WATER-QUALITY STUDY OF GRAYWATER TREATMENT SYSTEMS

A residential single family dwelling was retrofitted to recycle graywa ter for landscape irrigation and toilet flushing. The objective of thi s study was to determine improvements in graywater quality by evaluati ng five simple graywater treatment systems that were easily adapted to the household plumbing. The treatment systems consisted of (1) water hyacinths and sand filtration, (2) water hyacinths, copper ion disinfe ction, and sand filtration, (3) copper ion disinfection and sand filtr ation, (4) copper/silver ion disinfection and sand filtration, and (5) 20-mu m cartridge filtration. Water quality parameters measured were fecal and total coliform indicator bacteria, nitrates, suspended solid s, and turbidity. Reductions in bacterial concentration, suspended sol ids and turbidity were achieved by all systems tested. Treatment reduc ed nitrate concentrations to an average of 2.6 mg/liter. Reductions in suspended solids, and turbidity were influenced more by the quality o f the graywater entering the treatment system than the efficiency of t he systems themselves. The water hyacinths and sand filtration system provided the best graywater quality in terms of the concentrations of fecal indicator bacteria. The system providing the best water quality in regard to average suspended solids after treatment was the water hy acinths, copper ion, and sand filtration system, and the best average turbidity was achieved by the copper/silver ion generating unit with s and filtration. All systems were capable of significant reductions in fecal indicator bacteria, suspended solids, and turbidity; however, ad ditional treatment or disinfection would be necessary to further reduc e the level of coliform and fecal coliform bacteria to achieve regulat ory standards in the State of Arizona