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Background TREATMENT Just as the earth's hydrologic cycle continually recycles water, water is repeatedly cleansed through several natural processes. Solids settle to the botlom of water bodies and impurities are filtered out when water percolates or seeps through rocks, gravel or sand and back into groundwater sources. Organic materials are decomposed by various microorganisms and water-borne patho* genic bacteria, parasites and viruses are destroyed by the sun's ultraviolet rays and other natural mechanisms. Water treatment technology has been developed to mimic nature's cleansing process but at a faster rate. The huge quantities of wastewater produced by urban areas overwhelm the earth's natural recycling process. Consequently, mechanical treatment is necessary to supplement nature's ability. Treatment methods range from basic to advanced and include gravity sedimentation, biological decomposition, filtration, disinfection and membrane technology. Standards for the quality of recycled water and other treated sources in California have increased, giving rise to the development of more sensitive detection and monitoring tests. Likewise, more advanced treatment processes are used to reach the treatment level necessary for the intended usage. Primary, secondary and tertiary treatments are accepted treatments for all uses of recycled water save one: human consumption. To meet the state and federal standards for potable water, advanced treatment using membrane technology is necessary. There are a wide variety of water treatment membranes in which the pore size of the membrane and the amount of pressure needed to filter out targeted contaminants differ. While new membrane technologies are constantly being developed, potential weaknesses with current membrane technology include unidentified tears in the membrane and ruptures in rubber gaskets, a-rings or similar problems according to water quality engineers. This may lead to the risk of pathogens surviving in product water unless they are detected and stopped by downstream barriers. To safeguard against failure, membrane treatment is closely monitored to help ensure membrane integrity. A higher pressure differential of the membrane or the particle count of contaminants in the water may be indicators there is a problem with the membrane. ~ Sewage sludge is a by-product of the primary and secondary sewage treatment stages that must be treated and disposed of. Although typical disposal options include landfill and incineration, biosolids are increasingly being used as soil conditioners to fertilize fiber, animal feed crops on farmland and trees at remote sites, California recycles more than 50 percent of its biosolids, according to the U,S, Environmental Protection Agency (EPA), In 1993, EPA developed minimum standards for site restriction, monitor- ing and reporting requirements to protect human health and the environment. Standards also were developed for heavy metals and pathogens, The land application of biosolids is regulated by the nine California Regional Water Quality Control Boards and in accordance with EPA and state regulations. Despite these regulations, some uneasiness remains over the use of biosolids. The possibility 4 of pathogens and heavy metals, mainly cadmium and lead, have generated concerns. Others are troubled that runoff and deep drainage from fields spread with biosolids could lead to excess nitrogen and groundwater contamination. As a result, Stanislaus, San Joaquin and Sutter counties have banned the use of biosolids on commercial lands. Some farmers welcome the value of biosolids in building soil organics and increasing soil's water holding capacity, but others perceive the use of biosolids on farmland as the dumping of urban waste on rural soils. The city of Los Angeles and Orange County Sanitation District recycle 100 percent of their biosolids, a large portion of which is spread over Kern County farmland, An estimated 1 million tons of biosolids from the Los Angeles area are dispersed (at the request of some farmers) over 40,000 acres of land used for growing non-food crops such as alfalfa and cation.