Graywater is a potential water source for reducing water demand. Accordingly, a review was undertaken of graywater reuse regulations and guidelines within the 50 United States. Major issues considered included acceptability for graywater segregation as a separate wastewater stream, allowable graywater storage, onsite treatment requirements, and permitted graywater use applications. Existing regulations and plumbing codes in the different states suggest that there are impediments to overcome but also potential incentives for graywater reuse. It is encouraging that regulations in 29 states promote safe graywater reuse, but there are also inconsistencies between plumbing codes and other regulations within and among the 50 states. Impediments to graywater reuse include disallowances of graywater segregation or collection, and restriction of graywater reuse to mostly subsurface irrigation with limited indoor use permission. Ease on restrictions and guidelines to promote development of low-cost and proven treatment technologies are needed to promote graywater reuse.
A cost–benefit analysis of onsite graywater recycling in single‐family and multifamily homes was conducted to evaluate the merits of graywater recycling in the Los Angeles, Calif., area. Graywater recycling reduces potable water demand by 27 and 38% in single‐family and multifamily homes, respectively. The estimated available graywater is equivalent to 25% of the city's water demand. At a participation level of 10%, Los Angeles will be able to reduce water supply and treatment‐related energy by 43,000 MWh/y, potable water demand by 2%, and wastewater treatment load by 3%. Amending local building codes to require new construction to include plumbing to divert graywater for reuse can lower retrofit costs. Financial tools (e.g., a rebate program, a third‐party ownership model) could lower cost hurdles for graywater recycling. A city‐wide graywater reuse program could be developed to satisfy regulatory requirements by monitoring system operations and maintenance by certified contractors.
Available online xxx Keywords: Graywater treatment Vertical flow wetland Nonpotable water reuse Biofilm Semi-batch A B S T R A C TThe technical feasibility of graywater treatment, via a semi-batch vertical flow wetland (SB-VFW), was evaluated at a single family home for aboveground water reuse. Graywater treatment was achieved to a quality level that was well within the regulatory compliance limits (e.g., with respect to biochemical oxygen demand (BOD), total suspended solids (TSS) and turbidity) for above ground reuse. System performance over the course of a five-month field study demonstrated that the necessary treatment time was typically $3 h for a 300 L batch. The SB-VFW operated in a stable manner owing to the use of a coconut soil substitute that has high hydraulic conductivity and also enabled avoidance of clogging due to excess biofilm growth. The latter was made possible through the use of a bio-based laundry (BBL) detergent which had a lower organic content relative to conventional laundry detergents. The system was able to return to normal operation even after detergent shock loads. Results of the present study are encouraging and suggest that residential level graywater treatment is technically feasible and can thus potentially expand the range of possible water reuse applications.
Climate change and urbanization pressures in parts of the world characterized by water scarcity have strained resources to the point that many water purveyors must operate within more of a closed urban water cycle by using alternative sources while continuing to protect public health.
She specializes in water resource management, including onsite nonpotable water treatment and reuse, and water sustainability and risk assessments. She also has other environmental consulting experience, including environmental impact assessment studies, stormwater fee analysis, and environmental due-diligence auditing. Yu received her master's degree in environmental engineering from Hong Kong University of Science and Technology and her doctorate in Yu et al. | http://dx.
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