Wastewater Treatment and Biogas Production from Air Dried Rubber Sheet Production Wastewater by Anaerobic System

The scopes of this research were to investigate efficiency of anaerobic digestion system to treat wastewater from air dried rubber sheet production process and to produce and use biogas from this system. Wastewater from air dried rubber sheet production process contains high organic substance and pH about 4.6. Therefore, this wastewater must be adjusted pH to be 7 before feeding to system in start-up period. Two tanks system (The system consisted of 2 digestion tanks, each tank was operated at HRT 7.5 days, total HRT was 15 days) provided higher wastewater treatment efficiency than one tank system (The system consisted of 1 digestion tank, it was operated at HRT 15 days). In this research, full-scale reactor (two tank system, total volume was 800 liters) was set up and operated at agriculturist’s home in Nakorn Sri Thamaraj, Thailand. From the first day to the fifteenth day of operating period, wastewater was adjusted pH from 4.6 to be 7.0 before feeding into reactor. After that, reactor was fed with wastewater which was not adjusted pH (pH about 4.6). The results of full-scale shown that this system provided average removal efficiency of COD, BOD, TSS, TKN and TP about 69.23%, 66.86%, 63.16%, 35.81% and 36.74%, respectively. Biogas production rate of full-scale system was 0.45 m3-gas/m3-reactor.day (0.57 m3-gas/kg CODremoved). Total biogas from full-scale reactor (800 liters) was 360 liters per day; it can be used for cooking about 2 hours per day. Compositions of biogas were methane 65%, carbon dioxide 32% and another gas such as nitrogen and hydrogen sulfide 3%.