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Ridgemark Wastewater Treatment Plant


The Ridgemark Wastewater Treatment Plant was completed in 2013 and treats sewage from Ridgemark, Quail Hollow, and Oak Creek. In order to meet the more stringent regulations on treated wastewater quality, Sunnyslope replaced it previous aerated pond wastewater treatment with a new sequential batch reactor treatment plant. Through this Sunnyslope is meeting all the treated wastewater quality regulations that the plant was built to address.

Treatment Process

Solids Removal

When wastewater first enters the treatment plant from Sunnyslope's wastewater collections system, it passes through a screen to remove any large solid material. This can include "flushable" wipes, hygiene products, plastic, trash, and other solid waste that people send down the drain. (Please be good sewer customers and ONLY flush toilet paper down the toilet. "Flushable" wipes do not break down in the sewer system and can cause blockages.) Wastewater then passes through a grit conveyor to remove sand, gravel, and other fast-settling materials.

Sequential Batch Reactor

Wastewater then flows through meters and into the one of the sequential batch reactor basins. All the biological wastewater treatment processes happen within each basin. Basins progress through the full biological treatment process as the wastewater remains in the basin. This allows for a much smaller footprint, especially for a small plant like this one. 

Anaerobic mixing

The first stage in the process is anaerobic (without oxygen) mixing. During this stage, the incoming wastewater is thoroughly mixed with the wastewater already in the basin. This creates a fairly even distribution of the organic material and microorganisms in the wastewater (also called mixed liquor). 

Aerobic Treatment

After the mixing stage, large volumes of air are pumped through bubble diffusers in the basin to quickly add lots of oxygen to the mixed liquor. This oxygen rich environment encourages the mass growth and reproduction of bacteria that convert organic molecules and ammonia to nitrite and then nitrate through a process called nitrification.  

anaerobic settling

Once bacteria have converted most of the ammonia to nitrate, air stops being added to the mix liquor. The bacteria continue to consume the oxygen until there is almost none left. The sludge begins to settle toward the bottom of the basin. Without oxygen, other bacteria begin to grow and reproduce. These microorganisms convert nitrate into inert nitrogen gas (which makes up about 78% of the atmosphere). As the sludge continues to settle, the water at the surface starts to become clear.


After the now treated wastewater has sufficiently settled, a decant trough is lowered which skims the treated wastewater from the top. That water is now fully biologically treated and environmentally safe for disposal.


Treated wastewater that has passed through the full sequential batch reactor process is piped to one of Sunnyslope Water's four percolation disposal ponds. These ponds primarily percolate the water into the ground although some water will evaporate into the atmosphere. As the water slowly moves down into the ground, the soil particles further filter it and remove any other organic substances. Additionally, bacteria and microorganisms in the soil also provide additional treatment. By the time the water reaches the groundwater table, it has been cleaned of its organic contaminants and is safe.

Sludge Treatment

Throughout the sequential batch reactor process, the bacteria that treat the mixed liquor produce a concentrated sludge which accumulates at the bottom of the basins. Sludge removal pumps transfer the sludge water to a large sludge treatment tank. In this tank, anaerobic bacteria continue to break down the organic material in the sludge. The treated sludge settles to the bottom of the tank where the weight of the water above it causes it to thicken. The clearer water near the top of the tank is decanted and sent back through the sequential batch reactor. Once the sludge has matured, it is pumped from the bottom of the tank into the drying beds. Here the last of the water dries out of the sludge. Once dry the sludge can be removed and taken to the landfill for disposal.

Operation and Control

Sunnyslope staff operate and maintain the Ridgemark Wastewater Treatment Plant. An army of sensors and instruments constantly feed information to the operators concerning every stage of the treatment process. Regular laboratory testing is done to ensure that each process is effective and that the treated water is environmentally safe for disposal. Emergency power generation is onsite and routinely tested so that the plant can remain operational even during a power outage. The SCADA electronic control system allows operators to monitor and control the plant operations remotely at any time.