A case study — “ How an operational guide lines with proper utilisation of sources of water & regular monitoring , can help to meet up the domestic demand and also to improve the quality for water uses in one of the housing complexes ” in Kolkata
It is a fact that there are some impeding factors which are to face by some of the housing complexes to meet up the need for daily domestic water uses in the supply system. However, by following some operational guide lines with proper utilization of the existing sources of water within the available scope and also keeping regular monitoring in the system, perhaps, it may be possible to improve the overall water management reasonably .
The instant complex for discussion , is comprised of 8 blocks with (G+4) storey buildings and along with 116 flats.
There is underground reservoir with the capacity of 1, 50,000 litres and also having 8 overhead tanks on top floor of each Block, with most of them bearing capacity of 8000 litres.
The complex comprise of 8 Nos. Overhead Tanks at 8 Blocks:- they are i) Tank (A) : Main Supply Reservoir- Capacity of 8000 Litres
ii) Tank (B) : — Capacity of 8000 Litres
iii) Tank ( C) : — Capacity of 8000 Litres
iv) Tank (D) : — Capacity of 8000 Litres
v) Tank ( E) : — Capacity of 8000 Litres
vi) Tank ( F) : — Capacity of 8000 Litres
vii) Tank ( G) : — Capacity of 17,000 Litres
viii) Tank ( H) : — Capacity of 8000 Litres
The Distribution pipe lines / net works. :
Out of 2 Delivery connecting Pipelines, one Pipeline joins the Overhead Tanks from:- block “A” to “F”.
The other connecting Delivery Pipeline joins the Overhead Tanks from: — block “A “ to “G” to “H”
Source of Water Supply:
i) Surface Water : varying from 20,000Lit to 40,000 Litres (approx.) from KMC system through 2 Ferrules.
ii) Bore-well Water : 80,000 Litres to 1,00,000 litres (approx.)
The underground reservoir receives KMC surface water via two number ferrules and later supplies on the overhead tank, lifted initially at the block “A”, through a pipe line.
At the same time, the bore well water too, is also can be received directly at the overhead tank located at the block “A” through a separate vertical pipe line and subsequently, connected with other over head tanks at different blocks to maintain the supply system.
The bore well water is also received in the main underground reservoir for initial storage through connecting pipe line, where an attempt has been made for initial blending of two sources of water like KMC and bore well water.
Apart that , the over head storage pumps located at different blocks are inter connected to receive water from the storage tank at “ A” which is joined with two separate intake system.
One pipe line is connected from underground reservoir and other pipe line is connected from Bore well pump system. Both are ending at overhead tank at “A”.
Here, it is pertinent to mention that to maintain the smooth flow of water into the distribution pipe line , it is essential to see that there remains some specific head difference always amongst the overhead tanks and If any short fall in head of water level , is detected which prevents the flow into the next successive tank , to combat the situation it has been kept reserved with two stand by Tulu pumps to create forced flow to the delivery line .
Now, to confirm the flow quantity, as per scheduled quantity , at present , one flow measuring unit had been installed at the outlet point of bore well pump & it is seen from the available record that the consumption of bore well water (on an average) is around 1, 00,000 litres per day. Even, some days, perhaps, it goes beyond that may be around 1, 15,000 litres.
It is also understood that while the Bore well pump is operated for 10 hours, the drawal of total water in a day is likely to be 99,600 litres which appears to be in conformity with the flow measuring data.
It appears also that at the moment the consumption of KMC surface water , likely may be within the limit of 20,000 litres to 40,000 litres per day ( approx.).
Now, in the present background , it is also felt that instead of catering water separately to the overhead tank at “A “ from the two sources i.e. i) KMC water in the underground reservoir & ii) the bore well water , it needs to be blended in the underground reservoir itself prior to lift at the tank “A” .
At the moment, the percentage of ground water consumption is around 70 % 80 % and even more. More uses of water, results more withdrawal of bore well water, increasing further its percentage with respect to overall consumption.
With the above facts and also taking into consideration of all the constrained parameters and boundary conditions , it is felt that by following some specific operational guidelines and other related activities including regular maintenance, it may help to improve & meet up , both the quality and quantity of domestic water at the instant complex.
However, it still requires some more steps and measure, which is to be implemented according to need based demand.
One thing it is very much important to see the overall consumption of domestic water should not exceed beyond the quantity of 1, 00,000 litres per day in the complex. ( i.e. if we consider 165 litres per day per person , at the receiving end as per prevailing KMC guide line , total consumption will likely be 165 x 116 x 5 = 95,700 litres , say 1,00,000 litres ) and out of that , the consumption of bore well water in the complex, should remain within the quantity 80,000 litres ( maxim.) and also needs to be reduced further in phased manner.
Now, the residencies consume 1, 00,000 litres per day of ground water on an average , as understood from the recorded data of the installed flow measuring unit, at the off take point of bore well pump.
Similarly, to identify the actual quantity of KMC surface water , one more flow measuring unit also needs to be installed at the intake take point of its delivery pipe line, which is likely to be 40,000 litres with the existing arrangement of 2 numbers of ferrules.
Such identification of the actual quantities pertaining to two different water sources i.e. KMC surface water & raw bore well water , may help a lot to guide the blending process with a intention to improve the quality pertaining to TDS parameter is concerned. .
Therefore, with the existing conditions and also taking into account other related constraint factors, the operational guideline has been framed up to see that the overall water is consumed within the limit of 1,00,000 lit, out of that the use of bore wall needs to be restricted within 80,000 lit ( max), preferably to be further less for maintaining the water quality reasonably acceptable in the Water Supply system at the instant complex.
The Facility Manager (FM office) of the complex should meticulously follow the operational guideline and keep record all the relevant data in the proper register.
This is very important, both for monitoring and future evolving process to improve the efficacy of the water supply system including the quality at the complex, befitting our requirement.
It may be reiterated that at the moment about 70% to 80% of bore well water is mixed up with the KMC surface water in the underground reservoir.
It is seen that the bore well water does not provide portable drinking water and also due to high presence of Iron and TDS parameter in the underground water , it is also not compatible for domestic use .
It is to mention over here that as per test report, it is observed that all the parameters of Bore well water in the instant complex i.e Turbidity, TDS, Total Hardness, Calcium, Magnesium, Total Alkanity , Chloride and Total iron etc. are above the acceptable limit of IS10500–2012 (second revision ) as codified for the Drinking Water Specification .
Though, in the instant complex, one attempt has been made to improve total iron parameter by installing an Iron Removal System , the results appear to be not in consistent with that of the acceptable limit of IS10500–2012, thus, it needs to be monitored and kept under maintenance regularly.
Now , if the raw bore well water is blended with the KMC surface water particularly which is being supplied from GRWTP , the TDS is likely to be reduced significantly as the TDS of KMC surface water , remain probably within 150mg/lit to 250 mg /lit. , therefore, the attempt should be — to see that more & more , surface water is used to blend with the raw bore well water, that to help improving the quality of water accordingly.
Moreover, we also understand that each flat has R.O Purifier, which can reduce the TDS of blended water, ( which varies within the maximum limit of 700 mg /lit ) down to the tune of 100 mg/ lit or so .
Thus, we may see the possibility to increase the intake of surface water from KMC system in phased manner commensurate with the actual demand in future and of course, provided, it is made available at the particular locality. At present, in the instant complex, the surface water contributes only 30 % (maximum).This may be one approach to improve the existing quality of water.
Our main intention is to find out the ways and means to enhance the contribution of sweet water ( KMC surface water ) to the maximum extent, out of total requirement of domestic water , of course , negotiating the permissible cost factor , affordable to the residencies of the complex.
It is pertinent to mention that the current fee structure for water consumption through Bulk Meter is: Rs. 7/- per kilo-litre for domestic purpose.
Apart that, sometimes it has been also experienced that in case of shut down of bore well pump , it requires to receive KMC tank water for temporary water storage in the underground reservoir to combat emergent need , for which it needs to be paid to KMC authority — Rs 450 for each tanker with a capacity of 3600 lit . i.e at the cost of Rs 125 per kilo-litre.
Along with, it should be seen that the work of cleaning and disinfection of overhead and underground reservoirs as well as the flushing & distribution of pipelines at certain interval of time is continued ( preferably once in a month ) at each of the eight block. This will help to remove algae, mud, sludge, dirt including bacteria and other micro organisms etc. from inside walls and the bottom surface of both the roof and underground tanks. The cleaning of deposited materials in the distribution pipe lines will also improve flowing condition and save electricity bill and pressure in electric motor system.
Apart that, care need to be taken for regular recording the flow data in the proper register , observed in the water flow measuring units to assess the quantum of water for — “ both raw bore well water and KMC surface water” , so that it can help in regulating the quality & quantity through blending process to the maximum extent within the existing available scope .
Finally, I like to highlight some of the basic feature of important water parameters those are linked with the problems of domestic water.
i) Hardness is expressed in terms of calcium carbonate (CaC03).
Actually, “Hard water” brings some basic drawback, which include grey staining of washed clothes, scum on wash and bath water following use of soap or detergent reduced lathering of soaps, build-up of scale on electric heating elements and boilers reduced water flow in hot water distribution pipes due to scale build up accumulation of whitish-grey scale in tea kettles and other containers used to boil water
It may be stated here that Water with less than 75 milligrams per litre (mg/l) is considered soft, 76–150 mg/l moderately hard, and above 150 mg/l, hard water.
ii)Total Dissolved Solids (TDS) :
The total dissolved solids test measures the amount of particles that are dissolved in the water. It may include all suspended solids that may or may not pass through a filter.
Dissolved solids” refer to any minerals, salts, metals, cations or anions dissolved in water. This includes anything present in water other than the pure water (H20) molecule and suspended solids. In general, the total dissolved solids concentration is the sum of the cations (positively charged) and anions (negatively charged) ions in the water, expressed in Parts per Million (ppm) is the weight-to-weight ratio of any ion to water
Drinking water may have a TDS reading of 25–250 mg/L., Drinking water should not exceed 500 mg/l ( TDS), where as Distilled water will have a TDS reading that will range from 0.5–1.5 mg/L.
The amount of TDS ranges from 100–20,000 mg/L in rivers and may be higher in groundwater, Seawater may contain 35, 000 mg/L of TDS.. Lakes and streams may have a TDS reading of 50–250 mg/L.
iii) Total Iron:
In drinking-water supplies, iron (II) salts are unstable and are precipitated as insoluble iron (III) hydroxide, which settles out as a rust-coloured silt. Anaerobic groundwater may contain iron (II) at concentrations of up to several milligrams per litre without discoloration or turbidity in the water when directly pumped from a well, although turbidity and colour may develop in piped systems at iron levels above 0.05–0.1 mg/litre. Staining of laundry and plumbing may occur at concentrations above 0.3 mg/litre.
Iron also promotes undesirable bacterial growth (“iron bacteria”) within a waterworks and distribution system, resulting in the deposition of a slimy coating on the piping.
As per IS 10500–20 12, total Iron should be : < o.3 ppm as Fe, it may be stated that no relaxation of the Iron content in the upper limit is allowed beyond 0.30 mg/l. Therefore, if it is found in the test report that the raw water contains “ Iron “ which is reasonably higher against 0.30mg/l , it may be required to install an I.R plant for filtering through Iron removal Filter to ensure its improvement to keep it within the maximum limit of < o.3 ppm,
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.
It can block light to aquatic plants, smother aquatic organisms, and carry contaminants and pathogens, such as lead, mercury, and bacteria.. Turbidity is measured in NTU. The allowable limit (A.L) of 1.0 NTU
v) CHLORIDE :
Chloride is present in all natural waters, mostly at low concentrations. It is highly soluble in water and moves freely with water through soil and rock. In ground water the chloride content is mostly below 250 mg/l except in cases where inland salinity is prevalent and in coastal areas.
Chlorides are widely distributed in nature as salts of sodium (NaCl), potassium (KCl), and calcium (CaCl2). Chloride is not toxic to human health at low levels but does pose taste and odour issues at concentrations exceeding 250 mg/l. to contamination.
BIS (Bureau of Indian Standard) have recommended a desirable limit of 250 mg /l of chloride in drinking water, this concentration limit can be extended to 1000 mg/l of chloride in case no alternative source of water with desirable concentration is available. However ground water having concentration of chloride more than 1000 mg /l are not suitable for drinking purposes.
Sodium in drinking water is a health concern for individuals restricted to low-sodium diets due to hypertension (high blood pressure). Therefore, contamination of Sodium to any concentration above 20 mg sodium per litre of water (20mg/l), need to be monitored .
Sodium chloride , is composed of 40 percent sodium ions (Na +) and 60 percent chloride ions (cl-) . Water contaminated with NaCl creates a higher water density and will settle at the deepest part of the water body where current velocities are low such as in ponds and lakes.. This leads to the bottom layer of the water body becoming void of oxygen and unable to support aquatic life.
vii) E- Coli form organisms:
Ideally, all samples taken from the distribution system including consumers’ premises should be free from coliform organisms. In practice, this is not always attainable, and the following standard for water collected in the distribution system is therefore recommended when tested in accordance with IS 1622: 1981.
a) Throughout any year, 95 percent of samples should not contain any coliform organisms in 100 ml;
b) No sample should contain E. Coli in 100 ml;
c) No sample should contain more than 10 coliform organisms per 100 ml; and
d) Coliform organisms should not be detectable in 100 ml of any two consecutive samples.
If any coliform organisms are found ,the minimum action required is immediate resampling. The repeated finding of 1 to 10 coliform organisms is 100 ml or the appearance of higher numbers in individual samples suggests that undesirable material is gaining access to the water and measures should at once be taken to discover and remove the source of the pollution.
The standard prescribes the requirements for the essential and desirable characteristics required to be tested for ascertaining the suitability of water for drinking purpose.
Everything possible needs to be done to prevent pollution of the water.
i) Obvious sources of contamination should be removed, special attention being given to the safe disposal of excrement.
ii) Untreated sources of water, like Bore wells, normal Wells and storage tanks etc should be protected by all means to stop contamination in any form.
iii) Access of man and animals should be restricted by fencing, and should be so designed that fouling is prevented when drawing water.
iv) Moreover, if not supplied through pipes, water from such sources is likely to undergo further deterioration in quality during transport or storage before drinking. Containers used for water should be kept clean, covered and clear of the floor.
v) The most important factor in achieving these objectives is to ensure the cooperation of the local community, and the importance of education in simple sanitary hygiene should be strongly stressed.
According to the study, the Centre’s decision to keep the arsenic level in water at 50 µg/L was “rather relaxed”, as the same for WHO is 10 µg/L.
“Hundred wards out of 144 have alarming level of arsenic contamination in their unconfined shallow water table, of the 100 infected wards, 51 (35.4 per cent) have arsenic level above 50 µg/L, while the level in the rest is between 11 to 50 µg/L ,only 30 per cent of wards (44) across the city have arsenic levels below 10 µg/L…” the report said.
The arsenic contamination threat in Kolkata has changed alarmingly since 2009, said a study published in the Environmental Monitoring and Assessment journal on September.
The wards under arsenic contamination threat have increased in number, and the situation in most parts of Kolkata has become seriously alarming,” the study said, adding that this increase in contamination isn’t just related to the increase in population, but also dependent on the “lack of groundwater replenishment in certain regions”.