Physico-chemical and Microbiological Studies for the Underground Water of East Dwarka Subcity of Delhi and the Impact of Rainwater Harvesting on its Quality

Earlier work has suggested that with the increase in the consumption of water due to the growing population of Delhi, there is a continuous decrease in the water level in the parts of Delhi. Due to this decline water is getting saline which is making it harmful for vegetation; also its taste is being affected. To overcome such problems rainwater harvesting systems have been established. Rainwater harvesting dilutes the dissolved salts in ground water. In the present study water samples, from various societies of Dwarka subcity of New Delhi have been collected where rainwater harvesting systems are installed. The impact of rainwater harvesting on the quality of ground water has been studied by collecting water samples from these selected sites in the months before after and during the rain. The present study revealed that the rainwater harvesting suitably affected the quality of ground water.

increases the water level.In this regard, we have determined the physico-chemical and microbiological parameters for the underground water samples collected from the various societies of the said sub city where rainwater-harvesting systems are installed.The parameters have been determined before and after the monsoon.On the basis of the data available, it has been concluded that rainwater harvesting can solve the problems related to water.In such harvesting systems the rainwater-harvesting pit designed specially is connected to the drainage network.Through this network water is stored directly in underground aquifer layers to increase the ground water potential.

Reagents and Instruments
The main reagents used for the analysis of water samples were obtained from CDH, GHC, E-Merk, Qualigens (India).All other reagents and chemicals were of analytical reagent grade.A digital pH meter ( Elico LI-10, India), a UV/VIS spectrophotometer (Elico EI 301E, India), a B.O.D. incubator, a water bath and a incubator shaker.All these instruments were used to determine the physico-chemical parameters

Collection of water samples
Each fifteen ground water samples were collected on 1 st day of May 2004, 1 st day of July 2004, 1 st day of August 2004, 1 st day January 2005 & l st day of March 2005.All samples were tightly sealed and immediately taken to the laboratory for analysis.During the analysis all samples were stored in dark and cool environment (at 4C° approx.)

Sampling sites
Ground water samples collected from fifteen societies where rainwater-harvesting systems are installed.The names of the societies are as follows.

Data Analysis
All Physico chemical and microbiological parameters determined for the abovementioned samples, have been listed in tables 1-6.The physicochemical parameters are, Alkalinity determined by acid titration 3 , Hardness determined by the complexometric titration method 3 , Chloride ions determined by Argentometric method (Mohr's Method) 3 , Dissolved oxygen determined by the Winkler's Method 3 as well as NO determined by UV/VIS spectrophotometer 3 .The coliform determination is done using Mackonkey broth as a media for the grouth of coliform.

RESULTS AND DISCUSSION
Physico-chemical and microbiological studies of underground water of eastern part of Dwarka subcity of New Delhi {Fig 7(a) & 1(b)} were performed in all the three seasons of year 2004 & 2005.For the present studies water samples from fifteen different stations were collected in May, July & August of year 2004 as well as January & March of Year 2005.These months were selected in a view to assess the quality of under ground water before monsoon, during monsoon and after monsoon.All the stations selected for collecting the water samples were provided with rainwater harvesting pits to study the effect of rainwater harvesting on the quality of under ground water.The results for all the determined parameters of the present study are listed in table 1 (befor monsoon) table 2 & 3 (during monsoon) and table 4 & 5 (after monsoon).The same parameters were also studied for the rainwater and listed in table 6.
It was found that the values of almost all the parameters for the water samples of all the fifteen sampling stations (collected before and after monsoon) are within the maximum desirable limits of the drinking water specifications (IS 10500:1991 & WHO).The pH values for all the studied samples collected before rain i.e.May 2004 are ranging from 6.7 to 8.2.However, these values for almost all the samples collected during monsoon, were slightly decreased due to harvesting of rainwater (pH=6.5).] for all the samples collected in May 2004 is below 500mg/L, which is desirable for drinking water.For all the samples collected before the monsoon, the determined values for chloride ions (Cl -) were ranging from 120 mg/L to 560.92 mg/L, for sulphate ions (SO4 -) from 23.1 mg/L to 144 mg/L and for alkalinity from 285 mg/L to 611.6 mg/L.(Table 1).For all the above parameters the values are well within the permissible limit of the drinking water.The amounts of Nitrate (NO3 -) and Nitrite ions (NO2 -) present in all the samples collected in May 2004 were sufficiently below the permissible limit of drinking water.All the above-mentioned parameters were Dissolved oxygen contents for all the studied water samples were found very from 7mg/ L to 9mg/L, which were almost unaffected by rainwater harvesting.Very low values of BOD ranging from 0.00 to 1.60 mg/L for all the studied samples collected before and after harvesting indicate that all these water samples were free from microorganism as well as organic pollutants and are therefore safe for drinking.

Variation in pH is shown in figures [
It was found that for all the fifteen water samples collected before monsoon the coliform count was ranging from 00 to 4 coliform colony / 100 ml which is quite less than the permissible limit (<10 coliform colony/100 ml).However the number of coliform organism were detected more in few water samples (8 to 12 coliform colony /100ml) collected during monsoon but these numbers as per Bureau of Indian standard specification & WHO for drinking water were below the permissible limit except the numbers of one sample i.e. 12 coliform colony /100ml.The reason for more number of coliform present in the underground water during monsoon is attributed to the contamination of rainwater by the atmospheric organic pollutants and microorganism.

Conclusion
The physico-chemical studies, which have been performed for various samples of water collected before and after monsoon, show that the hardness, alkalinity, T.D.S, NO 3 -, NO 2 -SO 4 2-and Cl - of almost all the samples have been decreased appreciably due to the mixing of rain water to the under ground water.Thus, indicative parameters e.g.pH, T.D.S., alkalinity, etc. performed before and after monsoon indicate that rainwater harvesting suitably affects the quality of ground water.And rainwater harvesting has proved its utility for the abovementioned sites.
Fig 1(a) & 1(b)].As regards, TDS [Fig 2(a)&(b)] the values for the samples collected before rains were found to be ranging from 333.2 mg/L to 1011.9 mg/L .All the values are within the permissible limit.A decrease in the TDS values for all the samples collected during monsoon was observed.The observed values of