Waste from baths, showers and washing machines is grey water, it looks cloudy in appearance and can be filtered for reuse. Water from the kitchen sink, dishwasher and toilet cannot be used because it has far too many contaminants such as bacteria, greases and chemicals. Black water is extremely toxic and should be sent down into the sewerage system where right treatment is possible. Whilst grey water contains soap, detergents, hair and bacteria; it still can be recycled through water system that consists of filters and purifiers. Once this process is complete the water is clean enough to be used for watering gardens including vegetable patches.
Grey Water Management
Drain pipes from bathrooms and kitchen are extended to an underground collection tank via a strainer. The strainer traps particulate matter, hair and other contaminants lager than 0.3 mm. The tank is sized as per water required per day (excess water if collected is drained). The collected water is passed through fine sand filter to remove dust, sand, dirt and other solid particulate matter up to 50 micron size. Then water is ozonated to destroy organic matter, oils, soaps, color, odor and bacteria using a process known as advanced oxidation. Finally the water is filtered using a 10 micron bag filter. The ozone system (heart of equipment) is selected on quantity of water treated per hour and level of oxidation required (COD). Generally for domestic gray water a level of 50 grams of ozone for 1000 liters of water (50 ppm) is considered sufficient.
Using ozone for grey water recycling it has many benefits. Ozone is a very reactive gas that can oxidize bacteria, moulds, organic material and other pollutants found in water. Ozone kills micro organisms effectively and achieves effective disinfection. It reduces COD and BOD levels. No nasty odors or residue/sludge produced from the treatment. Ozone converts back into oxygen quickly, and does not leave harmful by- products.
Recycling of grey water offers many benefits like reduction in use of fresh water sometimes by half! Grey water makes up the majority of the household wastewater stream, so diverting it from the septic system extends the life and capacity of the system. For municipal systems, decreased input means more effective treatment coupled with cost savings. Grey water recycling for irrigation replenishes groundwater, helping the natural hydrologic cycle to keep functioning. Grey water can support plant growth in areas that might otherwise not have enough water. The nutrients in the grey water are broken down by bacteria in the soil and made available to plants. This helps to maintain soil fertility. The quality of groundwater and surface waters are much better preserved by the natural purification processes the grey water undergoes in the top layers of the soil than by any engineered water treatment. The grey water user gets the satisfaction of direct participation in the responsible management of global nutrient and water cycles.