When it comes to wastewater and stormwater management, the costs associated with effectively treating it for reuse can be one of the most significant challenges to overcome. In fact, the cost of recycling water – both stormwater and wastewater – may be the #1 problem faced by municipalities interested in reducing their environmental impact.
Every day millions of gallons of potable (drinkable) water are used for flushing toilets. Arguably this drinking water is 100% wasted for this purpose. It is estimated that 25% of our daily household water consumption of between 100-250 gallons of water, goes to toilet flushing.
Meanwhile graywater, which is untreated household waste water that has not come into contact with toilet waste (blackwater) is unused for toilet flushing and other non-potable water purposes.
Graywater examples include water from bathtubs, showers, bathroom wash basins, clothes washers, etc. This water may be cleaner (relative to blackwater) and could be used for the purpose of flushing toilets.
Companies, municipalities and organizations are increasingly asking questions about how our current water conveyance system is designed.
For instance, if the high costs of water treatment could be mitigated by more broadly allocating reused graywater to specific non-potable applications, such as flushing toilets, and incrementally adjusting the level of associated treatment, wouldn’t that be a better solution?
Typically, storm and polluted/waste water treatment can occur in three to five phases in order to meet U.S. Environmental Protection Agency standards, which may include some or all of the following:
- Solids Removal: physical matter, including biowaste, larger than a grain of sand are removed.
- Primary Treatment: water is sent through a settling tank where tiny solid particles can settle to the bottom and any oils can rise to the surface. It then passes through a microfiltration unit.
- Secondary Treatment: microorganisms are introduced to the water to eat any organic matter and the water is heavily aerated, or oxygenated, to support the multiplication of microorganisms.
- Clarification: Either (a) chlorine or another disinfectant are added or (b) reverse osmosis and ultra violet light are utilized to kill off any harmful microorganisms. If a chemical was used, it is then removed.
- Naturalization: the water is then stored in a reservoir for at least six months where it can normalize.
But some are asking, must all recycled water go through equally extensive processes? Since there is considerable demand for even non-potable water, for flushing toilets and municipal irrigation, for instance why not use it for these purposes and save potable water for, well, drinking?
This is a question that private companies such as GE and experts in the public sector (WaterReuse Association) that is garnering increased attention because it makes so much sense. As our world population grows, it is estimated that the demand for drinking water grows twice as fast.