Sustainable Building Technical Manual - Etn-presco.net

❑ Install dual plumbing lines in building interiors.Dual plumbing separates graywater from blackwater. Dual plumbing is not difficult toinstall, but is most-cost effective if done during initial construction. If dual plumbinglines are not installed initially, adding a graywater treatment system later can be quiteexpensive. For this reason, install dual distribution lines in new facilities if a graywatersystem may be incorporated in the future.❑ Utilize graywater for nonpotable purposes.Recycle graywater via a dual distribution system, for such nonpotable water uses as toilet-flushing,thereby avoiding unnecessary use of high-quality potable water. Anothermajor use of graywater is for irrigation of areas such as golf courses, ornamental landscapes,and turf areas. A separate tank, filter, and special emitters are necessary in graywaterirrigation systems. Types of irrigation systems that can utilize graywater include:(1) drip irrigation with pressure dosing, which uses a pump system to “dose” the irrigationwater at regulated intervals; (2) more traditional evapotranspiration systems; and(3) shallow trench systems, which utilize distribution pipes placed close enough to thesurface to allow for irrigation of plant roots (Figure 6). In some areas, above-ground orspray irrigation is possible.Blackwater Systems❑ When possible, treat blackwater from toilet-flushing with on-site systems.– Utilize innovations such as low-pressure dosing systems in conjunction with septictanks to overcome limitations of soil, geology, or topography.– Consider biological systems such as constructed wetlands. Constructed wetlands areartificial wetlands used for waste treatment. As wastewater flows through the wetland,plants and naturally occurring microbes remove waste. This technology can beused at a variety of scales, from wastewater treatment for an individual building totreatment for entire communities. Two types of systems, the surface-flow wetland,and the subsurface-flow wetland, can be utilized. Surface flow wetlands, also calledwastewater lagoons, usually use a tiered system of ponds with wetland plants totreat wastewater. Subsurface-flow wetlands, also called microbial rock plant filters,are soil-less, and utilize a gravel medium to anchor plants. Wastewater flowsthrough the gravel and is not visible at the surface. Effluent from both types of systemsmust be handled through irrigation or other methods.– Consider sand filters and aerobic tank treatment. Sand filters, a low-cost wastewatertreatment technology, have been in use for many years. Aerobic tank systems offeradvantages over traditional septic tanks, which do not use oxygen to treat waste.– Consider composting toilets. Composting toilets are a nearly waterless technologyfor dealing with human waste, combining the waste with organic material, such aslawn clippings, to produce a nearly odorless product that can be used as a soilamendment. Large-scale composting toilets capable of handling large numbers ofusers are available commercially. This type of technology is being applied at themunicipal scale through a practice known as “sludge composting.”– Consider aquaculture systems. In aquaculture systems, wastewater becomes a sourceof food for plants and fish. In the process, water is purified, as plants and fish ingestpollutants. This type of system requires high management, but produces food andfertilizer in return.❑ Check with the local health-code department to learn about regulations governingblackwater systems.Treatment and definitions of blackwater vary—in some jurisdictions, blackwater iswastewater generated from toilet flushing; in others, it includes water from kitchensinks or laundry facilities.