Sustainable Building Technical Manual - Etn-presco.net

methods of dealing with centralized wastewater treatment include land application ofreclaimed wastewater, septage lagoon systems, and composting of sewage sludge foruse as a soil amendment.Diverting or reusing wastewater before it enters the centralized wastewater stream minimizesloading of municipal water treatment plants. As an added benefit, the resultingtreated effluent can be utilized on-site as an irrigation source that contains valuable plantnutrients or as part of a design feature in an attractive landscape.Water diverted from the waste stream is either graywater or blackwater, which requiredifferent on-site handling. Graywater is wastewater generated from indoor uses such aslaundries, showers, and sinks, and can be reused in toilet-flushing or irrigation to helpminimize loading on any type of wastewater treatment system and reduce overall waterconsumption. To utilize graywater, a dual plumbing system must be installed to separateit from blackwater, which is wastewater generated from toilet-flushing. Blackwater can betreated on-site through a variety of conventional or alternative systems.. ☛ SUGGESTED PRACTICES AND CHECKLISTIIndoor Water Conservation❑ Reduce overall water use.Reducing overall water use reduces wastewater. Water-efficient fixtures and appliancesare readily available, including toilets that are virtually waterless. Faucet bubblers, lowflowshowerheads, and flow restrictors further reduce water consumption.❑ Perform a water budget analysis to project the amount and configuration of dailywastewater flows.Estimate water usage and wastewater generation based on standard use patterns andthe number of building occupants, then analyze the figures to determine opportunitiesfor conservation, sources and amounts of graywater available, and other opportunitiesfor efficiency.Graywater Systems❑ Separate and use graywater generated from indoor uses such as laundries, showers,and sinks.Many public and commercial facilities generate relatively small amounts of graywater;other types of commercial and industrial facilities may generate large quantities. Forexample, a vehicle-maintenance facility that uses large quantities of water to washtrucks can realize considerable savings by recycling washwater. Therefore, volumeshould be considered in deciding whether it is cost-effective to treat graywater andblackwater separately.❑ Check with the local health-code department to learn about regulations governingthe use of graywater.Usually, irrigation with graywater is required to be subsurface, although some areaspermit above-ground irrigation. Factors affecting the approval and use of graywaterirrigation systems include soil depth and characteristics as well as drainage and floodingpatterns. Other guidelines include setbacks for graywater irrigation lines fromproperty or potable-water lines. Each state has individualized standards for graywaterirrigation systems. Two states that have standards encouraging graywater use are Texasand California.