ผลของการเติมเชื้อทางการค้าในถังเติมอากาศต่อประสิทธิภาพการบำบัดน้ำเสียจากโรงอาหาร

Abstract

Electrical and electronic industries are Thailand's important sectors with continuous growing. This growth, however, leads to several environmental problems. Hana Microelectronics Public Co., Ltd. is one of electronic assembly factories having more than 3,700 staff. One of factory's environmental problems is increase of wastewater generated from the canteen. As numbers of staff have been increased every year, the factory has to monthly pay the high amount of money to the Northern Region Industrial Estate. The current wastewater treatment process is the biological activated sludge with plastic media addition (known as the Integrated Fixed-film Activated Sludge: IFAS). This process has occasionally not performed at the level set by the factory. To solve the problem, addition of commercial inoculum has been implemented when sludge concentration (SV30) is lower than 300 mg/l and this practice has increased the factory expense. This independent study aimed to investigate effects of commercial inoculum addition in aeration tanks on canteen wastewater treatment efficiency. Four 20 1 lab-scale reactors (R1, R2, R3 and R4) with plastic media addition at 20% of effective volume, the same as the full-scale system used in the factory, were used in the experiments. Wastewater from the factory canteen was fed to each reactor at the HRT of 8.8 d. All reactors were started-up with inoculum from the full-scale sedimentation tank at the volume of 80 1. RI was used as the control reactor without any commercial inoculum addition, while R2, R3 and R4 were added with the commercial inoculum at the volume of 12.5, 25 and 50 ml, respectively, every 14 d. Results showed that the raw wastewater contained high concentrations of organic substances both in forms of BOD and COD. These concentrations were in the high concentration range for domestic wastewater. However, majority of organic substances were found to be easily biodegradable. Total BOD of raw wastewater was quite fluctuated owing to changes of raw materials and types of food. Filtered BOD concentrations of treated wastewater from R1-R4 were not significantly different, which was equivalent to BOD removal efficiencies in the range of 99.1-99.3% regardless of the addition of commercial inoculum. Higher suspended solid concentrations were detected in reactors with commercial inoculum additions. It was found that sludge concentration measurement using SV30 did not represent all amounts of microorganisms in the reactors as both suspended and fixed-film microorganisms existed in the IFAS. At steady-state conditions, microorganisms could provide adequate efficiency in treating wastewater to meet the effluent standards set by both the Ministry of Industry and the factory without any addition of commercial inoculum.