Residential grey water recycling system

Abstract

This specification describes systems for the treatment and reuse of greywater and related processes. An exemplary system collects greywater from baths and showers and treats it for use in toilet flushing. Influent bathing water passes through a prefilter to remove larger particles and flows into a greywater collection tank. Collected greywater is filtered through a membrane designed to remove suspended solids. Membrane permeate passes through a sorbent media to remove soluble organics and then flows into a permeate tank. A chemical agent is used to disinfect water in one or more parts of the system and optionally to clean the membranes. A control system manages the operation of system. The system operates in a generally daily cycle with permeation dispersed over a material time, for example 4 or 8 hours or more.

We claim: 
     
         1 . A process for recycling grey water in a residence comprising,
 collecting bathing water in a collection tank;   filtering collected bathing water through a membrane filter to produce permeate;   transferring the permeate to a permeate tank; and,   delivering the permeate from the permeate tank to one or more toilets.   
     
     
         2 . The process of  claim 1  comprising treating the permeate in a sorption unit. 
     
     
         3 . The process of  claim 2  comprising treating the permeate with activated carbon at a surface loading in the sorption unit between 0.4-0.7 m/hr. 
     
     
         4 . The process of  claim 1  wherein the membranes are operated at permeate rate of 10-80 L/hour. 
     
     
         5 . The process of  claim 1  further comprising introducing bubbles below the membranes intermittently. 
     
     
         6 . The process of  claim 5  wherein the bubbles are introduced while backwashing or relaxing the membranes. 
     
     
         7 . The process of  claim 1  further comprising pre-filtering the bathing water upstream of the collection tank. 
     
     
         8 . The process of  claim 7  further comprising backwashing a pre-filter. 
     
     
         9 . The process of  claim 1  comprising a step of adding make up water to the permeate tank. 
     
     
         10 . The process of  claim 1  further comprising a step of transferring water from the permeate tank to the collection tank when required to re-submerge a membrane unit or keep a membrane unit submerged. 
     
     
         11 . The process of  claim 1  further comprising steps of detecting an addition of water to the collection tank or the permeate tank and transferring chlorine to the tank with the added water. 
     
     
         12 . The process of  claim 11  comprising calculating a time that water has stayed stagnant in the tank. 
     
     
         13 . The process of  claim 1  further comprising calculating the water volume in the collection tank and, provided the water level in the tank is within a given range, purging the existing water upon addition of new water. 
     
     
         14 . The process of  claim 1  further comprising hyperchlorinating the membrane filter. 
     
     
         15 . The process of  claim 14  comprising calculating a time from a previous membrane cleaning cycle, stopping permeate flow, adding chlorine to a tank containing the membranes, soaking the membrane, pumping the chlorine solution through the membrane, and purging the tank. 
     
     
         16 . The process of  claim 2  wherein the water is treated to NSF 350 standards. 
     
     
         17 . The process of  claim 1  comprising turning a permeate pump on and off considering sensors in the permeate tank and the collection tank. 
     
     
         18 . A grey water treatment system comprising,
 a collection tank;   a membrane unit in communication with the collection tank;   a permeate tank downstream of the membrane filter; and,   a grey water inlet in communication with the collection tank and adapted to be connected to a grey water drain of a single family residence,   wherein the total volume of the collection tank and the permeate tank is 500 L or less.   
     
     
         19 . The grey water treatment system of  claim 19  comprising a sorption unit between a permeate side of the membrane filter and the permeate tank. 
     
     
         20 . A process for recycling grey water in a residence comprising,
 collecting 150 L or more or bathing water in a day;   filtering 150 L or more of collected bathing water through a membrane filter over a period of between 3 hours and 24 hours to produce permeate; and,   treating the permeate in a sorption unit to create treated water; and,   delivering the treated water to one or more toilets, preferably within about 48 hours of collecting the bathing water.