Performance of the three-stages anaerobic tofu wastewater treatment during the second start-up process

Abstract

Tofu industry in Indonesia develops rapidly with the demand of the community. Therefore it is necessary to pay attention to the condition of liquid waste as the by-product of the industry. Traditionally, small- to medium-scale tofu industries produce highly polluted wastewater in compare with the big industries. For this reason, research on the tofu wastewater treatment was carried out to study the stability of anaerobic process in a three-stages packed-bed system after two months of pause or no-feeding process. The experiment used tofu wastewater from one of the factories in Bandung; the untreated wastewater had 15.9 g/L of COD at pH 3.5. Observations were carried out for 26 days. The system consisted of three similar reactors that worked in serial; each has the capacity of 10 litres. Tofu wastewater was introduced from the bottom of the reactor flowing vertically upward to the outlet. The outlet of the first reactor flow to the bottom inlet of the second reactor, and subsequently the outlet of the second reactor fed the third reactor. Each reactor was placed at different altitudes to facilitate gravity flow from one reactor to the next at the same rate. The results of the experiment show that the system overall worked well in a continuous flow rate. The COD value could decrease from 15.9 g/L to 7.4 g/L on average at the third reactor, as well as the pH changed from pH 3.5 to 7.