Abstract:
tanks are widely used in rural and urban areas treating domestic wastewater from individual and cluster of houses, however, due to their low treatment and biodegradation capacity, they are still considered as intermediate (primary) treatment option leading to several basic health and environmental risks. In this regard, a study has been made on a modified septic tank by submerging a membrane module having pore size 1-3 μm inside the wastewater between the settled sludge and floating scum termed as Membrane Based Septic Tank (MBST). Introduction of membrane filtration further enhanced the treating capacity with safe effluent disposal or reuse in agriculture and horticulture. During 100 days of continues operation and monitoring, spiral design membrane module with 1 m2 effective area was used. This system was found to produce satisfactory results, where the average removal efficiencies of COD, BOD5, TSS, phosphate, nitrate, nitrite, ammonium and total-coliform were 71, 76, 82, 47, 48, 40, 27 and 88%, respectively. However, during the filtration process, membrane fouling was found to be the major limitation for MBST system. Membrane fouling characterization was performed by developing trans-membrane pressure (TMP) profiles. The system was operated at flux rates of 6, 8 and 10 L/m2-h (LMH) and fouling frequencies were found to be at 15, 8 and 5 days, respectively at terminal TMP of 60 KPa. Membrane was physically cleaned and examined for membrane resistance analysis after each operating cycle. Physical cleaning was found to be effective in removing cake layer resistance while pore blocking resistance progressively increased after each filtration cycle. The system has shown effective treatment efficiencies on a much lower capital and simple design compared to high cost membrane systems.
