Abstract
This study examined the effects of differences in hydraulic loading and recirculated ratio on the efficiency of removing BOD, T-N and T-P, as well as on sludge produced, in the anaerobic filter bed-biological filtration process combined electrolysis of iron system. The use of an apparatus for removing phosphorus by electrolysis of iron in the anaerobic filter bed-biological filtration process increased its T-P removal efficiency. Stable BOD and T-N removal efficiency was achieved despite different hydraulic loading and recirculated ratio. The optimum recirculated ratio required to remove both nitrogen and phosphorus was 2.8 at a hydraulic loading of 1,000 l·d-1, and 2.8 at a hydraulic loading of 2,000 l·d-1. At the lower hydraulic loading the process had the following domestic wastewater treatment capabilities when the optimum recirculated ratio was set to 2.8: BOD was reduced 10 mg·l-1, T-N 10 mg·l-1, T-P 1 mg·l-1 and SS 10 mg·l-1. The use of electrolysis of iron system in the process resulted in a 25-30% increase in the amount of sludge produced; however, neither its amount nor its properties were affected by differences in hydraulic loading or recirculated ratio, and phosphorus did not dissolve into the surrounding medium again even when the sludge was stored in the anaerobic filter bed tank. In addition, the experiment confirmed that the sludge produced had good sedimentation properties, and so an anaerobic filter bed tank with smaller storage capacity could be used. Thus, this process offers advantages in terms of maintenance and control of the sludge produced.
