NITROGEN POLLUTION OF LEACHATE AT A SEA-BASED SOLID-WASTE DISPOSAL SITE AND ITS NITRIFICATION TREATMENT BY IMMOBILIZED ACCLIMATED NITRIFYING SLUDGE

It was found that changes in the nitrogen concentration of leachate fr om the Osaka North Port sea based disposal site were closely related t o the way in which dumping was carried out. The nitrogen concentration of the leachate was low due to the low nitrogen content and slow nitr ogen dissolution rate of materials dumped previously in the landfill. The dumping of incinerator ash, noncombustible garbage, waterworks slu dge and incinerated ash from sewage sludge were followed, and it was f ound that they caused a sharp increase in nitrogen concentration in th e leachate. The main nitrogen form of leachate was NH4-N, and its conc entration reached 50 mg/l after 6 years of landfilling. Successful nit rification treatment of leachate (more than 80% nitrification) was pos sible by using polyvinyl alcohol immobilized acclimated marine nitrify ing sludge with an NH4-N loading rate of 2.9 mg-NH4-N/g-pellets/d. Low NO2-N was detected throughout the continuous nitrification experiment s, so the rate limiting step in the nitrification treatment was reveal ed to be a nitrification step (NH4+-->NO2-). The addition of inorganic carbon to the test leachate enabled us to perform nitrification treat ment even with a high NH4-N loading rate. Dolomite limestone was shown experimentally to be able to replace inorganic chemicals.