Disinfection is an important step in ensuring that water is safe to drink. Well disinfection is used to inactivate or control bacteria populations in a well and the distribution system. Disinfection is the inactivation or destruction of pathogenic organisms through the disruption of the organisms’ normal life processes. The objective of this work is to clean and/or disinfect entire borehole to prepare wells for pump installation. The last water sample was collected after the well disinfec-tion on that time. The results of water chemical analysis are presented in Tables 2-4, and there was nothing found against the specification requirements. After a reaction time of approximately 12 h, the well was cleaned from the sterilization solution by airlifting until chlorine concentration in the water reached 0 mg/l. Then through analyzing the test for samples of water after disinfection and sterilization the wells showed the Iron Bacteria were not seen and the Bacteria Species/Anaerobic Bacteria were absent.
The source of the water determines the characteristics of the water. Water sources, in order of decreasing quality, include springs, boreholes, sealed wells, hand-dug wells, streams, rivers, and lakes. Boreholes are wells drilled with a drilling rig, and like springs, tap groundwater sources that have been filtered through layers of soil and rock and are isolated from the surface. These sources may contain unpleasant color, odor or minerals but are generally free from pathogen contamination and, therefore, will not require disinfection. Sealed wells are shallow wells that have been sealed with cement around a pump to prevent contamination. However, contamination is possible, and sealed wells are often treated with chlorine. Hand-dug wells are typically contaminated. Wells become contaminated from contamination water entering the well from above, especially during flooding. Improper drainage (sloping in toward the well) also promotes well contamination.
In a paper published in 1894, Moritz Traube formally proposed the addition of chlorined of lime (calcium hypochlorite) to water to render it “germ-Free”. Two other investigators confirmed Traubes findings and published their papers in 1895 [
In the USA, the first use of chlorine for continuous disinfection of a drinking water supply took place in 1908 at Boonton Reservoir (on the Rock way River), which served as the supply for Jersey City, New Jersey [
Chlorine gas was first used on a continuing basis to disinfect the water supply at the Belmont filter plant, Philadelphia, Pennsylvania in 1913. Darnell’s work and the technological innovations by Dr. George Ornstein and the Wallace & Tiernan Company became the basis for present systems of chlorination of municipal water supplies. By 1941, disinfection of U.S. drinking water by chlorine gas had largely replaced the use of chloride of lime [
Depending on the PH, hypochlorous acid partly dissociates to hydrogen and hypochlorite ions:
In acid solution, the major species are CL2 and HOCL while in alkaline solution effectively only CLO− is present. Very small concentrations of
Natural ground water from all but very shallow aquifers is considered free from pathogenic (disease causing) bacteria and viruses (Bouwer, 1984) [
Disinfection is the inactivation or destruction of pathogenic organisms through the disruption of the organisms’ normal life processes (Connell, 1996) [
The objective of this study includes the proper water supply system preparation, including the sanitary completion of water well, the cleaning of existing wells, and the proper development of new wells, through flushing of the water supply, by treatment with a properly prepared chlorine solution, collection and analysis of water samples.
The introduction of microbial contaminants, into newly constructed or repaired wells can be minimized by practicing good general sanitation during storage, transport, handling and installation of well components.
Proper sanitation refers to cleanliness and taking precaution to prevent disease by not introducing bacteria and other contaminants while installing or repairing a water supply system. When the drilling contractor takes precautions to prevent the unnecessary introduction of contaminants into the well, the task of disinfecting the well becomes much easier.
The storage and transportation of well components and drilling supplies should be in good sanitation by the contractor starts at the shop and is important during the trip to the drilling site. The organization and storage of materials and equipment will benefit the contractor during the installation and final disinfection of the completed water supply system [
Prior to install the permanent pump CCTV survey was done to check the borehole conditions. The first CCTV survey (as final check) was carried out after the well A was completed from the depth of 144 m to the end of PHC, some areas were seen with minor biofouling, including the stripped pattern as shown (
1) Constituents of water-Natural waters represent complex solutions of many substances, most of which can be ignored, but some of which influence chlorination as follows:
a) Suspended solids: may shield bacteria from the faction of chlorine.
b) Organic Matter: reacts with chlorine and removes it from the water so that it no longer has disinfecting properties.
c) Ammonia-reacts with chlorine to form a chlorine compound (chloramines) having much lower disinfecting qualities than chlorine itself.
d) Nitrates, Manganese and Iron-react with and remove chlorine and may produce a false color when testing water for chlorine content.
2) Temperature―The temperature of water marked by affects the disinfecting action of residual available chlorine. Other things being equal, chlorination is most effective with high water temperatures. At lower temperatures, bacterial kill tends to be slower and higher residual concentrations are needed. The effect of low temperatures is greater with combined available chlorine than with free available chlorine, 1890, 1978.
3) PH―The PH of the water affects the disinfecting action of chlorine, particularly combined available chlorine residual that the disinfecting action of chlorine is more efficient at lower PH values of the normal PH range of water supplies.
4) Time-concentration, these two mutually related factors take into consideration the period of reaction time available for disinfection and the quantity and Kind of chlorine residual. A greater concentration acting over a longer period of time must be provided, on the other hand, if free available chlorine residual, an active disinfectant, is to be maintained the reaction period can be correspondingly less. The minimum contact time should be 30 minute and preferably with an undesirable concentration of residual chlorine.
e) Chlorine Dosage
The amount of chlorine needed to accomplish disinfection or other treatment objectives, depends on the chlorine demand of the water, the amount and kind of chlorine residual desired, the time of contact of the chlorine with the water and the volume of flow to be treated [
Chlorine feed rate = chlorine Dosage (mg/L) * flow (8.34) lb/gal
Pounds per day Percentage of free chlorine available
1 mg/L = 8.34 lb of free chlorine per million gallons
1 mg/L = LPPM.
1) Stock solution: the quantity of hypochlorite solution prepared at one time for the stock solution should be sufficient to last for about two weeks. A common strength for the solution to be fed into the system is 1% available chlorine; this means that every gallon, or 8.34 lb., will contain 0.0834 lb., or 1.34 oz., of active chlorine. If 70% hypochlorite is used, each gallon of 1% solution will contain 1.34/0.7, or 1.92 oz. of material. The weights in ounces of hypochlorite required to chlorinate various quantities of water from a 1 mg/L to a 200 mg/L dosage. The gallons of water needed to prepare a 1% solution using this quantity of hypochlorite, is found by divided the weight in ounces by 1.92 in the case of 70% hypochlorite.
2) Feed Rate: The rate at which stock solution is fed into the system should be based on the actual pump age, in gallon per minutes, and not on the average over-all 24 hour consumption. The volume of 1% chlorine solution needed per minute to furnish a 1 mg/L chlorine dosage when injected into a pipe line following 1000 gpm is:
After constructing or repairing a well or pump, the entire well and pumping system must be disinfected in order to kill harmful microorganisms (germs and bacteria) that may be on the well casing, gravel, soil, rising main, pumping rod or in the water from the digging operation.
A life water well was just drilled to a depth of 500 to 550 meters (1640.5 to 1804.5 fetes) [
Calculation of volume for disinfection & sterilization
1-Determine the volume for water in the well.
Area of circle = Π*r2
r: Radius of 18 5/8 (casing diameter 18 5/8)
a) r = 18 5/8 = 47.30 cm = 0.473 m
Area = 3.14 * 0.473 * 0.473 = 0.702 m2
Height of water column = well depth?depth to water (water level) = 550 - 126.92 = 369.38 m
Height of water column = 369.38 m
b) Volume = Area * Height = 0.702 m2 * 369.38 m = 259.30 m3
Volume = 259.30 * 1000 l/m3 = 259304.7 L
water level 126.92 m, open hole 171/2 OD length 169.85 m T.D (m) 550 casing l85/8 OD length 169.85 m
1-calculations of volume for disinfection & sterilization
A-volume inside 185/8 OD PHC section Height of water 315 - 126.92 = 169.85 m, 169.85 * 0.159 m3/m = 27.117 m3
B-volume inside 103/4 OD screen section 176.08 * 0.05851 m3/m = 10.302 m3.
C-volume inside 10 3/4 casing 63.32 * 0.05025 m3/m = 3.182 m3
D-volume inside gravel pack (GP volume * porosity 30%) = 31.8 m3 * 30% = 9.540 m3
Total volume = 50.141 m3
2-Quantity of calcium Hypochlorite for free chlorine, dosage at 50 ppm in casing and screen sections.
Total volume × 0.08 kg/m3 = 50.141 * 0.080 = 4.011 kg
-Quantity of calcium hypochlorite for free chlorine dosage at 100 ppm in casing sections.
Quantity = total volume * 0.160 kg/m3 = 69.236 * 0.160 kg/m3 = 1107 kg
Program 1:
Mixed water 56 m3, Calcium Hypochlorite = 4.48 kg
Pumping Steps #7 by 8 m3 of solution
Program 2:
Calcium Hypochlorite tablet dosage at 50 ppm:
Sterilization Test information-Used: Mixed water 58 calcium Hypochlorite 4.7 kg Start Pumping as following:
1st step 8 m3 at depth 533 m
2nd step 8 m3 at depth 467 m
3ed step 8 m3 at depth 425 m
4th step 8 m3 at depth 339 m
5th step 8 m3 at depth 317 m
6th step 8 m3 at depth 271 m
7th step 8 m3 at 209 m
8th step 0 m3
Dead volume 2 m3
Calcium Hypochlorite comes in strengths ranging from 30 - 75 percent available chlorine 70 percent most common). Chlorine is a very reactive substance. When added to a well, it first combines with inorganic compounds (hydrogen sulphide, ferrous iron, manganese) there no disinfection in this stage. After these compounds have been reduced, remaining chlorine then reacts with organic matter (algae, phenols and slime growth). After the demand exerted by inorganic and organic compounds has been met, chlorine will combine with nitrogen compounds (Primarily ammonia) to form chloramines. This combined chlorine form results in long lasting disinfection.
During the contact time the chlorine residual should be maintained in the water supply system for 4 to 12 hours (Coombs, 2001) [
From on site measurements, however, chlorine has also found application for a variety of other water treatment objectives, such as, the control of nuisance organisms, oxidation of taste and odor compounds, oxidation of Iron and manganese, color, removal, and as a general treatment aid to filtration and sedimentation processes (Connell, 1996; Williams and Culp, 1986) [
Analysis | Concentration mg/l | Time min | event |
---|---|---|---|
1 | 50.00 | 7 - 8 | After start of air lift pumping |
2 | 4 .00 | 8 - 10 | 120 min after start of air lift pumping |
3 | 0.0 | 10 - 15 | 300 min after start of air lift pumping |
4 | 0 .0 | 15 - 19 | 240 min |
12 hours during final Inspection |
Water samples for chemical analyses were collected from the sampling tap during SRPT. The samples were taken 1 hour and 23 hours after the start of the test. Both samples were analyzed for physical parameters, major and minor ions. The second sample was, in addition, analyzed for bacteriological parameters. The two samples were received by the Laboratories and Water Quality Sector, Water Authority of Jordan, Amman. On-site measurements are presented in
A third sample was collected after well sterilization and analyzed (
Laboratory Analyses of the Jordanian Drinking Water Standards are based on standards from the World Health Organization. As the Jordanian standards do not mention threshold values for certain parameters, in such a case the values stipulated in the EU guidelines from 1998 are used as reference [
The results of the laboratory analyses of the three samples taken are presented in
The total dissolved solids 320 mg/l are low and typical of low mineralized groundwater from sandstone aquifer. These values correspond to the electrical conductivity, with values between 370 and 339 μS/cm. The threshold value for manganese (0.1 mg/l) is exceeded on both samples, with concentrations of 0.27 and (0.48 mg/l) aerobic.
The bacteriological analyses after 23 hr of steady rate pumping show the presence of aerobic 1981). The turbidity is normally residuals of drill cuttings and/or drilling fluids that have been pushed out into the formation surrounding the borehole during the well construction process. Turbidity levels for common water sources are given in
The turbidity of well water is quite low, Sand content, turbidity, pH, temperature and EC were measured during airlift discharge). The acceptance criteria were met for each discharge rate: i.e. Turbidity < 0.2 NTU and sand content 0 ppm, after completing airlift pumping and backwashing, simultaneous swabbing/airlifting, until the acceptance criteria were met EC < 383 μS/cm and sand content 0 ppm. These results illustrated in
It can be expected that future use of the more turbid surface water will increase relative to well water usage (Feachem, Mc Garry, and Mara, 1977) [
On site measurements it was obtained the following results after sterilization which illustrated in
From
Parameters | 1st sample | 2nd Sample |
---|---|---|
Temperature [˚C] | 30.0 | 30.3 |
Electrical Conductivity [μS/cm] | 370 | 339 |
PH | 7.3 | 7.6 |
eH [m V] | 90 | 120 |
Turbidity [NTU] | 4.41 | 2.48 |
O2 [mg/l] | 4.04 | 5.06 |
H2S [mg/l] | 0.26 | 0.13 |
CO2 [mg/l] | 80 | 107 |
Temperature ˚C | Ec µs/cm | PH | eH (mv) | O2 mg/l | Turbidity Ntu | H2S | CO2 |
---|---|---|---|---|---|---|---|
29.6 | 289 | 7.79 | 43 | 7.25 | 0.21 | 0 | - |
Odour | NO | color | no | - |
Component | Result | Unit | LRV |
---|---|---|---|
Electrical conductivity | 383 | µs/cm | 2 |
Total Dissolved Solids | 260 | mg/l | 20 |
Hardness | 130 | mg/l | 15 |
Alkalinity | 102.50 | mg/l | 1.70 |
Turbidity | 2.35 | Ntu | 0.20 |
Calcium | 37.20 | mg/l | 0.30 |
Magnesium | 6.12 | mg/l | 0.30 |
Nitrate | 9.89 | mg/l | 0.20 |
Ammonium | 0.01 | mg/l | 0.01 |
Iron | 0.63 | mg/l | 0.10 |
PH | 7.66 | unit | - |
Iron Bacteria | Were not seen | - | - |
Bacteria Species/Anaerobic Bacteria | Absence | - | - |
Extended pumping normally clears the water of turbidity, and shown the turbidity of well water after sterilization is quite low 0.21, and Hypochlorite acid (HOCL) will form in waters ranging from PH 6.5 - 7.79. As the PH increase above 7.5 affects disinfection speed with high temperature provide to fast disinfection. Nitrate concentrations above 10 mg/l can cause blood disorder in infants (blue baby disease). Elevated levels indicate that mature, sewage, or nitrogen fertilizers are reaching the source. If nitrate levels above 45 mg/l, (10 mg/l nitrates as nitrogen) persist, the source of nitrate animal confinement areas, privies should be determined and relocated. The nitrate concentration is above 1 mg/l the water must not be given to infants and a different source (boiled for disinfection).
The total dissolved solids 320 mg/l are low and typical of low mineralized groundwater from sandstone aquifer. These values correspond to the electrical conductivity, with values between 370 and 339 μS/cm. The threshold value for manganese (0.1 mg/l) is exceeded on both samples, with concentrations of 0.27 and 0.48 mg/l aerobic. The turbidity of well water is quite low, sand content, turbidity, pH, temperature and EC were measured during airlift discharge. The acceptance criteria were met for each discharge rate: i.e. Turbidity < 0.2 NTU and sand content 0 ppm. The analyses test for samples of water after disinfection and sterilization the wells showed the Iron Bacteria were not seen and the Bacteria Species/Anaerobic Bacteria was absent.
Mehaysen Ahmed Mahasneh, (2016) Disinfection Water Wells and Sterilization. Computational Water, Energy, and Environmental Engineering,05,38-46. doi: 10.4236/cweee.2016.52004