Bio-treatment of saline wastewater generated by using seawater flushing toilets

There is very little known about the feasibility and effectiveness of biological treatment for saline wastewater generated by using seawater for flushing toilets. Therefore we devised experiments to examine the treatment of highly saline wastewater resulting from using seawater for flushing toilets to explore the feasibility of treating saline sewage by biological processes, effects of salinity on bio-treatment system and the behavior of activated sludge system during salinity shock. Lab scale sequencing batch reactors (SBR) were initially operated at low, and then at increasing salt levels. The microbial populations during these experiments were monitored to determine the specific effect of salinity on the various bacterial groups responsible for pollutants removal. The performance of system was evaluated under different operating conditions such as salt concentration. The results indicated that although high salinity inhibited the microbial growth and decrease organic matter degrading velocity and removal efficiency, the saline sewage with blew 20g/L salinity can be treated by biological process. The increasing salt concentration decreased the yield of biological solids and changed the structure of microorganism ecology. High salinity bettered settleability of activated sludge and changed the structure of activated sludge floes. Shock of salinity can cause upset of disposal system not only when increasing influent salinity but when decreasing influent salinity. However, when increasing salinity the elapsed time needed restoring was longer than when decreasing salinity. These research results are attributable to flexibilities of operation in a full-scale treatment plant processing saline sewage.