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Research Paper & Presentation
 
Case study
Baramati (Dist. Pune) Maharashtra (Trouble Shooting)
 
Introduction :
A part of Baramati town (Dist.Pune, Maharashtra, India) receives their drinking water supply from Ujani reservoir. This plant of 5.0 mld capacity was constructed by Maharashtra Jeevan Pradhikaran (M.J.P.) The reservoir is located on the downstream side of Pune town. It receives fairly polluted water due to mixing up of partially treated sewage, industrial waste and farmland runoffs. The jack well which supplies the raw water is located in the backwaters of dam. It pumps raw water to a five m.l.d. (million liters/day) water treatment plant located on a hillock, the treated water is supplied to the town by gravity. The treatment consists of aeration, flocculation, tube settling , gravity sand filtration and chlorination. The plant was operated only intermittently for 10-12 hours per day.
In summer of 2006, the citizens complained of yellow-brown tinged, smelly tap water. On investigation , it was found that raw water contained blue-green algae and iron. The raw water had greenish-black tinge and had smell of putrefied fish. The plant walls had turned black. Calcium hypochlorite (Bleaching Powder, CaOCL) which was used for pre-chlorination had very little available chlorine. Since the plant received only intermittent electrical supply, many a times flocculators were not operated. Hence tube settling tank had become ineffective to remove algae and iron. After filtration, the color and residual chlorine were not observed, but again after post chlorination with bleaching powder yellowish-brown tinge appeared to the water (Excessive Ph re-dissolves iron as per the literature) . Bleaching powder dosing was replaced by chlorine gas. Alum was replaced by poly-aluminium chloride. Diesel generators were procured to run flocculators continuously. This mitigated the problem to some extent but not completely . As per AWWRF recommendation the intact cells of algae were tried take out of the system (flocculation-settling), pre-chlorination dose was in fact reduced not bring out the intracellular matter from cells. On peripheral investigation, it was observed that raw water quality received by an another plant on same source was much better. Investigation focused on the Jack well. Since the jack well was submerged in lake water, help was sought from the local authorities for investigation. Divers found out that there were three inlet ports at different levels. Only bottom-most inlet port of the well was open and was drawing the water. Water samples from the surface of lake revealed that the water quality was much better at the surface (compared to which was being pumped at the plant). As a remedial measure, Immediate efforts were made to close the bottom gate and open the upper-level gate. It was not simple, as the lack of maintenance had jammed the movement of gates. However, on performing this task, the raw water quality improved appreciably. The modified treatment with improved raw water quality, eliminated the residual color of treated water. Due to intense public pressure the investigators had initially concentrated on the plant operation. At the hind sight, lake eutrofication was found to be a main culprit and had resulted in layered waters having different water qualities. During the day the raw water quality also showed variations. The single most important factor in improving the treated water quality was change of inlet port of Jack well. During initial commissioning of the plant the inlet port selection had remained unattended.

Front view of Baramati Water Treatment Plant

Blue-green Algae

 

Iron and Calcium deposits on Cascade Aerator

Predominent algae and calcium sludge

 

Iron stains on Filter Outlet Chamber

Algae strained on filter paper

 
Photographs of Baramati Water Treatent PlantCourtesy : Maharashtra Jeevan Pradhikaran
 
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