Enhanced Primary Treatment of Black Water Using Two-Stage Onsite Sanitation System

Abstract

A study was conducted to evaluate the treatment efficiency and applicability of a novel two-stage anaerobic onsite sanitation system to improve primary treatment of black water generated at a residential school. The system was designed to accommodate two bioreactors. The first reactor was a modified septic reactor and the second one was an upflow anaerobic reactor. Both reactors were contained in a compact single unit. The system began functioning with no inoculum. It was able to deliver considerably high removal efficiency of 72.6%, 81.4%, and 83.2% for chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS), respectively. The fecal coliform removal in the system was observed to be 2.84 log. The analysis of accumulated sludge within the system was categorized as high-strength fecal sludge. This system has a simple design and requires less maintenance. Moreover, it involves low cost and requires no electricity. Thus, the system promises to be a better replacement for the conventional septic tank for a better primary treatment of black water in unsewered areas of developing countries such as India.