I Page 6 RAIN December 1977 Low-Flow Wastewater No meaningful standards have been developed yet for the quality of water released from greywater treatment. The following elements have been designed for or used in lowdischarge households, and can m·ostly be duplicated or used in sequence for more complete treatment or to handle larger volumes. Use the common-sense approaeh- start with nothing and add piece by piece until you get the water quality you need. Suburban America generates 25 to 60 gallons ofgreywater per person per day- an average of 30 gallons. That can be much less. Ten gallons per person per day is a reasonable estimate where water conservation practices are followed. Use the Rules of Thumb and Nose to figure what you need. Let us know of other better designs, or bow these work/don't work for you. -TB - A simple system has been proposed by septic tank consultant Tim Winneberger for treating small volum~s of wastewater that has few suspended solids. The settling tank is a 30-gallon plastic garbage can with lid, used to trap grease or other float~ ables that would clog seepage pit. The check tank is a fivegallon plastic bucket with lid. The pipes are one-inch plastic. Where high ground water isn't a problem, the settling tank can be surrounded by rocks which allow water to seep into the ground as illustrated. With high groundwater, the effluent pipe and rock fill are omitted and wastewater piped to a regular leaching line near the ground surface. When you check the check tank and find grease or other floatables, it's time to empty the settling tank and bury the contents. The three- or four-inch observation pipe is notched or has holes in the side so the water level in the seepage pit can be checked and seen if it is overloaded. If so, a leach line can be added where 'arrow says "to field." See ?AT Report for more details. Sand filters give excellent BOD removal (removing the Biological Demand for Oxygen by bacteria that break organic matter down into simpler compounds), and also pathogen control. Allow one square foot of surface for every six to ~ight gallons of ,water flow per day-a 55-gallon drum will treat 25-5 0 gallon·s per day. A 3o~inch depth of sand is adequate. Sand filters fail if continually saturated, so need cover in rainy weather and perform better if alternated filters are used.' Occasional backwashing with clear water and removal of top inch or two of s.and is needed. See VITA Village Technology Handbook for more details. Most·health officials still see red at the mention of direct. surface application of greywater, though in drought areas they have conveniently looked the other way. No modern testing , seems to have been done to determine what, if any, real health hazards exist when soil is used as the simplest natural veatment for nutrient removal and pathogen destruction. Farallones Urban House has been using an elegantly simple method for some time now. Both urine and greywater are drained to a 55gallon drum, where the urine.is diluted by the greywater and its nitrogen content used to balance the fertilizer value of the.· phosphorous in the greywater from soaps. A garden hose distributes the water to desired areas of the garden, where a cloth bag tied to the end of the hose retains large pa,rticles and prevents soil erosion. The bag should be washed or changed weekly. See the Farallones Greywater Reports for more details. -
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