eventually abandoned, even though they may still be structurally sound. Consequently, a well owner can face substantial economic loss due to the replacement cost of a well.

The Sustainable Water Well Initiative (SWWI) was created by Prairie Farm Rehabilitation Administration (PFRA) to address concerns related to declining well yield, water quality, or well lifespan. The goal is to sustain the life of a water well by providing improved advice on the diagnosis, prevention and rehabilitation of well problems. PFRA will also use the SWWI to facilitate technology transfer between government agencies, industry and the public through Memoranda of Understanding with partners such as Droycon Bioconcepts Inc. (DBI) and Red Deer College.

As part of the SWWI, PFRA has directed studies that have investigated the causes of low-yielding wells and of water well deterioration. One such study, Microbiological Investigations of Water Wells in the Municipal District of Kneehill, Alberta (Cullimore and Legault, 1997) investigated the role of microbiological activity in water well deterioration. An extensive homeowner survey indicated that a majority of the reported problems are related to water quality. The most common water quality concerns expressed in the survey were taste, odour, mineralization and the presence of brown or black slimes. It was concluded that these observations are consistent with biofouling caused by naturally occurring nuisance bacteria present in the water well environment. As a result of this microbiological study, a method for treating biofouled wells was developed by DBI in conjunction with PFRA and is referred to as the Ultra Acid-Base (UAB^TM ) treatment process. A detailed description of this treatment process and the treatment equipment is provided in Development of Ultra Acid-Base (UAB^TM ) Water Well Treatment Technology (PFRA and DBI, 1997).

In July and August 1997, PFRA undertook a joint venture with DBI to field test the UAB^TM treatment technology. Representatives from the City of North Battleford had previously approached Dr. Cullimore of Droycon Bioconcepts Inc. with concerns about the steady decline in water production from their well field. Upon review of the City's well field history, it was decided that Well 15 would provide a good site to field test the UAB^TM treatment process. PFRA assisted with the field trials as per the joint venture agreement with DBI. This report summarizes the details of the 1997 UAB^TM water well treatment technology field test on Well 15. The microbiological aspect and UAB^TM procedure summary contained in this report have been summarized from the report entitled Implementation of the UAB^TM (Ultra Acid Base) Process to Rehabilitate Biofouled Water Well #15 for the City of North Battleford, Saskatchewan (a pilot project) (Keevill, 1998).

1.2 WELL 15 DATA

1.2.1 Construction Details

Well 15 was installed in July 1989 and is located about 175 metres (575 ft) northeast of the North Saskatchewan River (see Figure 1). A 17.8 cm (7 inch) diameter observation well and four 5 cm (2 inch) diameter piezometers (1-89, 2-89, 3-89, and 5-89) are in close proximity to the pumping well.

Well 15 was completed with 18.3 metres (60 feet) of 12-inch diameter inner steel casing below ground surface, 6.1 m (20 feet) of 80 slot (0.080 inch spacing) Johnson stainless steel wire-wrap screen and a 0.6 m (2 foot) stainless steel sump. The original bore hole was 0.9 m (3 feet) in diameter and allowed the placement of a double gravel pack envelope around the well screen with each pack about 15 cm (6 inches) in thickness. The inner pack consists of 3 to 6 mm (1/8 to 1/4 inch) filter gravel material and the outer pack consists of 0.8 mm (1/32 inch) filter sand material. Figure 2 provides the relevant well construction details.

1.2.2 Geochemistry and Site Hydrogeology

The groundwater obtained from the aquifer is generally of good quality and is preferable to the City's surface water supply as it only requires treatment for iron and manganese. Iron and manganese constituents are present in concentrations exceeding the municipal aesthetic objectives of 0.3 mg/L and 0.05 mg/L, respectively. Table 1 provides the results of the limited water chemistry analyses performed by DBI staff on samples collected on December 16, 1997. The Well 15 data reflects the groundwater chemistry after the UAB^TM treatment. Also, the high turbidity values may be caused by post-sampling biological activity in the non-preserved samples.

TABLE 1

North Battleford Well Field Water Chemistry (December 16, 1997)

Well Number	Iron (mg/L)	Manganese (mg/L)	Electrical Conductivity (mhos/cm)	Lab pH	Salinity (%)	Turbidity (NTU)
9	1.23	0.76	730	8.30	0	36
11	0.5	0.23	295	8.17	0	22
12	0.92	0.4	305	8.13	0	23
13	1.32	0.48	320	8.11	0	23
14	1.11	0.42	350	8.11	0	21
15	1.56	0.68	440	8.25	0	22

The City of North Battleford well field, including Well 15, derives its water principally through induced infiltration from the North Saskatchewan River. The aquifer, in which the wells have been completed, is a river terrace deposit that consists primarily of unconsolidated fine sand and silt-sized material.

1.2.3 Past Performance

The original specific capacity of Well 15 is used as the benchmark for the change in well production with respect to time. However, the original specific capacity is only an estimate, since the original pump test records for this well are incomplete. The original pump test data did not provide the drawdown at specific time intervals and did not indicate the total duration of the test. The original pump test data indicated a static water level of 4.55 m (14.92 feet), an end of test pumping level of 10.62 m (34.83 feet) and a pumping rate of 27.2 L/s (359 igpm), as shown in Appendix A. With these values, and assuming a standard two hour pump test was conducted, an original specific capacity of 4.5 L/s/m (18 igpm/ft) has been estimated for Well 15. Also, no data was collected from the observation wells during the original pump test, precluding the calculation of the well efficiency.

The specific capacity of this well has been declining since it was placed into service in early 1990. Prior to the UAB^TM treatment, a pump test performed on October 6, 1997 indicated that the specific capacity had declined to 0.49 L/s/m (1.96 igpm/ft), or about 10% of the original specific capacity.

The yield from Well 15 has also declined dramatically since the well has a limited amount of available drawdown. Although there are no records of original usage, it is believed that the original well production rate was about 18.9 L/s (250 igpm). However, just before the 1997 UAB^TM treatment, the City of North Battleford was operating Well 15 at a pumping rate of approximately 3.8 L/s (50 igpm) to maintain the pumping water level above the screen during prolonged periods of pumping. This equates to a production yield loss of about 80% from this well.

1.2.4 Past Rehabilitation Efforts

The City of North Battleford water utility began acid treatments on Well 15 to address the declining specific capacity and yield. This treatment was performed annually, beginning in 1993 and ending in 1996. The acid treatment involved pouring 800 litres (176 imp.gal) of hydrochloric acid (33% solution) into the well and air surging the water in the well column.

The acid treatment technique used on Well 15 proved to be ineffective. Prior to the first treatment in 1993, the specific capacity had declined to 3.8 L/s/m (15.1 igpm/ft), or 77% of original. The 1993 acid treatment resulted in a specific capacity recovery of only 0.2 L/s/m (0.8 igpm/ft), a 5% increase. After four yearly applications of the acid treatment, the specific capacity of Well 15 was only 18% of original after the 1996 treatment. The specific capacity declined further to 0.49 L/s/m (1.96 igpm/ft), or 10% of original, according to a pump test performed on October 6, 1997. The historical well rehabilitation results for Well 15 are shown in Figure 3.

1.3 WATER WELL MICROBIOLOGY

1.3.1 Well Biofouling and Plugging

Over time, water wells can become biofouled and eventually the well and aquifer surrounding the well intake will become plugged. Biofouling refers to the condition where a well has a significant number of bacteria growing around its intake, but the inflow of water has not been noticeably affected. Once the bacteria have had an adverse impact on the well's performance, the well is said to be plugging or plugged, depending on the degree to which the performance is affected.

The creation of biofilms are generally the cause of declining well yield (plugging) when microbiological organisms are present in the groundwater surrounding the well. Biofilm (or slime) is formed when bacteria extrude polymeric substances for protection. Some of the byproducts associated with bacterial growth, such as iron and manganese salts, become accumulated on or in these mucilaginous/gel-like secretions. These biofilms can also contain trapped silt and clay size particles. They will coat, eventually harden, and plug the well screen, the sand pack, the surrounding aquifer material and even water lines. This can lead to problems such as reduced well yield, restricted flow in the water distribution system, staining of plumbing fixtures and laundry, increased iron concentrations, increased turbidity and even increased corrosion of metal.

Two of the main bacteria types that cause problems in water wells are iron related bacteria (IRB) and sulphate reducing bacteria (SRB). These bacteria are not considered a health hazard, but can be quite a nuisance to well owners. A brief description of these bacteria are provided in the following sections.

1.3.2 Iron Related Bacteria

Iron related bacteria (IRB) are a common nuisance in water wells because they favour the environment that these wells provide. Although IRB are generally considered as aerobic organisms requiring oxygen to survive, they have been found to grow in waters with very low oxygen content. These bacteria thrive in water which contains 0.5 to 4 mg/L of dissolved oxygen and will grow in water having iron concentrations as low as 0.01 mg/L. Some IRB are considered autotrophic (self-sufficient) organisms because of their limited ability to use dissolved iron/manganese in water as an energy source. They also prefer a temperature range of 5°C to 15°C, but are known to grow at temperatures ranging from 0°C to 40 °C. The optimum pH for their survival is around 6.5 pH units, but growth will occur in the range of 5.5 to 8.8 pH units. IRB are not affected by light intensity and will grow in complete darkness or in areas fully exposed to light. The optimum ranges for the growth factors mentioned above are typical of the water well environment. In most cases, the limiting factor to growth for these bacteria is phosphorus.

There are a number of visual indications of an IRB problem. These indications include: i) discoloured water (red, yellow, or orange), ii) slime/biofilm (red, brown, black) on the casing, pump, or well screen, iii) a smell resembling fuel oil, cucumber, or sewage, or iv) a sheen on the water surface that breaks up when disturbed (unlike a petroleum sheen). As the number of bacteria increases, the water may become more turbid, may turn reddish in colour, and may gain an unpleasant, sometimes metallic, taste. The deposition of iron and manganese salts in IRB biofilms results in its characteristic reddish-brown to black colour.

IRB are a diverse group and are difficult to enumerate. These bacteria function under different reduction-oxidation (redox) conditions and utilize a variety of substrates for growth. By routine (e.g. monthly) testing of a water or wastewater using the Biological Activity Reaction Test (BART) technique, the levels of aggressivity, possible population, and community structure of an IRB population can be determined.

1.3.3 Sulphate Reducing Bacteria

Sulphate reducing bacteria (SRB) are more often found in systems with concurrent fouling problems. The two most common species of these bacteria are Desulfovibrio desulfuricans and Desulfotomaculum nigrificans. These organisms favour an anaerobic (oxygen free) environment. However, this does not mean that they will not grow in oxygen-rich environments. In fact, SRB can thrive under slimy deposits even though aerobic conditions exist in the main body of water. For instance, SRB will establish themselves in a water well environment by locating under layers of aerobic bacteria such as IRB. If there is a layer of IRB biofilm on a casing, the IRB will use up all of the oxygen and the SRB will thrive in the anaerobic zone between the IRB and the casing surface.

Visual indications of SRB include a reddish or yellowish nodule on metal surfaces that exhibits black corrosion by-products when broken open. When the complete nodule is removed, a bright metallic pit is often seen and severe localized pitting is evident. If hydrochloric acid is added to the black deposit, hydrogen sulfide will be released with its characteristic rotten egg odour.

SRB obtain their energy from the anaerobic reduction of sulfates. Even small amounts of oils and grease will provide nutrients for SRB growth. Stagnant water and low flow conditions will also increase the chance of growth. This bacteria type is also an agent of corrosion because it produces an enzyme, hydrogenase, that enables it to use elemental hydrogen generated at the cathodic site to reduce sulfate to hydrogen sulfide. It therefore acts as a cathodic depolarizing agent. The electrolytic corrosion of iron by this process is very rapid and unlike ordinary rusting, is not self-limiting.

1.4 UAB^TM TREATMENT THEORY

The UAB^TM treatment process involves three phases of chemical application to remove the plugging biofilms. The chemical applications are used in conjunction with heat to facilitate the removal of the biomass. The first phase is intended to shock the bacterial cells in the biofilms, the second to disrupt (break up) the biofilms, and the third to disperse the biofilms and other plugging material. Lab studies conducted by Keevill and Legault of DBI to develop and test the UAB^TM treatment process have shown that each phase of the process is necessary to effectively penetrate and remove the biofilm material. In addition, sufficient volumes of the hot water solutions must be added at each stage to increase the activity of acid, base and surfactant, and to reach areas of biofouling adjacent to the well and extending into the aquifer. A summary of these lab studies was published in April, 1997 (Keevill, 1997). The phases are discussed in further detail in the following sections.

The described procedure does not completely eliminate iron bacteria or other types of bacteria from the water system, but will hold them in check. To ensure that the bacteria do not re-establish themselves, a regular maintenance program must be implemented. If the well is severely biofouled and plugged, it may require two or three treatments before a significant improvement is noticed.

1.4.1 Shock Phase

The purpose of the shock phase is to: (1) kill bacterial cells suspended in the water, (2) stress the biofilms, which causes top layers to shear off and lower layers to compress, (3) increase bacteria metabolic rates at the fringe of the heat zone to increase the rate at which cells absorb the disinfectant, and (4) soften encrustations or hardened bacterial plugs (Smith, 1995).

The shock phase of UAB^TM treatment process begins after pre-heating the well intake area with hot water to increase the down hole temperature to about 65°C. The shock phase itself involves application of a hot water solution, disinfectant, and wetting agent (surfactant). The water in the well and surrounding aquifer is maintained at a temperature of at least 65°C, since these relatively high temperatures are lethal to some of the bacteria. In addition, high temperatures increase the rate at which chemicals react and reduce the amount of disinfectant needed to kill bacterial cells. The wetting agent helps the hot water and disinfectant to penetrate the biofilms.

1.4.2 Disrupt Phase

The purpose of the disrupt phase is to kill the bacteria by causing a shift from a strongly acidic to a strongly alkaline solution. Although some bacteria thrive in acid conditions and some in alkaline conditions, a shift of 7 pH units over a short period of time is generally lethal to most bacteria found in groundwater. The target pH shift generally involves a pH drop to 3 followed by an increase to 10.

The first stage of this phase is to add a hot water and acid solution to the well until the pH in the well intake area reaches about 3. If possible, the acid solution should be left in the well overnight before the next stage of the process is initiated, since the acid also helps to dissolve iron and manganese oxides which collect in the biofilms and encrustations.

The second stage requires the addition of an alkali and wetting agent solution at a pH of about 10. The wetting agent is added during the alkaline stage to help break up the biofilms and keep other plugging materials in suspension (e.g. silts and clays), so that they can be more easily removed during the disperse phase (Cullimore, 1993 and Smith, 1995).

1.4.3 Disperse Phase

This phase is designed to disperse or remove the biofilms and other plugging material from the aquifer by surging, bailing and pumping the well. The purpose of surging the well is to further suspend plugging material so it can be removed by bailing and pumping. Heavy debris which falls to the bottom of the well during treatment can plug the intake area of a pump and adversely affect cleaning of the well screen. Therefore, this material is removed by bailing the well. Finally, the treated water is pumped from the well. Pumping should continue until the water is clear and the pH is neutral.

2.0 DIAGNOSTIC PROCEDURES AND RESULTS

There are a number of steps required to diagnose the cause of decreasing well production. This data collection is an important step, both for the determination of the problem and for the design of the rehabilitation process. Data regarding the past performance of the well, the physical structure of the well, the operating procedures and the chemistry of the groundwater are all important factors that must be taken into account. Some of this data can be retrieved from the well drilling record. This record should include: original well production rate, well location, well intake length and diameter, total well depth and well construction materials. If the well drilling record is not available, this information must be obtained from the well owner or by some other method (e.g. down hole video camera, sounder, gamma logs, etc.). Other data must be obtained from the owner and possibly by collecting samples prior to the rehabilitation.

The data collected from the City of North Battleford with regard to Well 15 was examined and in some cases was consolidated to provide a better understanding of the well and well field. Appendix A contains pertinent data for this well and includes a copy of the original well record, a diagram of the well construction details, pre- and post-rehabilitation pump test data and chemistry data.

The following diagnostic steps were performed before and after treatment of Well 15: i) collection of water chemistry data, ii) surface and down hole camera inspection, iii) pump testing and iv) microbiological testing. The results of these diagnostic procedures assisted in the design the 1997 rehabilitation process. These procedures were also used to provide feedback on the effectiveness of the rehabilitation. Results are provided in the following sections.

2.1 WATER CHEMISTRY DATA

Pre- and post-treatment water samples were collected to determine changes in water chemistry. The September 15, 1997 water chemistry sample was collected from Well 15 and analysed by the Saskatchewan Research Council (SRC) Analytical Division in Saskatoon. The October 10, 1997 sample and the December 12, 1997 sample were analysed by DBI staff.

Table 2 reveals that the 1997 treatment effected a change in concentrations of some of the chemical constituents in the water. However, further sampling may be required to substantiate the stability of these values over time. The iron concentration shows the most significant decrease, which will reduce the amount of water treatment required for this water source. However, the iron concentration in Well 15 is still significantly higher than the concentrations in the majority of the other wells (see Table 1). The manganese concentration was not significantly affected and remains much higher than the values found in most of the other wells in the well field.

The results of an analysis performed on the purge water have been included as a point of interest and comparison. The data presented in Table 2 indicates a high iron concentration in the purge water sample. This shows that the treatment technology was effective in dissolving iron down the well. However, we cannot be sure of the source of the iron in this case. It is likely that much of the iron was dissolved from the iron rich biofilms that were plugging the well, but some of the iron must also be attributable to the acidization of the well casing and the drilling tools used to surge the well. Also, the low manganese concentrations in the purge water, relative to the pre- and post-treatment water samples, may indicate that the manganese deposits in the biofilm were not readily removed during the treatment.

TABLE 2

Well 15 Water Chemistry Analyses

Sample Date	Sample Description	Sample Colour	Iron (mg/L)	Manganese (mg/L)	Electrical Conductivity (mhos/cm)	Lab pH	Salinity (%)	Turbidity (NTU)
Sept.15,1997	Clean Water	Colourless	2.3	0.76	619	7.56	0	N/A
Dec.16, 1997	Clean Water	Colourless	1.56	0.68	440	8.25	0	22
Oct.10, 1997	Purge Water	Black	28.9	0.09	28,500	11.9	18.3	N/A

2.2 SURFACE AND DOWN HOLE CAMERA INSPECTION

One of the initial and potentially most revealing diagnostic procedures is to simply inspect the discharge line and the pump. With a little experience, this visual inspection can indicate if a biofouling problem is present. A down hole video camera is then used to provide a visual record of the interior well condition before treatment. The physical condition of the well casing and well intake area, as well as the degree of bacterial/biofilm growth, is observed to aid in the design of the treatment program. The pre- and post-treatment videos are also compared to provide some qualitative measure of the effectiveness of the treatment within the well.

The pre-treatment down hole video was taped by PFRA on July 30, 1997 and revealed that the interior of the well screen was heavily biofouled with what appeared to be iron-related bacteria (IRB). The slots of the screen were obscured by a thick, reddish-brown layer of biofilm. Visual inspection of the pump (Photo 1), after it was removed from the well prior to UAB^TM treatment, also showed the presence of iron-rich biofilm. Inspection of the drop pipe in the well that connects the pump to the collection system also revealed the presence of corrosion at the joints. This corrosion was likely microbially induced by sulphate reducing bacteria which can create sulphuric acid in concentrated areas, which in turn initiates corrosion.  The SRB live in anaerobic conditions beneath the protective mass of biofilm formed by iron related bacteria.

2.3 PUMP TEST

A two hour pump test at 5.3 L/s (70 igpm) was performed before and after well treatment to evaluate the effectiveness of the treatment. During each test, water was pumped from the well at a constant rate and the water level was recorded at regular time intervals to provide drawdown curves (see Figure 4) and to determine the well's specific capacity. The specific capacity results for the well, before, during and after treatment, were compared to provide a quantitative measure of the effectiveness of the treatment.

The pre-treatment pump test was performed on October 6, 1997 at 5.3 L/s (70 igpm) with a 15 cm (6 inch) pump supplied by PFRA. The resulting specific capacity after two hours of pumping was 0.49 L/s/m (1.96 igpm/ft).

The post-treatment pump test was performed on October 10, 1997, after the second surging interval and subsequent well clean out. Results of that pump test revealed that the specific capacity had recovered to 0.72 L/s/m (2.87 igpm/ft), a gain of 46% over the pre-treatment specific capacity. Further pump tests and well monitoring readings have been performed by the City of North Battleford since the 1997 UAB^TM treatment. They indicate that the specific capacity of Well 15 reached a high of 0.86 L/s/m (3.45 igpm/ft), 76% higher than the pre-treatment specific capacity. The readings are included in Appendix B.

The UAB^TM treatment process appears to be a viable treatment method for the City of North Battleford well field since the 1997 treatment result for Well 15 is much better than any of the previous treatments. Figure 5 shows the relative effectiveness of the UAB^TM treatment by comparing the highest post-treatment specific capacity to the historical well rehabilitation record that was presented in Figure 3. With refinements to the treatment process, UAB^TM is expected to be even more effective in rehabilitating the City of North Battleford well field.

Unfortunately, Well 15 will probably never recover to its original specific capacity, since biofouling of the well is so severe that the well has lost about 90% of its production capacity. It is suggested that the maximum specific capacity that could be achieved for this well is about 2.2 L/s/m (9 igpm/ft), or 50% of the original specific capacity. This specific capacity may be achieved with further UAB^TM treatment as proposed for 1998.

The hypothesis that the full effect of the UAB^TM treatment would not be seen for a number of weeks was substantiated. From the data collected by the City of North Battleford following the 1997 UAB^TM treatment, a gradual increase in the specific capacity of Well 15 was observed until approximately three months after treatment, when the maximum specific capacity of 0.86 L/s/m (3.45 igpm/ft) was reached. Figure 6 shows the change in specific capacity following the treatment.

Figure 6 also shows that the specific capacity of Well 15 appears to be declining. This is likely caused by the quick regrowth of the bacteria and biomass that could not be removed from the aquifer surrounding the well. The City conducted a maintenance treatment on the well (shock chlorination per DBI instructions) on February 10, 1998. However, this treatment did not alter the specific capacity significantly, as indicated in Appendix B.

2.4 MICROBIOLOGICAL TESTING

The majority of the following data has been summarized from the report entitled Implementation of the UAB^TM (Ultra Acid Base) Process to Rehabilitate Biofouled WaterWell 15 for the City of North Battleford, Saskatchewan (a pilot project), February 1998 (Keevill 1998). Please refer to the original report for more detail.

Water samples were taken during the pre- and post-treatment pump tests to determine the degree of microbiological activity. Water samples were collected at set time intervals during the pump tests (5, 10, 20, 30, 60, 120 minutes). The analyses for bacterial activity were conducted with the use of Biological Activity Reaction Tests (BART^TM) which determine the presence and aggressivity of the nuisance bacteria causing the biofouling problems. The BARTs used for North Battleford were the IRB-BART (for iron related bacteria), the SRB-BART (for sulphate reducing bacteria), the TAB-BART (for total aerobic bacteria), the DN-BART (for denitrifying bacteria) and the TCOLI-BART (for total coliform bacteria).

There have been four sets of microbiological samples collected from Well 15. The initial set of microbiological samples were collected during a PFRA visit to the well field on July 30, 1997. These samples were analysed for TAB, IRB and SRB, and the results were used to design the treatment process for Well 15. The three remaining sets of samples were collected on October 6, 1997 (pre-treatment), October 10, 1997 (post-treatment) and February 2, 1998. These samples were tested for TAB, IRB, SRB, DN and TCOLI. Well 15 was shut down for 24 hours prior to pump/BART testing as per Droycon's sampling protocol. A laser particle counter was also used to determine the average particle sizes in some of the samples.

The graphical results of the BART sampling are presented in Appendix C. Table 3 presents the interpreted aggressivity of the different bacteria types tested for in Well 15.

TABLE 3

Well 15 Bart Test Interpretation Results

BARTTM Test	BARTTM Interpretation Results By Date
	July 30, 1997	October 6, 1997	October 10, 1997	February 2, 1998
TAB	aggressive	aggressive	moderately aggressive	aggressive
IRB	aggressive	very aggressive	aggressive	mildly aggressive
SRB	aggressive	moderately aggressive	aggressive	mildly aggressive
DN	-	gassing at day 2 (pos)	gassing at day 3 (neg)	various gassing (neg)
TCOLI	-	negative	negative	negative

The results show that, as of February 2, 1998, the post-treatment bacterial aggressivity has been greatly reduced from the pre-treatment levels, with the IRB and SRB currently showing only mild aggressivity.

In the case of the City of North Battleford well field, there may be up to three zones of activity between the river and the well which influence the microbiology of the site. There is likely an oxidative zone next to and below the river because of the infiltration of oxygenated water to the underlying aquifer. There is also a reductive zone between the well and the river and an oxidative zone next to the well. Biofouling by IRB is expected to be more laterally extensive than in typical aquifers that are not influenced by surface water bodies, since extensive oxygenated zones are expected to be present in the aquifer.

Laser particle counting performed on samples taken before and after treatment have revealed a decrease in the average size of particles entering the well. Four months after treatment, the average particle size shrank from a pre-treatment size of 1.93 micrometres (m) to 1.44 m , a 25% reduction.

3.0 UABTM TREATMENT OF WELL 15

This section summarizes the UAB^TM treatment procedure used to rehabilitate Well 15. Treatment began on October 6, 1997 and was completed on October 9, 1997. The total volume of chemicals and hot water used is provided in Table 4. The individual treatment steps are summarized below.

TABLE 4

Volume of Chemicals Used for Well 15 UAB^TM Treatment

Chemical	Volume (litres)
Chlorine (12.5% sodium hypochlorite)	25
Arccsperse CB-4 Wetting Agent	200
Hydrochloric Acid (31.4%)	680
Caustic Soda (50%)	225
Hot Water (80oC - 85oC)	25,000
TOTAL	26,130

3.1 PRE-TREATMENT

Injection of 1500 litres (400 imp.gal.) of an 80°C water and acid solution was performed to increase the down hole temperature to 60°C. The pH of this solution was 2.5 pH units. A 20 minute holding period was allowed so that the heat in the water could move into the formation and elevate the temperature in the porous media, thereby allowing the chemicals added during later steps to act more effectively.

3.2 INITIAL WELL CLEANING

After pre-treatment, the well was surge blocked and brushed for one hour at 0.6 to 0.9 m/s (2 to 3 ft/s), starting at the top of the screen and gradually working down. Sediment that collected in the bottom of the sump was initially cleaned out with a mechanical bailer, but this method was abandoned when it proved ineffective. Subsequently, an air lift pumping system supplied by the City of North Battleford was used to clean the sediment from the sump. The well was allowed to sit overnight to allow the heat and acid added during the pre-treatment phase to continue to work.

3.3 DISINFECTION AND WETTING AGENT

This next step was designed to stress the biofilm by introducing 5000 litres (1100 imp.gal.) of chlorine (sodium hypochlorite) and wetting agent (CB-4) solution into the well. Fifty litres (11 imp.gal.) of each chemical were used to obtain a 1% concentration by volume. This solution was heated to approximately 84°C to increase bacteria metabolic rates, and therefore, increase bacteria uptake of the chemicals. A holding period was applied to allow the heat and chemicals sufficient time to penetrate the biofilm. The volume of the biofilm was expected to have decreased at the end of this phase due to the chemical stress applied.

3.4 ACID DISRUPTION

During this phase, a solution of hot water, acid and wetting agent was discharged down hole at a pH of 2.5 to 3.0 pH units. The total volume of solution added at this step was 5600 litres (1200 imp.gal.), which included 600 litres of concentrated hydrochloric acid and 56 litres of wetting agent. Assuming radial influence of the treatment solution around the well screen, it is estimated that the treatment zone extended for 2 metres (6.5 ft) around the well. An overnight holding period allowed time for the various treatment zones within the aquifer to react with one another, before proceeding to the alkali disruption stage.

3.5 ALKALI DISRUPTION

In this step, an increase in the disruption of the biofilm was achieved by alkalization. Caustic soda is the primary agent for the pH shift from the acid range to the base target of 10.5 to 12 pH units, but the use of Arccsperse CB-4 also helps to increase the pH. This pH shift was achieved by using 5200 litres (1200 imp. gal.) of hot solution, of which 200 litres was concentrated caustic soda and 52 litres was CB-4. Assuming radial influence of the treatment solution, it was estimated that the zone of impact extended for about for 3 metres (10 feet) from the well. At this point, there was a reactive front within the aquifer at the interface between the alkali and acid solutions. An overnight holding period maximized the effects of the disruption on the plugging biofilms.

3.6 DISPERSION/REDEVELOPMENT

The dispersion or redevelopment phase of the UAB^TM treatment was completed by mechanical surging with a surge block attached to the tools of a cable tool rig. The drilling motion of the tools causes the water level to rise and fall within the well, which in turn forces water to flow into and out of the screen and aquifer. After initial redevelopment of Well 15 with two hours of surging, the well sump was pumped clean by air lifting. A 6-inch diameter submersible pump was placed in the well, with the pump intake set above the well screen. To clear the purge water from the well, the pump was initially operated at 6.8 L/s (90 igpm) and gradually increased to 9.5 L/s (125 igpm) over the two hour pump out period. The water was very turbid and black for the first 15 minutes of pumping and gradually cleared. After beginning the two hour pump test, it was determined that the specific capacity had not changed significantly from the pre-treatment level and it was decided that a second two hour surging interval was required. A second clean out period and subsequent pump test were then performed, with the results of the second pump test showing a significant improvement in the specific capacity of the well.

4.0 ECONOMIC CONSIDERATIONS FOR WELL REHABILITATION

There are several ways that cost savings from well rehabilitation can be calculated. One method is to calculate the cost savings associated with reduced power requirements corresponding to a decreased water level drawdown within the well for a given pumping rate. Another method of determining the economics of the well rehabilitation is to calculate the benefit of the increase in available water supply from the well. Calculations for both of these methods are outlined in Appendix D of this report, with the findings discussed in the following sections. The important qualifying assumptions in Appendix D must be considered to obtain a complete understanding of the economics results.

4.1 ENERGY SAVINGS DUE TO DECREASED DRAWDOWN

The energy that a pump motor has to provide to a submersible pump decreases in proportion with decreasing water level drawdowns. The electrical energy used by an electric motor coupled to a pump can be calculated given the pump discharge, the drawdown, the static water level and the pump and motor efficiency (Helweg, 1982). The total cost of the energy is the unit energy cost multiplied by the units of energy used. The energy savings at a given flow rate is therefore calculated by subtracting the post-rehabilitation energy costs from the pre-rehabilitation energy costs at that flow rate.

Cost of pumping Well 15:

• at 70 igpm before 1997 rehabilitation = $0.170/h = $1489/yr
• at 70 igpm after 1997 rehabilitation = $0.147/h = $1288/yr

The total yearly energy savings from the 1997 UAB^TM well treatment of Well 15 is approximately $200, at a flow rate of 70 igpm. The energy savings alone therefore do not provide economic justification for well rehabilitation for this well field, since the amount of available drawdown in the well field is very small. In effect, well rehabilitation in this well field cannot possibly cause the large changes in drawdown that would be necessary to provide substantial energy cost savings at the City's current electrical rate.

4.2 COST SAVINGS FROM
AN INCREASE IN GROUNDWATER SUPPLY

The benefit derived from the increased availability of groundwater can be approximated by using the alternative cost method, which determines the cost of obtaining water from the next best source (Helweg, 1982). Therefore, the benefit of obtaining water from a given source is approximated by subtracting the cost of obtaining water from that source from the cost of obtaining water from the next best source. In this case, the assumption is that the extra water supply from Well 15 is required, and if not obtained from Well 15, would have to be supplied from the North Saskatchewan River. The cost savings to the City of North Battleford can therefore be determined by calculating the extra volume of groundwater that is now available from Well 15 and multiply the cost differential of treating surface water versus treating groundwater.

Groundwater available from Well 15 before UAB^TM treatment = 167,513 m³/yr

Groundwater available from Well 15 after UAB^TM treatment = 296,679 m³/yr

The increase in available water supply due to 1997 UAB^TM treatment is therefore 129,166 m³/yr, an increase of 77% over the pre-treatment well yield. The City pays approximately $0.387/m³ more to treat surface water than groundwater (1996 data from Ivan Katzell, City of North Battleford Plants Foreman). The annual cost savings of treating 129,166 m³ groundwater rather than the same volume of surface water is therefore approximately $50,000 from the 1997 UAB^TM treatment of Well 15.

4.3 POTENTIAL BENEFIT OF FUTURE WELL REHABILITATION

If Well 15 were to undergo further rehabilitation to the extent that a well yield of 180 igpm (50% of the original 1990 well yield of 359 igpm) was made available, this well could possibly sustain a pumping rate of 110 igpm over and above the 1997 pre-treatment well yield. This converts to 262,485 m³/yr, assuming that the pump will be running constantly. If all of this additional water were used to replace the same volume of surface water, the cost savings to the city could be approximately $101,582/yr (volume x $0.387/m³ cost difference between treating surface water and groundwater).

5.0 DISCUSSION OF WELL MAINTENANCE

Systematic well rehabilitation using proper methods and materials can usually restore or even increase the specific capacity of the well above the original and can maintain this specific capacity for a significant length of time. A methodical, long-range program of well inspection and monitoring is required to identify problems so that a regular program of preventative maintenance can guarantee a reliable source of water.

5.1 MONITORING PROCEDURES

Regular monitoring is a cost-effective way of maintaining peak operation of the well since it indicates the onset of problems such as biofouling. Without monitoring, biofouling may progress unnoticed until plugging of the well intake occurs and the pump breaks suction. By this point, the biofilm has become so well established that excessive time and materials have to be used to overcome the mature biofilm plug. In fact, with a mature biofilm, the well may never be restored to its original specific capacity, no matter how much time and money is spent on the rehabilitation process.

A monitoring program can be set up to take frequent readings and water samples at the beginning, perhaps at the rate of one per month or more. However, once the program has been well established and the data reviewer has become familiar with the operational characteristics of the well, readings and sampling intervals can be modified to periods that are designed to minimize costs but still observe all potential events.

One essential reading is the drawdown at a given pumping rate, which will allow calculation of the specific capacity of the well. When specific capacity is plotted against time, the resulting graph provides a quick indication of the condition of the well intake area. Maintenance, further sampling, or treatment can then be recommended based on the reviewer's experience with that well.

Microbiological sampling on a regular basis will indicate the aggressivity of the bacteria. The level of aggressivity will dictate the action to take, as outlined in the draft report entitled Biological Testing in Support of the Water Well Rehabilitation Initiative (DBI, 1998). The report states that: "high aggressivity requires treatment as early as is convenient, medium aggressivity requires treatment in the near future before the condition escalates further, and low aggressivity may not require treatment, but vigilance through ongoing routine testing should be practised and is recommended".

Other water quality parameters, such as iron concentration, may also be used as an indicator of ongoing biofouling. For instance, when elevated iron levels are observed in a well, the maturing IRB biofilm is probably sloughing and some action should be taken to remove or reduce the amount of that biofilm. A well treatment could initially consist of shock chlorination or could eventually require more robust well rehabilitation techniques, including UAB^TM .

Record keeping is essential so that any decline in performance will not go undetected. The well's specific capacity should be measured at least monthly. The measured specific capacity should then be compared with the original specific capacity. As soon as a 10 to 15% decrease in specific capacity is observed, steps should be taken to determine the cause and to correct the problem.

The City of North Battleford should measure static and pumping water levels in Well 15 on a monthly basis to determine changes in specific capacity. Routine BART tests should be conducted every 3 or 4 months to determine the aggressivity of the bacteria. Additional monitoring comprised of BART samples and pump tests should be conducted on Well 15 as soon as there is a reduction in specific capacity below 0.8 L/s/m (3 igpm/ft).

The City should also put a similar monitoring program in place for the remainder of its wells to safeguard their infrastructure investment.

5.2 REHABILITATION DECISIONS

Many economic factors, in addition to the intrinsic value of the water itself, should be taken into account when making the decision to rehabilitate an existing well or to construct a new one. These factors include: the direct cost for the rehabilitation program in comparison to the cost of a new well, the time required to rehabilitate an existing well or to drill and place a new well into service, the projected lifespan of the new well, the projected lifespan of the existing well if rehabilitated, the projected lifespan of the existing well if not rehabilitated and the costs of operating each well. Some of these factors were accounted for in the economic calculations presented in Appendix D of this report. Also, if the new well is completed in the same aquifer as the existing rehabilitated well, the problem will likely recur. In that case, the new well would require the same preventative maintenance program that the existing well would receive, or the new replacement well would be expected to fail at the same rate as the original.

Current well rehabilitation theory suggests that treatment or rehabilitation should take place as soon as there is a decrease in the well's performance. In any case, well rehabilitation procedures should be initiated before the specific capacity has declined 25% from the original specific capacity. Industry experience dictates that a well that has a specific capacity that is less than 75% of the original specific capacity often requires much larger expenditures for chemicals and labour without ever regaining the original performance. Often, it may be impossible to completely restore the original specific capacity of wells that are allowed to deteriorate further, even when using the best chemicals and rehabilitation techniques available.

5.3 ONGOING MAINTENANCE FOR WELL 15

Well 15 must be shock chlorinated using a 1000 mg/L chlorine solution made up of 40 litres of 12.5% liquid sodium hypochlorite every six months. The use of calcium hypochlorite should be restricted, as it may cause calcite precipitation in the well or gravel pack, leading to a severe chemical incrustation problem. The existing well pump may be used to surge the chemical out

into the formation by rawhiding, which involves turning the pump on until water in the pipe reaches the surface, shutting the pump off, and letting the water in the drop pipe to fall back into the well (thereby surging the aquifer). The sodium hypochlorite must have an overnight contact time to traumatize the bacteria. When pumping clean the next morning, the pump must be turned on at no more than 80% of existing maximum yield and pumped to waste for 10 minutes. The pump should then be turned off and the water level in the well should be allowed to return to within one foot of static water level. Repeat the process. Intermittent rawhiding as described above could also be performed to help dislodge and remove any loosened biofilms. This surging process can be completed three or more times (the more, the better) and then the well can be pumped until the water is clear.

6.0 CONCLUSIONS

1. The UAB^TM treatment process appears to be a viable treatment method for the City of North Battleford well field. The 1997 treatment result for Well 15 is much better than any of the previous treatments applied to this well. The 1997 UAB^TM treatment increased the post-treatment specific capacity to 176% of the pre-treatment specific capacity. The best conventional acid treatment only increased the post-treatment specific capacity to 118% of its pre-treatment specific capacity (see Figure 5). With refinements to the treatment process, UAB^TM should be even more effective in rehabilitating the City of North Battleford well field.
   
   
2. The increase in available water supply from Well 15 due to the 1997 UAB^TM treatment is about 129,166 m³/yr, 77% over the pre-treatment well yield. The City has the potential to save about $50,000/year by treating this volume of groundwater instead of surface water.
   
   
3. Unfortunately, Well 15 was extremely biofouled and had lost about 90% of its original production capacity before the UAB^TM treatment. Therefore, Well 15 will probably never recover to its original specific capacity. It is believed that the maximum specific capacity that could be achieved for this well is about 2.3 L/s/m (9 igpm/ft) or 50% of the original specific capacity. This may be achieved with further UAB^TM treatment, as proposed for 1998.
   
   
4. Monitoring of the specific capacity in Well 15 revealed that the specific capacity peaked about one month after treatment (Figure 6). This lasted for about two months, at which time an apparent decline in specific capacity occurred. The latest data appear to show that the specific capacity has stabilized at 0.8 L/s/m (3.2 igpm/ft). Further data need to be collected to validate this trend.
   
   
5. Water chemistry and microbiological tests reveal that the 1997 UAB^TM treatment was effective in reducing both the bacterial aggressivity and iron concentrations in water from Well 15. BART test results show that, as of February 2, 1998, the post-treatment bacterial aggressivity has been greatly reduced from the pre-treatment levels, with the IRB and SRB currently showing only mild aggressivity. In addition, the decrease in iron concentration is significant, although the post-treatment concentrations remain much higher than those in most of the other wells. The manganese concentration was not significantly affected and remains much higher than the values found in most of the other wells in the well field.

7.0 RECOMMENDATIONS

1. Monitoring and maintenance plans should be implemented for the City of North Battleford well field to maintain the integrity of the infrastructure and to reduce capital outlay and operating costs over the long term. The City of North Battleford should follow the monitoring and maintenance program for Well 15 as specified in Section 5.3 of this report. In addition, similar programs should be implemented for each of the City's wells.
   
   
2. Further rehabilitation of Well 15 is recommended. Additional well treatment should substantially improve the well's specific capacity and reduce the treatment requirements for the groundwater. The City should also realize a large economic benefit from further treatment of this well.
   
   
3. It is recommended that design of any additional refinement of the UAB^TM treatment process investigate the possibility of a further reduction of iron and manganese levels in Well 15. The analysis performed on the purge water indicates a high iron concentration in the purge water sample, indicating that the treatment technology was effective in dissolving iron down the well. However, the iron concentration in water withdrawn from Well 15 is still significantly higher than the concentrations in the majority of the other wells (see Table 1). Also, low manganese concentrations in the purge water may indicate that the manganese deposits in the biofilm were not readily removed during the treatment.

8.0 REFERENCES

Cullimore, R., 1993. Practical Manual of Groundwater Microbiology. Lewis Publishers, Chelsea, MI.

Cullimore, R., 1997. DBI Interim Report to PFRA. Droycon Bioconcepts Incorporated, Regina, Saskatchewan.

Cullimore., R. and T. Legault, 1997. Microbiological Investigations of Water Wells in the Municipal District of Kneehill, Alberta. Droycon Bioconcepts Incorporated, Regina, Saskatchewan.

DBI, 1998. Biological Testing in Support of the Water Well Rehabilitation Initiative - Draft Report to Leggette, Bradshears and Graham. Droycon Bioconcepts Inc., Regina, Saskatchewan.

Helweg, O.J., 1982. Economics of Improving Well and Pump Efficiency. Groundwater Vol.20, No.5.

Keevill, B., 1997. Implementation of the BCHT^TM (Blended Chemical Heat Treatment) Process to Rehabilitate Clogged/Biofouled Groundwater Wells. Fourth Year Engineering Thesis, University of Regina, Saskatchewan.

Keevill, B., 1998. Implementation of the UAB^TM Process to Rehabilitate Biofouled Water Well #15 for the City of North Battleford (A Pilot Project). Droycon Bioconcepts Incorporated, Regina, Saskatchewan.

PFRA and DBI, 1997. Development of Ultra Acid-Base (UAB^TM ) Water Well Treatment Technology. Prairie Farm Rehabilitation Administration and Droycon Bioconcepts Incorporated.

Smith, S., 1995. Monitoring and Remediation Wells. Lewis Publishers, Boca Raton, Florida.

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WELL 15: ECONOMIC CONSIDERATIONS FOR WELL REHABILITATION

There are several ways that cost savings from well rehabilitation can be calculated. One method is to calculate the cost savings associated with reduced power requirements corresponding to decreased water level drawdown within the well for a given pumping rate. Another method of calculating the economics of the well rehabilitation must also be looked at, namely the benefit of the increase in available water supply from the well. Calculations for both of these methods are outlined in the following sections.

D1 - CALCULATING ENERGY SAVINGS DUE TO DECREASED DRAWDOWN

The energy savings at a given flow rate can be calculated by subtracting the post-rehabilitation energy costs from the pre-rehabilitation energy cost at that flow rate. The electrical energy used by an electric motor coupled with a pump can be calculated with the following formula (Helweg, O.J., 1982. Economics of Improving Well and Pump Efficiency. Groundwater, Vol.20, No.5):

where:

KW = energy used (kwh/h)
Q = pump discharge (USgpm)
s = drawdown (feet)
SWL = static water level, including system pressure (feet)
e_o = overall "wire to water efficiency" of pump and motor (= e_m x e_p)
0.746 = conversion of horsepower to kilowatts

The total cost of operating the motor and pump is calculated as follows:

where:

TC = total cost of energy used ($/h)
KW = energy used (kwh/h)
C = cost of energy ($/kwh)

D2 - ENERGY SAVINGS FROM DECREASED DRAWDOWN AT 70 IGPM

Power requirements are less with smaller water level drawdowns because the head that the pump motor has to work against is less. Therefore, the amount of energy expended is less.

D2.1 Assumptions

• well will continue to be pumped at 70 igpm (ie Q = 84 Usgpm)
• pump is run 24 hours/day, 365 days/year
• rehabilitation effects will last with appropriate well maintenance
• static water level is 4.49 m (14.73 ft ) below ground and system back pressure is 25 psi (57.8 ft) according to Ivan Katzell (City of North Battleford, Plant Foreman); therefore, SWL in Equation 1 = 72.5 ft)
• e_o = e_m x e_p = (0.9)(0.37) = 0.33 (pump data obtained from Ivan Katzell)
• cost of electricity for City of North Battleford is $0.0327/kwh (ie C = 0.0327)

D2.2 Yearly Energy Savings From 1997 Rehabilitation

Cost of pumping at 70 igpm before 1997 rehabilitation:

Drawdown (s in Equation 1) Energy Used (KW from Equation 1) Total Cost of Energy (TC from Equation 2)= $0.170/h = $1489/yr

35.83 ft (10.92m) 5.20 kwh/h $1489/yr

Cost of pumping at 70 igpm after 1997 rehabilitation:

Drawdown (s in Equation 1) Energy Used (KW from Equation 1) Total Cost of Energy (TC from Equation 2) = $0.147/h

21.25 ft (6.48 m ) = 4.50 kwh/h = $1288/yr

Energy Savings:

cost of pumping before: cost of pumping after:

$1489/yr - $1288/yr =$201/yr

The total yearly energy savings from the 1997 UAB^TM well treatment is approximately $200 at a flow rate of 70 igpm. The energy savings alone therefore do not provide economic justification for well rehabilitation for this well field. The amount of available drawdown in the well field is very small and therefore well rehabilitation cannot possibly cause the large changes in drawdown that would be necessary to provide substantial cost savings at the City's current electrical rate.

D3 - BENEFIT FROM INCREASE IN WATER AVAILABILITY FROM WELL 15

The benefit derived from the increased availability of water can be approximated by using the alternative cost method, which determines the cost of obtaining water from the next best source (Helweg, O.J., 1982. Economics of Improving Well and Pump Efficiency. Groundwater, Vol.20, No.5). Therefore, the benefit of obtaining water from a given source is approximated by subtracting the cost of obtaining water from that source from the cost of obtaining water from the next best source.

D3.1 Assumptions

• that the extra water supply from Well 15 is required and if not obtained from Well 15 would have to be supplied from the North Saskatchewan River.
• rehabilitation effects will last with appropriate well maintenance
• Well 15 will be operated so that drawdown will remain at pre-treatment level of 10.92 m
• specific capacity before UAB^TM treatment (SC_before) is 1.96 igpm/ft as calculated by PFRA and DBI from pump test performed on October 6, 1997
• specific capacity after UAB^TM treatment (SC_after) is 3.47 igpm/ft as calculated from pump test performed by City of North Battleford on January 12, 1998
• cost of treating surface water is $0.387/m³ more than treating groundwater: cost for treating surface water is $0.527/m³; cost for treating groundwater is $0.14/m³ (1996 data provided by Ivan Katzell)
• energy costs are negligible or are incorporated into the cost of treating the water

D3.2 Increase in Available Water Supply from UAB^TM Treatment

Pumping Rate Before UABTM Treatment

= SCbefore x difference drawdown = 1.96 igpm/ft x 35.83 ft = 70 igpm = 167,513 m3/yr

Pumping Rate After UABTM Treatment

= SCafter x difference drawdown = 3.45 igpm/ft x 35.83 ft = 124 igpm = 296,679 m3/yr

Increase in available water supply due to 1997 UAB^TM treatment is therefore 129,166 m³/yr., an increase of 77% over the pre-treatment well yield.

D3.3 Benefit of 1997 Rehabilitation from an Increase in Available Groundwater Supply

Benefit

= change in amount of surface water that needs to be treated x (cost of treating surface water - cost of treating groundwater) = 129,166 m3/yr x $0.387/m3 = $49,987/yr

The potential cost savings to the City of North Battleford from the 1997 UAB^TM treatment of Well #15 alone is therefore approximately $50,000 per year.

D3.4 Potential Benefit of Future Well Rehabilitation of Well 15

If Well 15 were to undergo further rehabilitation to the extent that a hypothetical well yield of 180 igpm (50% of the original 1990 well yield of 359 igpm) was made available, this well could possibly sustain a pumping rate of 110 igpm over the 1997 pre-treatment well yield. This converts to 262,485 m³/yr, assuming that the pump will be running constantly. If all of this additional water were used to replace the same volume of surface water, the cost savings to the city could be $101,581/yr (volume x $0.387/m³ cost difference between treating surface water and groundwater).