Effluent water quality of small-scale On-site treatment facilities for household waste water and nitrogen removal performance with recycle operation

摘要

Practical performance of ten individual type gappei-shori johkasous, on-site treatment facilities for household wastewater, were surveyed during a one year period. Effluent BOD and COD were below 20mg.l~-1 with a cumulative frequency of 70/100 and 80/100, respectively. Mixed liquor in the contact aeration tank was recycled to the first chamber of the anaerobic filter tank in the five facilities of which their airlift type pumps could be used to transfer sloughed biofilm.