Operations
Water Reclamation Facilities
The Lower Poplar Street Water Reclamation Facility
The Lower Poplar Street Water Reclamation Facility (WRF) opened in 1959 to provide treatment for municipal and industrial waste within the service area that extends north of Macon along the Ocmulgee River, within Bibb County.
With an original wastewater treatment capacity of 12 million gallons of wastewater per day (MGD), the Authority has upgraded the Lower Poplar Street Plant with highly sophisticated processes that expanded its capacity to 20 MGD. Thus, the plant now features the most recent advances and innovations in wastewater treatment. A vehicle maintenance shop has been added to the Lower Poplar Street Facility to allow MWA personnel the capabilities to perform necessary maintenance for fleet vehicles and plant equipment.
The wastewater treatment process
The Lower Poplar Street WRF is an advanced secondary wastewater treatment facility utilizing a coupled filter tower/activated sludge process. The major treatment stages at the facility involve preliminary, primary, and secondary wastewater treatment, as well as sludge handling.
Preliminary treatment at Lower Poplar entails the removal of larger solids and grit out of the wastewater through a process involving four barscreens and two grit chambers. The barscreens remove solids from three-eighths of an inch and above. The grit chambers remove detritus material from the wastewater, such as sand, coffee grounds, etc. This material is abrasive to the equipment and will take up unnecessary room in the digestors if not removed at this stage. Material removed from the barscreens and grit chambers is disposed in a landfill.
During the primary treatment of wastewater, the flow is slowed down to allow solids to settle and be removed from the water and pumped as sludge to the digesters for further treatment through the use of two circular primary clarifiers, as well as additional, rectangular primary clarifiers.
After the wastewater leaves the primary clarifiers, it enters the secondary treatment stage. The MWA's advanced secondary treatment of wastewater utilizes two filter towers and four activated sludge aeration basins.
The filter tower/activated sludge process is an advanced biological secondary treatment system. This system utilizes microorganisms such as bacteria and protozoa, fungi and invertebrates, to produce an acceptable effluent quality by removing substances that have an oxygen demand. In doing so, the treated wastewater is safe and approved for disposal into the receiving stream, according to the provisions of the Authority's regulated permits for this form of direct discharge into a water body.
As for the sludge exiting the aeration basins, it is sent to three final clarifiers. In the final clarifiers, the sludge settles to the bottom and is collected and sent back to the head of the aeration basins to mix with the incoming wastewater. In order to keep the sludge fresh and the micro-organisms active, a portion of the sludge must be disposed on a regular basis.
The clean water from the final clarifiers flows over weirs and by gravity through the effluent flume to the chlorine contact chamber. At this stage, chlorine is added to kill any pathogenic organisms in the water. After enough contact time is given for sufficient kill in the chlorine contact chambers, the water is de-chlorinated by sodium bisulfate. The final treated water is then discharged to the river by the effluent pumps or by gravity.
Proper handling of biosolids
The waste sludge from the final clarifiers, along with the sludge from the primary clarifiers, is pumped to three gravity thickeners. The purpose of these gravity thickeners is to thicken the sludge in order to avoid excess water from entering the digesters.
The sludge from the gravity thickeners is pumped to two primary digesters. The primary digesters are part of an anaerobic digestion process, involving a biological treatment method in which organisms break down and reduce the organic material of the solids to methane, carbon dioxide and other gases, as well as water and inorganic solids that will further reduce decomposition upon its final disposal.
For proper digestion, the temperature in these digesters has to be maintained between 80 and 100 degrees Fahrenheit throughout the year. During this process, enough methane is produced and used as a fuel for the boiler to heat the sludge to the desired temperature. After proper digestion, the sludge is sent to three secondary digestors. The purpose of these secondary digesters is to separate any excess water from the sludge and hold it prior to sludge dewatering.
The sludge dewatering process consists of four belt filter presses. During this process, the liquid sludge is converted to a solid sludge by the belt filter presses. The solids from the belt filter presses are called biosolids.
The biosolids from the belt filter presses are trucked to the shed at the Rocky Creek Water Reclamation Facility. These solids from Lower Poplar are mixed with the Rocky Creek Plant's solids and sent to farm land throughout the surrounding area. Farmers benefit from the productive use of the nutrients in the solids. These solids are applied in a controlled manner and analyzed regularly for chemical and biological content.
See more information on the MWA's Biosolids Recycling Program
The Rocky Creek Water Reclamation Facility (WRF)
The Rocky Creek Water Reclamation Facility (WRF) provides wastewater treatment for the southern and western portions of the City of Macon and Bibb County. The facility was built in the early 1970's as a joint treatment facility with the Macon Kraft Company, now called Graphic Packaging, Inc.
The current design flow of the plant is for handling a monthly average of 24 million gallons of wastewater per day (MGD) or a weekly average of 30 MGD. The current treatment flow is approximately 18.5 MGD, with 7 to 9 MGD coming from the Graphic Packaging industrial site.
The Rocky Creek Plant is an advanced secondary wastewater treatment facility utilizing the extended aeration activated sludge process, followed by conventional filtration.
There are three separate flow streams conveying wastewater to the plant – the Graphic Packaging, Tobesofkee Creek and Rocky Creek sewer interceptor lines. Sewage from the Rocky Creek and Tobesofkee interceptors flow by gravity to the plant through two influent barscreens and then to the influent pumping station. The influent pumping station consists of four pumps that pump a total of 14 million gallons of wastewater per day (MGD). The wastewater is then pumped through two grit structures whose purpose is to remove any sand or coarse debris.
The secondary treatment of wastewater at the Rocky Creek facility begins with its three aeration basins. The Graphic Packaging wastewater flows through two of those aeration basins, each with a 7 million gallon capacity. The Rocky Creek wastewater flows through the third basin, which can handle up to 14 million gallons.
Flow from the aeration basins is split between six circular final clarifiers. Three are used to handle the Graphic Packaging wastewater, and the other three take care of the Rocky Creek wastewater.
The effluent from the clarifiers is then sent to the post aeration/chlorine contact chambers where chlorine is added for disinfection purposes. A portion of the effluent is pumped to eight individual sand filters, where the treated wastewater is used for several purposes at the plant, including dewatering wash down, chlorine injection, etc.
After chlorine is added and allowed enough contact time for sufficient kill of pathogens, the effluent is de-chlorinated by chemical sodium bisulfate, prior to sending the water to the Ocmulgee River. The plant effluent flows by gravity to the river. The effluent pumping station serves the purpose of pumping the effluent when high river levels prevent gravity flow.
Waste sludge produced during the wastewater treatment process is pumped to three gravity thickeners. The purpose of the gravity thickeners is to enhance the thickness of the sludge prior to the dewatering process.
Scum from the surface of the final clarifiers is dewatered on the two scum screens and disposed of in a sanitary landfill. The thickened solids from the gravity thickeners are then routed to two holding tanks for storage.
The sludge from the holding tanks is pumped to eight belt filter presses. Polymer is added to the sludge to enhance flocculation. The liquid sludge is converted to a solid sludge by the belt filter presses. The solids from the belt filter presses are called biosolids.
These biosolids from the Rocky Creek Facility are placed under a shed and mixed with the solids that have come from the Lower Poplar WRF. Macon Soils is a subsidiary of the MWA that handles the final disposal of biosolids from the Authority's two wastewater treatment plants. Trucks from Macon Soils take the biosolids from the shed and apply it on the land of farmers in Bibb and surrounding counties. The farmers benefit from these biosolids because of their nutrient content.