Physico-Chemical and Microbiological Study of Piped Water Distribution Systems in an Urban City

 

S. D. Garway1*, Dattatraya G. Garway1, M. Raina2 and G.H. Pandya3

 1Research and Development Division, Anacon Laboratories, 60, Bajiprabhu Nagar, Nagpur 440 033 (India)

2Director-Scientist-F, Ministry of Environment Forests, Govt. of India, New Delhi (India)

*Corresponding Author E-mail: pandyagh@rediffmail.com

 

ABSTRACT:

The water distribution system is a critical component of every drinking water supply authority. Its primary function is to provide the required water in quantity and quality to the consumers. Although, water is treated before supply to the consumers, it gets degraded during its distribution. It may undergo chemical and biological reactions during distribution because of leaks and improperly maintained storage facilities. Special problems arise at the consumers tap due to improper plumbing, which is not under the control of the municipal authorities. Most of the distribution systems are aging and becoming more vulnerable to  breaks and leaks because they are underground and out of sight. The purpose of this paper  is to: (1) identify trends relevant to the deterioration of drinking water quality in water supply distribution systems in various zones of the city, (2) identify and prioritize issues of greatest concern for distribution systems, and (3) apply Total Coliform Rule for microbial examination of water samples, (4) study  raw water undergoing treatment at  various treatment plants in the city and analyse water stored at various reservoirs (5) monitor the water supply system in 10 zones of the city.

 

More than 3000 samples were analysed in monsoon season. Samples with Total coliform count greater than 16 are considered as “Unfit” for drinking purpose. It is observed that the Total coliforms are >16 in the raw water received at the water treatment plants. Further, the samples were analysed for Thermotolerant count and the samples tested positive for the months of June and September respectively. The results indicate that during the routine monitoring, total coliform count in eight zones of the City exceed the TCR criteria of EPA. After initiating actions of proper chlorination improvement in microbial quality of six zones were observed. Improvement in water treatment at various stages of water treatment plants was also observed. There was a dramatic reduction in Gastroenteritis cases in the city from 786 in 2007 to 157 in 2008.  The above surveillance study clearly indicates that there is a substantial improvement in water quality in the distribution system, which confirms with the observation of Health Department of Nagpur Municipal Corporation that the large proportion of disease cases was waterborne. Some factors contributing to contamination of water and methods to control growth of microorganisms in the pipes are also discussed

 

KEY WORDS: piped water, microbiology of water, total coliforms, thermotolerant, urban water supply.

 

 

INTRODUCTION:

Piped water supply systems are generally buried complex materials and are relatively difficult to operate and maintain. However, they are important as a water resource and one has to ensure the quality of water carried through these systems. A drinking-water distribution system provides a habitat for microorganisms, which are sustained by organic and inorganic nutrients present on the pipe and in the conveyed water.

 

A primary concern is therefore to prevent contamination from faecal material that might build up near pipes or contaminate surface or Safe Piped Water soil water. Generally, bacteria present in the water and on surfaces are harmless, but they are at the base of a food chain for other free-living organisms such as fungi, protozoa, worms and crustaceans. These organisms may be present in a distribution system, even in the presence of residual disinfectant, and the water can still be free of health risks. However, excessive microbial activity can lead to deterioration in aesthetic quality (e.g. tastes, odors and discoloration) and can interfere with the methods used to monitor parameters of health significance. Therefore, additional treatment may be needed to control the quality of the treated water in a distribution system, to prevent excessive microbial growth and any associated occurrence of larger life forms [1].

Maintaining good water quality in distribution also depends on the operation and design of the distribution system and requires maintenance and survey procedures to prevent contamination, and to remove and prevent the accumulation of internal deposits. Performing any work on the system that entails contact with conveyed water or internal surfaces increases the risk of contamination. Such situations require well-documented hygienic working practices. The practices are also relevant to the prevention of problems of discolored water, odors and tastes. The provision of tap water that is both aesthetically pleasing and safe is important, because it will discourage the consumption of alternative supplies that may not be safe, even if they appear to be so. The traditional approach to verifying the microbial safety of piped public water supplies has relied on sampling strategies based on the end-product i.e. tap water. Government-enacted laws in many countries have set guidelines or regulations describing limits for microbial content and the normal rationale for these is that historical data have shown compliant water to be safe. However, the effectiveness of some of these guidelines and regulations has been challenged by epidemiological studies. Analysis of data accumulated over the 20th century has suggested that some of the microbial standards (e.g. heterotrophic plate count, total coliforms and thermotolerant coliforms) have little predictive value for public health purposes in certain situations [2]. Outbreaks have sometimes occurred when drinking water met such standards [3], [4]. This is either because some pathogens are more difficult to remove or have a higher level of resistance to disinfection processes than the indicator microorganisms stipulated in the standards, or because the sampling frequency is too low to reveal  contamination,  particularly when it is transient.

The identification and enumeration of microorganisms is slow, and hence is not suitable for early warning or control purposes. Sampling and monitoring the microbial quality of water supplied to the consumer can only verify that water is safe when it was supplied and ingested.

 

 

Continuous monitoring of water distribution for its potability assumes significance. The Nagpur Municipal Corporation, Nagpur requested Anacon laboratories to conduct studies related to monitoring of water quality in various water distribution zones of the city as well at the water treatment plants and intake points of the water supply to the city.

 

 

The population of the city is increasing rapidly. The pace of expansion of various schemes does not commensurate with the water demand of the population. This has resulted in increased load on the existing water distribution systems and in reduction in water pressure in various parts of the city. An investigation of water quality supplied to Nagpur city through a distribution network was continuously monitored for over a year for various physico-chemicals and bacteriological parameters. Residual chlorine and Bacteriological parameters were continuously examined to find out the effectiveness of chlorination performed at various water treatment plants of the city.

The objective of the paper is to study the water supply and distribution system of Nagpur city, analyze the quality of water at the inlet source, at the water treatment plants, estimate the residual chlorine and bacteriological levels at the tail end points, and suggest remedial measures to disinfect the water at the source supply end. The results were analyzed critically to identify the affected areas.

 

MATERIAL AND METHODS:

The physico–chemical analysis of water samples collected from various intake reservoirs, treatment plants was carried out using standard methods of analysis and following IS:10500,1981 guidelines[5]. The microbiological examination of water samples was carried out as per IS: 1622-1981[6]. It may be mentioned here that potability of public drinking water supplies depends mainly on the presence /absence of total coliform per 100 ml of drinking water. Hence, for monitoring the quality of water in the distribution system of the Nagpur city, stress was laid on testing water samples for their bacterial content. Initially on-spot analysis of residual chlorine [7] was conducted and depending on the results, samples were subjected to microbiological tests. Two types of tests were conducted. The first being presumptive test for the enumeration of coliform bacteria in water samples and the second being a confirmatory test for coliforms as well as for faecal coliforms. The presumptive test required preparation of MacConkey Broth (Double Strength) media and confirmatory test required Brilliant Green Bile Lactose Broth media.   All the reagents used were of Bacteriological Grade (HiMedia, Mumbai).The MacConkey Broth (Double Strength) media was prepared using Peptone 200gm,Lactose 100g, Sodium Chloride 50g,Bile Salt 50g, pH  7.4, Neutral Red 10ml (1%) ,Distilled water 1000ml. The chemicals required for confirmatory tests were Peptone 10g, Lactose 10g, Bile Salt 20g,Distilled water 1000ml, pH 7.4 and Brilliant Green 13ml (0.1%).

 

RESULTS AND DISCUSSION:

One of the important aspects of preventing microorganisms from entering drinking water is protection of the water source. This requires control of land use within the catchments or recharge area. This in turn reduces load on water treatment plant so that water of acceptable quality is provided to the consumers.

 

If one examines the water treatment process at the treatment plant the water, leaving water treatment plants should meet stringent criteria to provide assurance to the community that the bacteriological content of drinking-water leaving treatment plants contains only very low levels of heterotrophic and aerobic spore-forming microorganisms. Low levels of these organisms indicate that the treatment and disinfection processes are effective in removing or inactivating most pathogens at this level of treatment, total coliforms, thermotolerant coliforms and E. coli should be absent. They are much less resistant to disinfection than other heterotrophic and aerobic spore-forming microorganisms, and their presence would be an immediate indication of an unacceptable quality. Their presence may indicate inefficient coagulation, inefficient filtration (e.g. failure in filtration, backwash recycling and poor maturation of filters) and poor disinfection (e.g. no free-residual disinfectant and short contact times). Pathogenic microorganisms that evade treatment and enter the distribution system may survive and be the source of an important level of endemic disease in the population. Therefore, the selection of appropriate processes for the removal of pathogens and the adoption of Water Safety Plan principles in operating these treatment barriers is important for safe water supply.

 

Water samples collected during pre and post-monsoon season (June to September) at one of the water treatment plant located at Kanhan was analysed for physico chemical and bacteriological parameters. The results are summarized in Table 1. Total Coliform Count was considered as indicator of the general quality of treated drinking water supplies. The total coliform bacteria test is a primary indicator of "potability”, suitability for consumption, of drinking water. It measures the concentration of total coliform bacteria associated with the possible presence of disease causing organisms. Coliform bacteria are a natural part of the microbiology of the intestinal tract of warm-blooded mammals, including man.  Coliform bacteria can also be found in soil, other animals, insects, etc. The total coliform group is relatively easy to culture in the lab, and therefore, has been selected as the primary indicator bacteria for the presence of disease causing organisms in the water supply and distribution system.

 

Total coliform counts were thus determined in raw water samples at the treatment plant. Samples with Total coliform count greater than 16 are considered as “Unfit” for drinking purpose. Samples found unfit were subjected to further analysis to identify Thermotolerent positive bacteria. These are coliform groups present in water due to faecal contamination i.e. discharge of faeces by human and other animals in water source. Coliforms are the members of the family Enterobacteriaceae that includes E.coli, Enterobacter aerogenes and Klebsiella pneumonia. These bacteria make up about 10% of intestinal microorganisms of the humans and other animals and, therefore, have found wide spread as indicator organisms as an index of possible water contamination. If such bacteria are not detectable in water in 100ml, then the water can be said as potable water.

 

It is observed from Table 1 that the Total coliforms are >16 in the raw water received at the treatment plant during the months of June to September. Further the samples were analysed for Thermotolerant count and the samples tested positive for the months of  June and September respectively. The above observation indicates that raw water is contaminated at the intake point and needs treatment prior to its distribution to the consumers.Physico-chemical analysis indicates that the Turbidity results are mostly high and above the desired limit for drinking water. The Aluminum concentrations were also above the desirable limit. Subsequently, the authorities were informed to carry out proper chlorination at the treatment plant to make water fit for drinking.

 

Water Quality at Treatment Plants:

The raw water supplied to the city is treated at five water treatment plants viz Pench 1, Pench 2, Pench 3, Gorewada, and Kanhan.   Investigations were also carried on quarterly basis about the microbiological status of raw water, settled water, filtered water, and treated water from various units of  five water treatment plants of the city The samples were analysed for total coliform and thermo tolerant bacteria. The results of raw water, settled water, filtered water and treated water analysed for the months of May, August and November are summarized in Table 2.  It is observed that the raw water at all the treatment plant showed the presence of total coliform (TC).Even the settled and filtered water at some of the treatment plant indicated the presence of TC During summer season the water levels at the intake points of treatment plants are quite low resulting in withdrawal of contaminated waters. However, after filtration and providing chlorination at the treatment plant, the coliform were found to be absent. Thermotolerent bacteria were absent in water samples collected after undergoing treatment in the plant.

 

 

TABLE 1 : Physico-chemical and Bacteriological analysis of Raw water at Kanhan Water Works

S.No

Parameter

Units

Results

June

July

Aug

Sept

Limit

1

Apparent Color

Hazen

40

3

100

40

 

2

Turbidity

NTU

66

3.3

26.4

185

5

3

pH

 

7.67

8.45

8.17

7.96

6.5-8.5

4

Total Hardness

mg/L

107.19

128.08

128.08

104.08

300

5

Dissolved Iron

mg/L

0.30

0.14

0.22

2.62

0.3

6

Chlorides

mg/L

9.19

32.92

16.27

10.22

250

7

TDS

mg/L

165.77

252.85

260.34

188.34

500

8

Calcium

mg/L

34.63

28.82

30.42

35.22

75

9

Magnesium

mg/L

5.02

13.64

12.67

3.90

30

10

Aluminium

mg/L

0.25

ND

0.16

0.22

 

11

Sulphate

mg/L

6.54

18.32

17.44

18.32

200

12

Nitrates

mg/L

4.90

<0.4

<0.4

2.63

45

13

Fluoride

mg/L

0.20

0.20

0.3

0.2

1.0

14

Total Alkalinity

mg/L

118.68

171.83

142.81

109.38

600

15

Total Coliform

MPN/100ml

>16

>16

>16

>16

Absent

16

ThemoTolerent

MPN/100ml

Positive

Absent

Absent

Positive

Absent

17

TSS

mg/L

122.3

-

21

301.07

 

18

Residual Chlorine

mg/L

Nil

Nil

Nil

Nil

 

TC (Desirable Limit) : Absent, Permissible Limit : 10 MPN/100ml,   TT= Absent

 

TABLE 2: Microbiological status of Water Quality at Treatment Plants

Quarter

Treatment Plant

Sample

TC

TT

TC

TT

TC

TT

 

May

August

November

1

Pench I

Raw

>16

A

>16

A

>16

A

 

 

Settled

>16

A

>16

A

>16

A

 

 

Filtered

A

A

>16

A

>16

A

 

 

Treated

A

A

2

A

A

A

2

Pench II

Raw

>16

A

>16

A

>16

A

 

 

Settled

>16

A

>16

A

>16

A

 

 

Filtered

9

A

>16

A

>16

A

 

 

Treated

A

A

A

A

A

A

3

Pemch III

Raw

6

A

>16

A

>16

A

 

 

Settled

A

A

A

A

A

A

 

 

Filtered

A

A

A

A

A

A

 

 

Treated

A

A

A

A

A

A

4

Gorewada

Raw

>16

A

>16

A

>16

A

 

 

Settled

16

A

>16

A

>16

A

 

 

Filtered

9

A

>16

A

>16

A

 

 

Treated

A

A

A

A

A

A

5

Kanhan

Raw

>16

A

>16

A

>16

A

 

 

Settled

>16

A

>16

A

>16

A

 

 

Filtered

>16

A

>16

A

>16

A

 

 

Treated

A

A

2

A

A

A

A=Absent, TC=Total Coliform, TT= ThermoTolerent

 

 

Water Quality at Treatment Plants:

The raw water supplied to the city is treated at five water treatment plants viz Pench 1, Pench 2, Pench 3, Gorewada, and Kanhan.   Investigations were also carried on quarterly basis about the microbiological status of raw water, settled water, filtered water, and treated water from various units of  five water treatment plants of the city The samples were analysed for total coliform and thermo tolerant bacteria. The results of raw water, settled water, filtered water and treated water analysed for the months of May, August and November are summarized in Table 2.  It is observed that the raw water at all the treatment plant showed the presence of total coliform (TC).Even the settled and filtered water at some of the treatment plant indicated the presence of TC .During summer season the water levels at the intake points of treatment plants are quite low resulting in withdrawal of contaminated waters. However, after filtration and providing chlorination at the treatment plant, the coliform were found to be absent. Thermotolerent bacteria were absent in water samples collected after undergoing treatment in the plant.

 

Water Distribution systems:

The water supplied to the city is through Nagpur Municipal Corporation (NMC). On an average NMC supplies 470 MLD potable water to Nagpur City, Military Engineering Services and Cantonment Board, Kamptee. Water is also made available to consumers through ground water dug wells and bore wells. Places where there are no pipeline connections, water is supplied through tankers.

 

Two major water sources viz Kamptee Khairy reservoir on Pench river and Kanhan river are used to augment water supply to the city. About 170 Mm3 raw water is drawn from Kamptee- Khairy reservoir and 55Mm3 from the Kanhan River. The water drawn from these reservoirs is further treated at five different water treatment plants viz. Pench

 

stage -I (113 MLD), Pench stage –II (133 MLD), Pench Stage –III (100MLD), Old Gorewada (16 MLD) and Kanhan (108 MLD). The potable water is then supplied through Master Balancing Reservoirs (MBR) located at Seminary Hill (24.97ML), Govt House (22.74 ML) and Sitabuldi Fort (22.8 ML). The water for the city is stored in 43 reservoirs at 31 locations. The total capacity of stored water supply in reservoirs is 151, 79 ML. The city is divided into 10 distribution zones covering a distribution network of 1700 km.

 

Bacteriological quality of water was daily monitored at various municipal zones of the city. Samples were collected from the Inlet and outlet of various ESR of 10 Zones respectively. In order, examine the bacteriological quality of water supplied to the consumers, sampling locations at the tail end of the pipe lines were selected based on information received from the supervisor of respective zones. On-spot residual chlorine was measured at each tail end water supply location. Although residual chlorine test is a chemical test we included it under microbiological analysis as residual chlorine has great significance in presence or absence of microorganisms. Chlorine gas solution is being used as a disinfectant at water treatment plants. Residual chlorine which is defined as the amount of excess or residue of chlorine that remains in the water after disinfection must present in water throughout distribution system, as it will take care of any recontamination of water.  Chlorine is commonly used to maintain a residual. Its disinfecting power is a function of pH, because when chlorine is added to water it reacts to produce hypochlorous acid (HOCl):

 

Cl2 + H2O → HOCl + H+ + Cl-

 

The hypochlorous acid will dissociate to the hypochlorite ion (OCl-) as the

Water increases in pH:

 

HOCl → H+ + OCl-  

 

OCl-   → Cl-  +  O     

 

The hypochlorite ion is a less powerful disinfectant than hypochlorous acid. The disinfecting properties of chlorine in water are based on the oxidizing power of the free oxygen atoms and on chlorine substitution reactions. The mechanism of disinfection is illustrated in Figure 1.The cell walls of the pathogenic microorganisms are negatively charged. It can be penetrated by neutral hypochlorous acid, rather than by the negatively charged hypochlorite ion. Hypochlorous acid penetrates the slime layer, cell walls and protective layers of microorganisms and effectively kills pathogens. The microorganisms either die or suffer from reproductive failure.

 

In Europe, common target concentrations for free chlorine residual at the tap are 0.1–0.3 mg/l. In India, as per IS 10500 [5] there should be a minimum 0.2 ppm of residual chlorine present at the user end. At the higher value, consumers commonly detect the taste and odour of chlorine. However, detection levels vary widely between people and some can detect chlorine at much lower levels.

 

Around 50 consumers were daily monitored for residual chlorine in each zone of the city. On spot testing of samples indicating residual chlorine less than 0.2 ppm are separated and transported to laboratory for further microbiological examination. The bacterial safety of drinking water is monitored by testing for coliform bacteria. The samples are collected in sterilized sampling bottle .The bottle is completely sterilized. This assures bacteria in the bottle do not contaminate the sample. The use of any other container is discouraged. Instructions are provided to the persons on how to collect the water sample. They follow the instructions carefully to avoid outside contamination and to obtain a good representative sample. The sample is received at the laboratory within 6 hours after collection. On receipt at the laboratory, it gives the sample a number and the time of arrival is stamped on the accompanying form.

 

During monsoon season, more than 3000 samples were analysed for Bacteriological contents. Figure 2 illustrates the number of samples analysed per month during August to December. It is observed from Figure 2 that maximum samples were collected during monsoon season Aug-Sept. During this season, water is highly turbid and chances of contamination at the water intake point of reservoirs are quite high. The results were analysed so as to see whether it complies with the EPA Total Coliform Rule (TCR) [8] which is the maximum contaminant level (MCL) for microbiological contaminants and  is based on the presence or absence of total coliforms in a sample. The rule is applicable to public water system so as to determine compliance with the MCL for total coliforms in every  month in which it is monitored. Systems, which collect at least 40 samples a month, are in compliance if no more than 5.0 percent of the samples collected during a month are total coliform-positive. Systems, which collect fewer than 40 samples a month, are in compliance if no more than one sample collected during a month is total coliform-positive. Any coliform-positive repeat (check) sample following an E. Coli or fecal coliform-positive routine sample constitutes an Acute MCL violation. Public notices are required to be provided to customers. When the sample test shows total coliform-positive, the sample is subsequently analyzed for E. Coli or fecal coliform .Repeat samples are subsequently collected within 24 hours of learning of the positive result. In case one or more of the repeat samples are total coliform-positive, the system collects additional set of repeat samples in the same manner as the first set.

 

Figure 2:Total samples analysed for bacteriological content during August to December

 

Total coliform counts are determined in these samples. Samples with Total coliform count greater than 16 are considered as “Unfit” for drinking purpose. Results of zone wise Tap water samples analysis is summarized in Table 3. It is observed that Zone Nos 7, 9, 10 indicated the maximum “Unfit” samples. These zones has greater than 5 percent of the samples testing total coliform positive when compared to zones 2, 3, 4and 8.  Samples found unfit from various zones were subjected to further analysis to identify Thermotolerent positive bacteria. Figure 3 summarizes the results of Thermotolerent bacteria analysis for samples from various zones over a period of 4 months viz. August to December. It is observed that Zone 7 had the maximum positive samples during month of August, followed by Zones 2, 6 and 4. Thermotolerent analysis also acts as indicator for confirming the contamination of potable water supply lines. The supply line needs cleaning, swabbing and detection of leaks in water distribution system. During pre and monsoon season. Steps are needed for preventive maintenance of treatment plants and providing proper chlorination dose at the plants as well as at the ESR.

 

Whenever such contamination is observed, immediate instructions are issued to the authorities in these Zones to check the chlorination dose at the Elevated Supply Reservoirs. Simultaneously, repeat samples are collected from the same end location in the second round of sampling to see the effectiveness of chlorination at the ESRs. It is observed that except Zone No.1 and 6, all other zones still persisted in providing “Unfit” samples.Out of 10 zones studied 8 zones tested positive for total coliform count and exceeded the MCL criteria set by EPA. Zone 7 indicated the maximum number of “Unfit “samples.In the repeat round after chlorination at the distribution reservoirs the total coliform count exceeded the MCL for six zones. A third repeat round of sampling was desirable to improve the chlorination and reduce the contamination at the tail end locations. The results of third round analysis are summarized in Table 3 water quality in most of the Zones had improved resulting in only three zones exceeding the TCR limit. The authorities in these zones were informed to look into the problem of contamination The supply lines needed cleaning, swabbing and detection of leaks if any, in the distribution system The results of “Unfit” sample analysis are also illustrated in Figure 4.

 

The above surveillance study clearly indicates that there is a substantial improvement in water quality in the distribution system which confirms with the observation of  Health Department of Nagpur Municipal Corporation  that the cases of Gastroenteritis in the city has reduced from 786 in 2007 to 157 in 2008 ( Figure 5.). 

 

Figure 3: Total number of samples found Thermotolerant positive during August to December in various zones of the city

 

Figure 4: Total number of samples found unfit during August to December in various zones of the city

 

TABLE3: Zone wise analysis of samples

Sr No.

Zone

No.

Source

1st Round (Routine)

2nd Round(Repeat)

3rd Round(Repeat)

Total

Samples

Unfit

Compliance with TCR

%

Total

Samples

Unfit

Compliance with TCR

%

Total

Samples

Unfit

Compliance with TCR

%

1

1

Tap

530

6

1.13

6

0

0

-

-

-

2

2

Tap

530

41

7.73

41

3

7.32

3

0

0

3

3

Tap

530

35

6.60

35

3

  8.57

3

0

0

4

4

Tap

535

33

6.17

33

11

33.33

13

1

7.69

5

5

Tap

540

46

8.51

46

15

 32.60

15

3

20.00

6

6

Tap

530

25

4.71

25

0

    0

-

-

-

7

7

Tap

540

114

21.11

114

50

43.85

50

23

 46.00

8

8

Tap

540

40

7.40

40

2

5.00

2

0

0

9

9

Tap

540

90

16.66

90

2

2.22

2

0

0

10

10

Tap

530

90

16.98

90

8

8.88

8

0

0

* Unfit : samples with Total Coliform >16

Figures in Bold indicate violation of MCL

 

Figure 5: Gastroenteritis cases in Nagpur city during 2007 and 2008

 

Growth of microorganisms in the distribution system:

Although water treatment processes are capable of reducing heterotrophic microorganisms, still the  waters from most treatment plants typically contain higher numbers of microorganisms. Some viable organisms remaining in the water gets multiplied if nutrients are available, especially in waters that are above 15°C, and may lead to the formation of biofilms on internal surfaces. Biofilms typically contain numerous free-living heterotrophic bacteria, fungi, protozoa, nematodes and crustaceans. Older units in the treatment plants may contain deposits and sediments formed by the internal corrosion of metal pipes. They may also contain many microorganisms. The multiplication of bacteria in a piped distribution system is due to the availability of organic and inorganic nutrients in the conveyed water and in surface deposits.

 

Households and large building systems:

Water usage, pipe materials and water-purification devices (point-of-use or point-of-entry) can positively or negatively affect water quality in buildings. Water in household or building pipes can stagnate for long periods, leading to deterioration in the microbial and chemical quality of the water. Buildings at risk include schools during a vacation period, hotels with intermittent room occupancy, large buildings relatively unoccupied during weekends and sections of hospitals closed for long periods. These situations require planning from responsible authorities to ensure public health protection.

 

Factors contributing to contamination of water:

·         Intermittent supply of water through distribution system containing corroded pipes, leaky joints, defective house connections. The stagnant water enters the water mains through leaky joints during non- supply hours.

·         Bad workmanship of service connections. This includes illegal connections of   inferior  quality.

·         Defects developed in joints during or after deep excavations by other utilities such as  digging of telephone cables in the neighborhood area.

·         Abandoned service pipes

·         Improper location of Water Mains and House connections passing through      nallah/sewer/ storm water mains

·         High water table where pipelines always remain submerged in water

 

Preventive Measures:

Some of the preventive measures that can be considered for avoiding contamination are ;

·         In intermittent water supply system, the water mains may be charged  for 24 hours       with low pressures till the contamination are removed

·         Proper maintenance of  water supply system

·         Proper maintenance of sewerage and storm water system

·         Replacement of old /corroded water mains

·         Replacing corroded /leaky/defective service pipes and fittings

·         Cutting of disused communication pipes on ferrules on water mains

·         Physical disconnection of abandoned water distribution network of PVC/ Corroded GI Pipes pipeline in conservancy lanes

·         Protection of wells from contamination by coliforms by appropriate placement and  construction;

·         Maintenance of a disinfectant residual throughout the distribution system;

·         Proper maintenance of the distribution system including appropriate pipe replacement     and repair procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, and continual maintenance of positive water pressure in all parts of the distribution system;

·         Filtration and disinfection of surface water, and disinfection of ground water using strong oxidants such as chlorine, chlorine dioxide," [or chloramine];

 

CONCLUSION:

The study has indicated that bacterial contamination of drinking water is a major   problem in urban water supply and distribution system. Regular monitoring of raw water and treated water is the only way to evaluate whether bacteria is present in a water supply system.  With the steady increase in the population of the city and rapid expansion of various schemes and infrastructure activities in the region, the demand of water consumption is going to increase.. The pace of water supply does not commensurate with the water demand of the population. This has resulted in increased load on the existing water distribution systems resulting in reduction in water pressure in various parts of the city.  and more steps are needed to stop water loss due to leakage in pipe lines.

 

Proper pipelines and chlorination at the source end are keys to avoiding bacterial contamination of drinking water. If contamination is present, attempt must be made to identify and eliminate the source of the contamination. During pre and monsoon season, steps are needed for preventive maintenance of treatment plants and ESRs.

 

The study has led to development of monitoring network of determining the quality of water in an urban supply system. There should be no change in the quality of treated water from the time it leaves the treatment plant until the time it is consumed. However, in reality substantial changes do occur to finished water because of complex physical, chemical, and biological reactions. It is essential that such monitoring be carried out on routine basis, to provide the consumer safe water for drinking

 

ACKNOWLEDGEMENTS:

The authors are thankful to all staff of Anacon Labs for their cooperation and useful discussions.

 

REFERENCES:

[1]   AWWA (1999). Water quality and treatment. A handbook of community water supplies, 5th ed. McGraw Hill Inc, New York

[2]   WHO (2003).Heterotrophic plate counts and drinking water safety: the significance of HPC’s for water quality and human health. Eds.Bartram  J, Cotruvo J, Exner M, Fricker C, Glasmacher A. World Health Organization, Geneva, IWA Publishing.

[3]   Sobsey MD (1989). Inactivation of health related microorganisms in water by disinfection processes. Water Science and Technology, 21(3):179-195.

[4]   Craun GF, Berger PS, Calderon RL (1997). Coliform bacteria and waterborne disease outbreaks. Journal of the American Water Works Association. 89(3):96-104.

[5]   IS (1991), “Indian Standard Specifications for Drinking Water: IS:10500”, Indian Standards Institute, New Delhi.

[6]   IS 1622 (1981) Indian Standard Method of Sampling and Microbiological Examination of water, First revision 2003

[7]   IS 3025 (Part 26) (1986).Indian Standard  Method of Sampling and Test (Physical  and Chemical ) for water and Wastewater , Chlorine Residual

[8]   EPA Total coliform Rule (TCR) (1989) 54 FR 27544-27568, June 29,Vol. 54, No. 1241.

 

 

 

 

 

Received on 17.02.2013         Modified on 20.04.2013

Accepted on 25.05.2013         © AJRC All right reserved

Asian J. Research Chem 7(1):  January 2014; Page  11-18