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Recent improvements at the Triangle Wastewater Treatment Plant include:

- A Recycled Water Facility, completed in February 2012, consists of four turbine pumps, a hydropneumatic tank, a 500,000 gallon storage tank, instrumentation and metering, a dual disinfection system and a distribution system.

The facility’s effluent receives secondary disinfection with sodium hypochlorite to become recycled water and to provide disinfection in the distribution system. The recycled water system is designed to pump as much as 5.2 million gallons per day. The water is continuously monitored for turbidity and total residual chlorine.

Recycled water is a valuable community asset for: landscape irrigation, cooling towers, and construction activities. In addition, at the Triangle Wastewater Treatment Plant, it is used in the administration building for cooling systems and water closets.

In the Research Triangle Park, having a redundant water supply is important for water critical facilities, such as: computer database facilities, pharmaceutical plants, LED manufacturing plants and agricultural greenhouse research and development facilities.

R.W. Pump Station  R.W. Tank

   Recycled Water Pump Station               Recycled Water Holding Tank


- A new Sludge Handling (Biosolids) Facility, completed in February 2013, consists of two aerated sludge holding tanks with the capacity to hold 1,000,000 gallons, three Alfa Laval G2 centrifuges, and an automated truck loading station.

Excess biomass flows to sludge holding tanks. The waste sludge thickens by gravity and the supernate is decanted into a side stream equalization tank. The thickened sludge (1% dry solids) is aerated and mixed to ensure a uniform sludge solids concentration and to minimize anaerobic conditions.

Polymer is added to the thickened sludge before it moved to the centrifuge where a cake sludge (20% dry solids) is produced. The cake sludge is pumped to trailers before transport to facilities for stabilization and distribution.

In 2013, the sludge cake was processed to produce a Class A compost primarily used for the commercial landscape market. Future improvements for biosolids processing may include a Class A stabilization through energy efficient processes such as active solar drying.


Sludge Handling Facility Centrifuges


Future Projects in Planning Stage

Extension of Recycled Water System: The first phase of the recycled water system has been installed. The next phase will extend the distribution system further north to BASF and terminating at the Research Triangle Park Phase One Redevelopment site. Future phases will extend the distribution system under Interstate 40 to RTI, IBM and the Research Triangle Park Phase Two Redevelopment site.

Waste to Energy: Wastewater treatment residual biomass is currently being dewatered for off-site composting into a Class A biosolid. Alternatives to use this biomass in a more sustainable manner will be considered. Alternatives which may be considered include: thermophilic anaerobic digestion, hydrolysis, active solar drying, waste to energy conversion, or a combination of these alternatives.