Control of production of nitrous oxide from full-scale biological nitrogen removal process in wastewater treatment plant

对污水处理厂进行了实地考察，并进行了实验室试验。Hanaki和Okaniwa调查了一家使用间歇曝气计划的粪便处理厂。考察了不同操作条件下一氧化二氮的生产情况。在反硝化过程中，硝酸盐积累时产生一氧化二氮，在硝化过程中，氨氮积累时产生一氧化二氮。甲醇的加入减少了一氧化二氮的生成。尾气中的一氧化二氮排放量远大于出水中溶解形式的一氧化二氮排放量。排放量随条件变化很大，甚至超过了氮负荷的50%。Hanaki和Matsuo建立了使用氮的稳定同位素作为示踪剂进行实验室规模实验的方法，以确定硝化或反硝化是一氧化二氮产生的主要过程。AOI调查了另一个粪便，以检查一氧化二氮的产生，以及接收生活污水的天然池塘。Tanaka和Sumino考察了使用常规活性污泥和固定化细胞工艺进行硝化的污水处理厂。生活污水中的一氧化二氮小于粪便中的一氧化二氮。固定化工艺比常规工艺产生的一氧化二氮更少。

Surveys of full scale treatment plant as well as laboratory-scale experiments were conducted. Hanaki and Okaniwa surveyed a night soil treatment plant in which intermittent aeration program was used. Nitrous oxide production was surveyed with different operational conditions. Nitrous oxide was produced during denitrification when nitrate was accumulated, and it was produced during nitrification when ammonia was accumulated. Methanol addition reduced production of nitrous oxide. Nitrous oxide emission through off gas was much greater than that contained as dissolved form in the effluent. The emission variates very much depending on conditions and it even exceeded 50% of nitrogen loading.Hanaki and Matsuo established the method of conducting laboratory-scale experiments using stable isotope of nitrogen as tracer to identify whether nitrification or denitrification is major process of nitrous oxide production.Aoi surveyed another night soil to examine the nitrous oxide production as well as a natural pond receiving domestic wastewater. No nitrous oxide was detected in the latter.Tanaka and Sumino surveyed sewage treatment plant using conventional activated sludge and that using immobilized cell process fro nitrification. Nitrous oxide from domestic sewage was smaller than that from night soil. Immobilized process tended to produce less nitrous oxide than the conventional process.