The Kashima petrochemical complex and the Fukashiba industrial wastewater treatment plant are described. The complex consists of 19 core factories (petroleum, petrochemicals, and thermal power generation) and 39 other factories (including organic chemicals, foods, metals, machinery, etc.). The total amount of industrial wastewater produced is 59,800 m3/day. The treatment plant also accepts municipal wastewater from the surrounding area, totalling 1,100 m3/d. A system for charging for the industrial wastewater has been introduced. The water quality standards for the industrial wastewater discharged to the sewerage system and the effluent of the treatment plant are described. The main treatment process is activated sludge with operational conditions of high dissolved oxygen and long solids retention time (SRT). These operational conditions solved the problems of high ammonia and refractory substances in the influent. Complete nitrification occurred under the low alkalinity conditions and the effluent COD was low due to the long SRT. Successful operation and maintenance were achieved by good co-operation between the factories and the treatment plant.