Our Treatment Process
Returning Water to the Environment
The main by-product of ReWa’s water resource recovery facilities (WRRF) is clean, reusable water that is safe to reintroduce back into the environment. ReWa is also responsible for removing contaminants in wastewater that is discharged from houses, industries, and commercial businesses. The treatment process consists of three main steps: primary, secondary, and tertiary treatment.
During the primary treatment process, incoming wastewater flows through mechanical bar screens. These screens remove large material such as rags, plastic bags, diapers, and many other non-flushable items. Once the wastewater is screened, it passes through a grit channel. The grit channel’s design causes a decrease in the water’s velocity. This change in velocity allows heavy inorganic matter, like sand, to settle. The inorganic matter is captured in a hopper and disposed of in a landfill. The final step in the primary treatment process is the sedimentation of suspended organic matter. This process is carried out in primary clarifiers. In the primary clarifiers, the velocity of the wastewater is reduced even more allowing the lighter organic matter to settle leaving a clear layer of wastewater ready for the next treatment process.
Secondary treatment is the next step in the process. In this process, wastewater from the primary clarifier is received in an aeration basin where it is mixed with a mass of beneficial microscopic organisms. Aeration (the addition of dissolved oxygen) is provided, allowing the microorganisms to oxidize the pollutants in the wastewater. Water from the aeration basin is discharged into secondary clarifiers, where the microorganisms are settled leaving clear water ready for final treatment. The settled microorganisms are recycled back to the aeration basin for continuous treatment of the incoming waste stream, or are sent to the digestion process to produce an organic, agricultural-grade fertilizer. Methane gas from the digestion process is recovered and used to generate electricity. Heat from the generators is in turn used to keep the digestion process operating.
In the tertiary process, water from the secondary clarifier travels through deep bed sand filters for the removal of any remaining suspended solids. This is the same technology used for drinking water filtration. Once the filtering process is completed, the water is ready for disinfection. Disinfection kills any pathogens that remain. This is accomplished by sending the water through a series of ultraviolet lights. After disinfection is complete, the treated water is reintroduced back into the river to support aquatic life, recreation, and downstream drinking water supplies.
Since wastewater requires many additional lengthy processes, the cost to purify is high. In contrast to wastewater, drinking water comes from wells or rivers, and is already relatively clean because of the aforementioned process. The extra cost of the processes required to make sure the wastewater is suitable to be placed back into our rivers, streams, lakes, and homes is worth the safety and health of our environment.