FATE OF A FEW INDICATOR MICROORGANISMS IN TWO TREATMENT PLANTS : A CASE STUDY

Abstract

Contaminaied water caused by the poor sanitation can lead to both waterborne and water-contact diseases. Water born diseases are those acquired by injection of pathogens not only through drinking water, but also from water that indirectly into a person's mouth through washing food, utensils and hands. Generally, studies carried out on a municipal wastewater treatment system pay more emphasis on the removal of BOD and SS and on removal of pathogenic microorganisms. The aim of the present project was to study the die off of some of the indicator organism at different stages of the two treatment plants namely (1),18 MLD activated sludge process, and (2),a 6 MLD oxidation pond system. Water and wastewater samples were collected from different stages of ASP at Kankhal; oxidation pond system at Lakkarghat, and from river upstream & downstream of wastewater discharge from ASP Kankhal. All the samples were analyzed for total coliforms, fecal coliforms, and fecal streptococci on different dates. The average TC, FS, and FC concentrations in the raw wastewater from Hardwar city were found to be 36310000, 2214333, and 10176667 per 100m1. These values were reduced by 53.24%, 54.04%, and 56.46% respectively during primary treatment of wastewater and by 99.70%, 99.63%, and 99.79% respectively when both primary and secondary treatments were provided. Finally treated effluent from ASP contained 22x103 FC/100m1 exceeded limit of 1000FC/100m1 recommended by WHO for unrestricted irrigation. At STP, Kankhal mixing of X10 MLD untreated wastewater with r,-.20 MLD treated wastewater results in substantial increase of TC, FS, and FC values in the effluent to be discharged into river Ganga. Discharge of mixed wastewater into the river resulted in increase of TC, FS, and FC concentrations from 16, 76, and <3 per100m1 to 1101667, 121433, and 225000 per 100m1. Hi Upgradation of STP for increased flows along with provision of disinfection facilities for total capacity is must The average TC, FS, and FC concentration in raw wastewater from Rishikesh city were found to be 25250000, 4500000, and 13650000 per 100m1. There will total five oxidation ponds in series and overall removals were found to be 99.98%, 99.97%, and 99.99%. TC, FS, and FC concentrations in treated effluents were found to be less in case of oxidation pond system compared to ASP. However, even treated wastewater from oxidation pond system contained TC, FS, and FC concentrations higher than WHO prescribed limits. Disinfection is required as wastewater used for irrigation purposes and comes in human contact when discharged in river Ganga. Ratio of FC/FS was found to be greater than 4.0 for Hardwar city wastewater indicating dominance of human wastewater in raw domestic sewage.