PERFORMANCE OF SEWAGE TREATMENT PLANT (HARDWAR) WITH RESPECT TO SALMONELLA AND FECAL COLIFORM

Abstract

The presence and control of human pathogens in wastewater from community has emerged as a public health policy issue that impacts management practices of sewage treatment plants. This work mainly focuses on quantifying the reduction of pathogens (salmonella) along with indicator microorganisms (total coliform and fecal coliform), because generally, studies carried out on a sewage treatment plant pay more emphasis on the removal of BOD/COD and SS, not on removal of pathogenic microorganisms. An 18 MLD activated sludge process (ASP), Kankhal and an oxidation pond system, Lakkarghat have been studied for identification of percentage removal of COD, salmonella, TC and FC. The average concentration of COD, salmonella, TC and FC in the nfluent of ASP, Kankhal is found to be 411.26 mg/I, 444, 22.86X106 and 34X105—per100—r—nl:The percentage of removal of COD, salmonella, TC and FC were found to be 36%, 51.35%, 58.88% and 56.05% respectively in PST and overall removals have been found to be 85.42%, 95.81%, 99.95% and 99.48% respectively. At ASP, Kankhal mixing of untreated wastewater (approx. 12MLD) with treated wastewater (approx. 18MLD) results in substantial increase of concentration of COD (=196.84 mg/I), salmonella (=180 No/100 ml), TC (=60.6X105 MPN/ 100 ml) and FC (=26.86X105 MPN/100 ml), which exceeded the limit 1000 FC/100 ml recommended by WHO (1989) for unrestricted irrigation. Also, discharge of mixed wastewater into river Ganga affects its water quality. Therefore, the urgent need to upgrade the capacity of sewage treatment plant (STP), Kankhal, along with provision of disinfection before effluent discharged for irrigation purpose or discharged into river Ganga as river is used for bathing in downstream stretches. iii The average concentration of COD, salmonella, TC and FC in influent of oxidation pond system, Rishikesh has been found to be 466.63 mg/I, 495, 24.82X106 and 108X105 per 100 ml respectively. There are five oxidation ponds in series and overall percentage removals have been found to be 78.25%, 94.39%, 99.45% and 99.49% respectively. The percentage of COD removal is found to be higher in case of ASP system and percentage of bacterial removal was almost same in both ASP and oxidation pond system. The percent bacterial removal per percent of COD removal for oxidation pond system is higher than the ASP system. Since, the oxidation pond system is more economical than ASP system, if there is no constraint on land cost, therefore, the oxidation pond system is found to be more appropriate treatment system for removal of bacterial from wastewater.