Waste Water Treatment Process
All influent flow into the treatment plants comes through the main lift building. This building houses equipment for preliminary treatment and pumps for transferring the wastewater for further treatment.
Evenly spaced bars in the channel remove large solids and trash such as rags, wood, and rocks. This material is cleaned from the barscreens with a mechanical rake and disposed of in a landfill. Removal of these materials helps prevent clogging of pipes and protects mechanical equipment from excessive wear.
The baffles slow the wastewater down so that the grit collector removes materials such as rocks, sand, cinders, and other large heavy materials. This process removes materials from the wastewater that would otherwise settle in tanks and digesters or clog pipes and cause wear on machinery.
The wastewater treatment plant utilizes pumps of various sizes to lift water to the top of a hill to begin treatment. Since this is the highest point the wastewater will reach in the treatment process, gravity will move it down through the rest of the plant.
Next, wastewater reaches a pair of primary clarifiers where it will rest for two to three hours, allowing solids to settle or float so that the mechanical rakes can remove it. These collected materials are sent to digesters for treatment.
The Aeration Basins are the major component of wastewater treatment process, where we rely on microorganisms to consume, convert, and/or breakdown pollutants. Operations staff keeps the preferred organisms alive to achieve the necessary treatment use air supplied by blowers.
The Secondary Clarifiers remove the solids just like the primary clarifiers. Once collected by the mechanical rakes, the sludge moves to the digesters for treatment or returned to the aeration basins to maintain microorganism populations.
These large holding ponds helps reduce more suspended solids and BOD concentrations in wastewater treated through the plant. These ponds hold a capacity of 6 million gallons and provide a detention time of 24 hours.
Dissolved Air Floatation
Solids removed in Secondary Clarifiers are pumped to a Dissolved Air Floatation Tank for thickening. Fine particles of air force the sludge to float to the top, where the thickened sludge is removed using the mechanical rakes. The thickened sludge pumped to digesters for treatment, while the water that goes back to the head of the plant for treatment.
The digester building consists of four large tanks designed to treat the solids through the wastewater treatment processes. In the digesters, the solids cook for minimum of 15 days at a temperature greater than 95° F by pumping sludge through tubes with hot water (a heat exchanger). We then again rely on microorganisms to break down organic matter, providing solids reduction and killing pathogens. The biosolids are then handled as a liquid at a range of 2-4% solids. An average of 30,000,000 gallons of biosolids get treated each year and used as fertilizer through our land application program.
Prior to the land application, the biosolids receive an analysis to determine nutrient and metals content. Tanker trucks transport liquid sludge to permitted sites for land application to crop and pasture land. TRU maintains around 2,000 acres of private farmland and TRU’s 600+-acre Resource Recovery Farm for land application.
Resource Recovery Farm
TRU’s Resource Recovery Farm (RRF) was established in 1994 on 600+ Acres of Gastonia owned land located between Dallas and Cherryville. The Farm provides a place where a biosolids storage facility was constructed and where land is utilized for the land application of Biosolids from TRU’s treatment facilities. The RRF is a public-private partnership between TRU and EMA Resources, Inc., a biosolids management company. TRU is responsible for the infrastructure and maintenance improvements to the RRF and Otter Creek is responsible for the day-to-day operation and management of the RRF. Otter Creek subcontracts the actual farming on the RRF to a local Gaston County Farmer.
In 1997, TRU received the United States Environmental Protection Agency (“USEPA”) Region IV First Place Award for Beneficial Use of Biosolids for its Biosolids Program, which included the Resource Recovery Farm. In addition, TRU received an Honorable Mention at the National level. These awards recognized TRU’s activities for demonstrating biosolids management practices, which are environmentally safe, economically attractive and acceptable to the public.
The Resource Recovery Farm is equipped with two lined biosolids storage basins with a combined capacity of 8 million gallons and the equipment to mix and load the solids onto application vehicles for land application on the 200 acres of permitted crop and pastureland located on site or the other 1800+ acres located throughout Gaston County. These basins for biosolids storage when weather restricts land application.