Water reuse in California
Wastewater can be divided into greywater and blackwater, with the first being defined as water that had been used for laundry, bathing, sink washing, and dishwashers.
[2] The subsequent heterogeneous solution is collected through pipes and the sewer system, and is then treated at a wastewater treatment plant to the standard required according to its intended use.
Historically, this recycled water has been used for agriculture, large-scale landscaping, industrial processes like cooling systems, and groundwater recharge.
[6] Cities in the state began using sewage for irrigation, recognizing it as a source of water and nutrients in an arid California.
Around the same time, the city of San Francisco began using raw sewage for irrigation to create Golden Gate Park, an area which was just sand dunes.
Concerns were raised about public health risks of using sewage for irrigation eventually leading to the first state law regarding the reuse of municipal wastewater in 1918.
[5] After building a treatment plant near Golden Gate Park, artificial lakes and streams were also created with the treated water.
In 1965, San Diego County created man-made lakes using treated sewage for recreational activities, including swimming and fishing.
[citation needed] In 2013, San Diego demonstrated the feasibility of using technology to recycle most of their wastewater for reuse by the year 2035, to decrease costs of importing water.
In the 1930s, San Francisco built McQueen Treatment Plant near Golden Gate Park to treat the wastewater it was using to irrigate the landscape.
This technology included aerating the wastewater to allow bacteria to work on the effluent, as well as adding chlorine to kill off any remaining pathogens.
Currently, reverse osmosis is the technology by which water reuse is made possible, in conjunction with filtering methods for larger solids (e.g., screens and settling tanks), other techniques for removing smaller particulates (e.g., aeration to allow bacteria to metabolize the suspended matter), and chlorination to kill any remaining harmful bacteria.
[9] It also helps to address the unique challenge that California faces in providing water to its densely populated cities and millions of acres of farmland in areas where precipitation scarcely falls.
In cases where the recycled water will not have contact with the edible portion of the plant, like in orchards or vineyards, secondary treatment is deemed sufficient, but in the case of crops with the edible portion of the plant having contact with the recycled water tertiary treatment is regulated.
[4] There are four large-scale groundwater recharge operations in southern California that inject treated wastewater directly into potable water aquifers.
Additionally, water need not be treated to very high standards to be use in industrial applications, and this makes it an even more cost-effective solution.
[3] Although there has been little documentation of adverse effects to humans from water reuse contact or consumption, there remains concern about long-term effects of endocrine disrupters, pharmaceuticals, household chemicals, and personal care products in reused water, including impacts on the natural and beneficial microbiota found on and inside people.
[17] Among many other points, this report clearly states that there is no established and reliable technology to even measure these 'constituents of emerging concern' collectively, as opposed to one by one with expensive techniques, and they cannot be effectively monitored via Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), or Total Organic Carbon (TOC).
The City of San Diego Water Purification Demonstration Project spent nearly half of its budget on public outreach and education in 2005.
