The degradation of organic matter by microbial activity under anoxic conditions during transport in tropical sewer systems

摘要

Conventional sewer systems in urban areas are designed and constructed in order to transport wastewater from its sources to treatment plants. The design and characteristics of sewer layout are solely based on hydraulic design, where wastewater quality or biotransformation inside the sewer are not taken into consideration. During the transport of wastewater in sewer systems, many physical, chemical and biological transformations may result in significant changes in the wastewater composition. The microbial transformations can be determined based on three types of conditions: aerobic, anaerobic or anoxic, depending on the type of electron acceptors that present in the wastewater. Each of them produces different processes that will change the quality of the wastewater transported upon its arrival to wastewater treatment plants. Therefore, it is possible to design sewer systems to achieve dual purposes: transport and biotransformation of wastewater. This paper evaluates the performance of laboratory-scale sewer system as a bioreactor under tropical anoxic conditions. Certain parameters were manipulated in order to create and regulate the desired anoxic condition inside the sewer system. Denitrification was enhanced thus removing the easily and slowly biodegradable COD. The overall removal efficiency between 0 km - 3 km samples in the sewer system: suspended solids 58%, turbidity 24%, COD 30% and BOD_5 25%. The results demonstrate that microbial activity or degradation of organic matters are significant inside the sewer system under anoxic conditions. ASM1 was used to analyse the data of this study.