Abstract:
The objective of this research is to study the improvement of an Auto Part factorys wastewater treatment plant by using a Semi-Continuous Activated Sludge system and chemical coagulation.The results obtained show that, at the flow rate of 120 m3/d of the wastewater from the manufacturing process, SS, BOD5 and COD could be removed by coagulation using aluminum sulfate with efficiencies of 97.20, 97.10 and 91.80 %, respectively. The treated wastewater was then mixed with the wastewater from the office which had a flow rate of 210 m3/d. Then, the optimum condition for treating this wastewater by using Semi-Continuous Activated Sludge was studied in a 150-liter reactor. A 3-hour treatment cycle was found to be suitable, which included 1 hour for fillaerating,
1 hour for fill-settling and 1 hour for decanting. By varying the F/M ratio from 0.07 to 0.10, the removal efficiencies of BOD, COD, TKN, PO43- and Fe were 9.06 -5.42, 79.2 - 61.6, 29.24- 26.43, 2 - 1.65 and 0.185 - 0.15 mg/l, respectively. All values were complied with the Ministry of Industry (MOI) standard of Thailand. The results from this study were applied for a design of a Semi-Continuous Activated Sludge system. By using the reaction rate constant of 0.0759, the
wastewater flow rate of 330 m3/day and the F/M ratio of 0.07, the volume of the Semi-Continuous Activated Sludge system was found to be 300 m3. The system would be operated at 8 cycles/day, which could treat 41.25 m3 of wastewater per cycle.