Water Quality Analyzers for Water and Sewage Treatment

Water is supplied to greater than 95% of Japan, and emphasis is changing to from quantity to quality. As water pollution increases with the advancing industrial age and changes in life-styles, a safer and higher quality supply of city water is desired. In the Special Measures Act and the Work Promotion Act enacted in 1994, the Ministry of Health and Welfare and the Environment Agency stressed the prevention of water source pollution in addition to the previous Water Pollution Control Law and Lakes and Marshes Act. In 1993, the water quality standards for city water were amended. The number of standard items was increased to 46 items. 26 items to be monitored and 13 desirable items were added to supply safer and better tasting water. New treatment systems such as membrane treatment and ozonization have been introduced, and greater importance has been given to water quality control, increasing the demand for new techniques. Only approximately 54% of households in Japan are connected to a sewage system. The promotion of equipment to raise this rate is a major issue. To restore the rapidly deteriorating water environment, improvements in effluent quality related to water pollution control in public water areas is also an important theme. The effluent quality has been strictly controlled by strengthening effluent standards, total emission controls, and enactment of more stringent prefectural effluent standards. Advanced treatment systems for denitrification and phosphorus removal have had positive results when used in sewage disposal plants, and it has become more important to reliably demonstrate the performance of water quality control treatments. Because of the increasing expectation of users regarding water and sewage treatment of the changing environment and the advance of water quality measuring technologies, new on-line water quality sensors, in addition to conventional sensors, have been developed and introduced with positive results. This paper describes the process flows of water and sewage treatments, all types of water quality sensors (from basic models to those based on new principles), and water quality control in water and sewage treatment processes.