Feasibility Studies on the Impact of Bioremediation Processes in Contaminated Urban Lake Environments

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1 Sengupta, M. and Dalwani, R. (Editors) Proceedings of Taal2007: The 12 th World Lake Conference: Feasibility Studies on the Impact of Bioremediation Processes in Contaminated Urban Lake Environments N. Vasudevan, K. Hemalatha, D. Walther and K. Thanasekaran Centre for Environmental Studies, Anna University, Chennai ABSTRACT Increased urbanization, farming and even birds decrease the quality of our lakes and streams by increasing the level of nutrients, particularly nitrogen and phosphorus, in the water results in deterioration of water quality often termed eutrophication. This can cause poor water clarity; scum and foams; unpleasant odours; and algae. Better land management is one way to help improve or to stop our water bodies becoming eutrophic, but changes may take years to improve water quality. To help improve water quality in the short term, mechanical, chemical and biological methods have been used. The present study was conducted in restoring a urban lake namely the Koranattu lake situated 50 kms south of Chennai city. The pollution of the water body is due to the run-off from the upper land area, sewage and solid wastes from the surrounding habitations including resorts. The pollution load shows COD, BOD, nitrogen and phosphate. After assessing the amount of pollution in the lake and identifying the influx of organic and hydraulic loads in the field, a laboratory study was conducted to understand the feasibility for remediating the lake water under different lake zonations such as littoral, limnetic and profundal and benthic conditions with a microbial cocktail. As the improvement indicators, the organic carbon concentration and the major nutrients (nitrogen and phosphate) concentrations were studied. The BOD, COD, TKN and odour removal was better in all the zonal conditions in the presence of microbial cocktail. The study revealed that the remediation technology could improve the lake in the removal of organic and nutrients at a faster rate than the natural self purification processes. Keywords: Bioremediation, Effective microorganisms, Lake, Wastewater INTRODUCTION Lakes are inland bodies of freshwater ranging in size from less than one acre to several thousands of acres. Lakes can also be categorized on the basis of their richness of nutrients, which typically affects plant growth such as oligotrophic (low in nutrients), mesotrophic (average level of nutrients), eutrophic (enriched with nutrients) and hypertrophic (excessively enriched with nutrients). They are divided in four zones on the basis of depth and distance from the shore line (littoral, limnetic, profundal and benthic zones). Lake hydrology describes the water flow in and out of the lake and their interactions with the surrounding. Increasing urbanization and industrialization generate large volumes of wastewater and their inflow into the lake results in europhication. One of the techniques being employed in the ecological rehabilitation of polluted lakes is the application of effective microorganisms (EM). This consists of the use of beneficial microorganisms sourced from nature which has proven to be successful not only in farming and animal husbandry and also in the treatment of polluted soils and wastewater. In the present paper, the feasibility of employing effective microorganisms on the impact of bioremediation processes in a designated urban lake situated on the outskirts of Chennai has been studied. MATERIALS AND METHODS Location and description of Koranattu lake Mahabalipuram is picturesque little town located 50 km South from Chennai in the South of India. It is well known for its heritage buildings built by the Pallava kings and is one of the well known places for tourists of Coromandel Coast.

2 Koranattu lake is one of the storage structures located in the centre of Mahabalipuram, close to the most important shopping area. It receives stormwater and sewage from the adjacent residential areas and shopping streets, transported through stormwater drains, which finally enters into the lake from the Northwest. Due to the continuous inflow of untreated wastewater, the lake has become eutrophic and depilated. As the banks are completely occupied by either legal buildings or encroachments, the view of the waterbody remains almost unnoticed to the public. ASSESSMENT OF BASELINE INFORMATION Flow Analysis V-Notch Weirs are used to monitor discharge in small open channels. A specially designed V-notch weir installed within an open channel will increase the water level on the upstream side by partially blocking the discharge. The height of the upstream water level is a direct measure for the total discharge in the channel measured at least 0.5 m away from the actual weir. Each V-notch weir has a geometry, which is calibrated to exactly fit the channel shape and the expected amount of discharge. The water level can be measured manually using a tape measure or automatically using ultrasonic distance transducers. The V-notch was made in wood, which has been fixed inside and the construction of 9 thick brick wall plastered with waterproof cement. The bottom of V-notch is 0.15 m. The height of the V- notch from ground level was m. The bottom of V-notch is subtracted with height of the V-notch from the ground level (ie, 20.1 cm -15 cm = 5.1 cm) to get the actual flow height. The angle of V-notch is 90 o. The height of the V- notch has been designed in such a way that it cause no major back storage (or back logging) and it will overflow during heavy rainfall events. On three different days namely on 6 th, 21 st of September and 26 th October 2006, the wastewater flow has been assessed at V-notch weir, that is at Korranatu lake. The flow was measured at every one hour from 7:00 to 19:00 hours on both the days (ie. 6 th & 21 st of Sep, 2006) and from 5:00 to 23:00 hours on 26 th October The samples were collected for analysis at three different time intervals (8:00am, 12:00pm & 4:00pm). At 8:00 and 16:00 hours, COD alone was analysed, at 12:00 hour, parameters like ph, EC, DO, temp, TDS, TSS, Turbidity, TN, PO P, COD, BOD 5 were analyzed. The hourly flow rate was calculated by taking average on three days from 05:00 to 23:00 hours, from 24:00 to 4:00 hours the flow rates were extrapolated. The water level was measured manually with a fixed measuring tape. The height of the flow through the V-notch was measured. The height, flow was calculated using the following formula: Q = 1.35 hi 2.48 where, Q = discharge over weir, in m 3 /S hi = head on the weir, in m Load analysis The organic volumetric loading rate, defined as the amount of BOD or COD applied to the aeration tank volume per day, and in this case L (Q) (S o ) org = (V) (10 3 g/kg) Where, L org = Volumetric organic loading, Kg COD/m 3.d Q = influent wastewater flow rate, m 3.d S o = influent COD concentration, g/m 3 V = aeration tank volume, m 3 Table 1. List of analytical methods S.No. PARAMETER APHA METHOD 1. ph 4500-H + WTW (ph 320 / SET), Horiba Multi Probe 2. Temperature WTW Temperature Probe, Horiba Multi Probe 3. Electrical Conductivity 2510 WTW (Tetra Con 325), Horiba Multi Probe 4. Dissolved Oxygen (D.O) WTW (Oxi 330/SET), Horiba Multi Probe 5. Turbidity 2130 Nephelometric method 6. Chemical Oxygen Demand (COD) 5220 Open Reflux Titrimetric Method 7. Biochemical Oxygen Demand (BOD) day BOD test 8. Total Kjeldahl Nitrogen (TKN) 4500-Norg N org Macro Kjeldahl Method 9. Total and Faceal coliforms 9221 MPN Technique 10. Nitrate (NO 3 ) NO 3 Copper Cadmium Reduction Method 11. Nitrite (NO 2 ) NO 2 Spectrophotometry 12. Total Phosphorus 4500-P Stannous Chloride Method 13. Ammonia (NH 3 ) NH 3 Titrimetric Method 51

3 Physicochemical analysis The composite samples were collected from the lake and well-mixed and taken at 3-4 different locations in the same lake. Five liter Polyethylene (PE) cans for Pond water and one litre PE cans was used to collect the samples for physico-chemical parameters. Sterilized glass containers are used to collect samples for microbial analysis. The collected samples are preserved in dark at 4 C and transported to the laboratory as soon as possible and the sensitive parameters were analyzed immediately. Analysis for coliforms was started with in 24 hours of sample collection. The analytical methods adopted are listed in Table 1 according to the test methods given in Standard methods for the examination of water and wastewater (APHA, 2005). average COD concentration is multiplied with flow rate for every one hour. From the Figure 4, we can infer that the organic loading was found to be high at 10:00 hrs, of Kg/day, which might be due to the kitchen waste generated while cooking. Preparation and activation of EM For a water body of 5000 sq.m with 500 cu.m. (5 million liter) of water we used activated EM (EMa) at the rate of 1:5000, based on EMa activated at the rate of 1 liter EM for 50 liters of EMa liters EMa four times a month amounts to four thousand liters EMa per month which corresponds to 80 liters EM per month. Experimental Set-up According to the work schedule, the samples were collected from the defined area and brought to the laboratory where it is transferred to a large container and is allowed for settling. Then the samples were transferred equally into smaller containers based on the study. The volume of the samples to be transferred depends on the type of the study. Depending on the volume of the sample, the EMa is injected. Mineralization studies were conducted in closed reactors of 5L and 3 L capacity with necessary ports for injection of EMa and collection of gas. Gas was collected by water displacement method. RESULTS AND DISCUSSION Wastewater flow into lake The average hourly flow rate for Korranatu is shown in Figure 2. The peak flow was at 10:00 hours with average daily flow of 5.68 lit/sec. From the Figure 3, we can infer that even though the flow increases and then decreases, the COD concentration was found to be almost same for all the three hours. The COD concentration at 8:00, 12:00 and 16:00 hours is almost similar. Thus, the average COD concentration was taken from the three different timings. The average COD concentration is 274 mg/l. To calculate the organic load for the whole day, the Characteristics of Koranattu lake water In Korranatu lake, the BOD concentration was between 37 to 45 mg/l, which is also higher than the standard of 30 mg/l disposal and CPCB standards for best designated water use criteria (Class B: 3 mg/l). The COD concentration was as high as 252 mg/l and the results of Koranattu lake water analysis are given in Table.2 52

4 Table 2. Water quality analysis for Koranattu lake water. Location Korranatu lake Parameter Unit Parameter Unit Heavy metals ph (in-situ) As EC (in-situ) (μs/cm) Cd BDL DO (in-situ) Cr Temp. (in-situ) ( C) Cu TDS Fe TSS Hg NH 3 -N Ni BDL NO 2 -N <0.1 Pb NO 3 -N Zn TKN (as N) PO 3 4 P COD BOD 3 (27 C) Total coliforms MPN/100 ml 2* 10 5 Faecal Coliforms MPN/100ml 9* 10 4 Table 3 Comparative Bioremediation Effectiveness of different concentrations of EM. Parameter TKN Ammonia Nitrite Nitrate BOD COD Concn of EM Initial day 0.2 ml ml ml BDL After 4 days 0.2 ml 2.8 BDL ml 2.8 BDL ml 2.8 BDL 0.24 BDL Phosphate TKN value was up to 31 mg/l. The actual TDS in the pond water is about 825 mg/l. The DO was recorded up to 9.5mg/L indicating high level of pollution and toxicity in the pond by the entry of grey water in to the pond. This condition makes the pond water almost a sewage water quality. There is less amount of Phosphate of 1.4 mg/l in the pond water against the EPR standard of 5.0 mg/l. Nitrogen and Phosphate are both nutrients and can be considered as beneficiary for plants. For installing a biological treatment system, there are enough nutrients available in the water to support a biological treatment process. The total coliforms in the lake was 1.9 x 10 5 MPN/100 ml and faecal coliforms were 9.8 x 10 4 MPN/100 ml. which showed the poor quality of the water. Basic parameters like BOD and coliforms of Korranatu Lake indicates higher pollution load compared to the CPCB Best designated water use criteria standards. The amount of TKN and phosphates indicate the eutrophication of the lake as revealed by the presence of algal blooms. The amount of coliforms makes the water not suitable for bathing purposes if Best-Designated-Use criteria are applied. Optimization of EM concentration From the studies conducted with different concentrations of EM, it was observed that 0.8 ml/l showed appreciable reduction in BOD, COD and coliform reduction. Improvement in DO and clarity of water was observed during the study (Table 3). Mineralization of organic nutrients To understand the mineralization of the organic nutrients, the study was conducted for two weeks in a closed reactor with respective water/wastewaters and EMa. At the end of 14 th day, analysis of the effluent, solids and gas was carried out for the respective samples. 53

5 Table 4. Mineralization of organic nutrients during the bioremediation of Koranattu lake water. 0 Day After 2 weeks 0 Day After 2 weeks Control EM BOD COD TKN Ammonia Phosphate MLSS MLVSS Gas (ml) In the control reactor where the samples were not treated with EMa, reduction in COD was 54 % (37 mg/l), BOD 72 % (18 mg/l) and TKN was 25 % (5.6 mg/l). There was no change in the concentration of MLSS and MLVSS when compared to the initial day. Total dry weight of the biomass produced during the period is 10.9 mg in the reactor (4 L). The Gas production of 26 ml was observed (Table 4; Fig.5). Out of the 37 mg of COD, an amount of 10.9 mg of biomass and 26 ml of gas was produced. Studies with Koranattu lake water with 0.2 ml/l EMa in the reactor (4 L) showed a COD reduction of 64 % (70.2 mg/l), BOD reduction of 95 % (43 mg/l), TKN 45 % (14 mg/l) and ammonia 50 % (5.6 mg/l). Total dry weight of the biomass produced during the period is 40.3 mg in the reactor (4 L). The volume of gas produced was 37 ml. The MLSS concentration has increased from 160 mg/l to 180 mg/l. Out of the 70.2 mg of COD, an amount of 40.3 mg of biomass and 37 ml of gas was produced (Table 4; Fig.5). A overall reduction in BOD up to 97 % was achieved within 4 days of EM treatment. The concentration of BOD in the EM treated Koranattu lake water was below 3 mg/l after 8 days which corresponds to the Class B of best designated water use criteria of CPCB. Ammonia in the water was removed completely and reduction in organics and total nitrogen was observed. The clarity of the water has improved after EM treatment along with odour reduction. REFERENCE APHA (2005) Standard methods for the examination of waste and wastewater. American Public Health Association, Washington, D.C. Bauerfeld, B. (2005) Investigation and optimization of a decentralized wastewater treatment plant in Pondicherry, India. Ph.D. Thesis, University of Luneburg, pp 95 (Personal communication) Cpheeo (1999) Manual on water supply and treatment, Ministry of Urban Development, New Delhi. Metcalf and Eddy (2003) Wastewater Engineering, 4 th Ed, p 1819, Tata McGraw-Hill, New Delhi. Sasse, L. (1998) DEWATS-Decentralized wastewater treatment in developing countries, p. 159, Borda, New Delhi. 54