The Richmond Sanitary District welcomes you to its wastewater treatment facility. The Clean Water Act of 1972 and subsequent federal and state regulations have mandated all communities to protect our environment by discharging treated wastewater into our rivers and streams that meets the highest standards of water quality.In the face of the present requirements of environmental protection, the Richmond Sanitary District continues to operate it’s facility with the continuing commitment to its mission to abate pollution and ultimately safeguard public health through it’s services of reclamation, recycling and disposal of the community’s waste in accordance with applicable statutes.The Sanitary District covers approximately 20+ square miles within the City of Richmond and Wayne County, Indiana. The operation and control of the many steps in the wastewater treatment process are monitored from the control room located in the Intermediate Pump Building. The entire treatment facility is under the constant monitoring and control of a team of state certified operators. RSD’s management continues to upgrade the plant’s SCADA computer system for efficiency in process control and 24-hour monitoring and alarming.  The laboratory is the quality control center for the facility. It’s staff tests samples from the various stages of treatment to monitor the effectiveness of each step in the treatment process. It also monitors the output from the many industries in the Richmond area, as well as the treatment plants’ output.

Preliminary Treatment

On a normal day, ten million gallons or more of untreated wastewater flows through the 3 main interceptors into the newly constructed headwork’s facility (2005) of the treatment plant. The influent is composed of approximately 20% industrial and 80% residential waste. Wastewater entering the plant goes through several initial steps to separate the wastewater from settleable solid materials. On a daily basis, each person contributes about 200 gallons of wastewater to this system.

 

Once the wastewater reaches the treatment facility, two step screens remove objects that could plug or harm the pipes, pumps and the efficiency of treatment downstream. Trash, sticks, other inorganic and organic material is removed from the wastewater. The debris is compacted and washed before being dumped into carts, which are then transported to the landfill for disposal.

 

The wastewater then flows into 2 “pista grit” grit removal tank systems. The circular design of the tanks and direction of the paddles pushes the heavier grit to the bottom of the tanks and floats the lighter organic material out of the tanks to the primary wetwell.

Two grit pumps take the accumulated grit out of the tanks and passes through the grit washer system. The grit undergoes washing and dewatering and it disposed of at the landfill.

 

The wastewater flow is measured through one or both of the 3’parshall flumes. Changes in influent flow rates affect the hydraulics of all treatment processes, such as detention time, surface loading, and weir overflow rate, all of which will affect the efficiency of treatment.

 

The wastewater suspension is gravity fed into the seven rectangular primary clarifiers (upgraded 2005, 96’x16’x13’) and pumped into the (75’x16’) four circular primary clarifiers. These tanks are called primary clarifiers because they are the first clarifiers in the process. Here, mostly organic solids settle into hoppers in the bottom of the clarifiers for periodic pumping to the mix tank/thickener system before being pumped to the digesters. Greases and other floatable material floats on top of the water and is skimmed off and removed through the outlet end of the clarifiers and directed to a scum well for dewatering and disposal.

 

Scum consists of grease and other floatable material. The floating solids that are removed from tanks during the treatment process by gravity or pumping, are directed to the scum equalization tank for processing. A newly constructed scum and grease building (2005) house two grease reactors and a scum dewatering system called a “rotomat scum drum”.

 

The floating solids pass through the scum drum, which is a slotted drum that rotates.

Hot water and scrappers clean the drum slots and surface area of the drum during the dewatering process. The scum is dewatered, compacted and drops into an auger and disposed in the landfill.

 

Grease from restaurants is hauled to our facility for processing from the surrounding three states. Grease that enters the sewer system pipes creates many problems for the collection and wastewater treatment facility. Two rectangular-shaped tanks receive grease for processing. Air is supplied to these tanks for mixing and air requirements for aerobic digestion process. The grease is periodically pumped out and treated through the downstream processes.

 

Wastewater treatment is the establishment of a favorable environment which does nature’s work in a time frame controlled by people. This is a natural biological process.

The roughing towers play an important role in the treatment of wastewater. A portion of the suspension from the circular primaries flows by gravity to one of the two 90’ x 30’ high towers. Aerobic bacteria are grown on the plastic media cells installed in the towers. The rotating distributor arms spread the wastewater evenly across the top of the media. The water trickles downward, crossing million of square feet of media surface. These microorganisms eat the carbon compounds and reduce these compounds from a 4:1 ratio to a 1:1 ratio compared to nitrogen compounds. When the wastewater is returned to the aeration tanks, this reduced available carbon drives the microorganisms to use ammonia-based materials as their source of growth energy. This helps the treatment process meet the standards for ammonia discharge in the final effluent.

 

The effluent from the roughing towers flow to the seven intermediate clarifiers. They provide a zone of settling to remove any biomass and old bacteria that is continuously being flushed from the roughing towers. Three circular intermediate tanks 50’x10’, and four rectangular intermediate tanks 96’x20’x12’.

 

The aeration banks are the heart of the wastewater treatment. There are 27 tanks arranged in 9 banksof 3(60’x30’x16’) tanks each. Air is supplied to the tanks by large electric blowers, which the aerobic microorganisms require in order to sustain life. The supplied air creates an environment to accelerate the growth of the organism, thus increasing their need for food. Many varieties of aerobic microorganisms digest the organic material; both dissolved and suspended material reducing the biochemical oxygen demand and ammonia removal. The wastewater from the roughing towers contains reduced available carbon and drives the microorganisms to use ammonia-based materials as their source of growth energy. This helps the treatment process meet the standards for ammonia discharge in the final effluent. This is called activated sludge process.

 

Alum, a coagulant, is added to the aeration effluent. This promotes the sticking of particles and forms larger masses, which then settles out in the final clarifiers. Within the masses, phosphorus is contained. This helps us meet our phosphorus removal limitations. A portion of this settled activated sludge ends up in the digesters, and on farmland as fertilizer

 

The four final clarifiers (105’x14’) are the last stage in the separation process. The effluent from the aeration tanks now is made up of bacteria and sludge webbed together to form a floc that settles. The four final clarifiers use gravity to separate the floc from the treated water by recirculating the microorganisms (activated sludge) back into the aeration tank system. A balance of Food to Microorganism (F:M) ration is required for successful treatment. The portion of activated sludge not needed is wasted to the mix tank/thickener tank process.

 

Tertiary Treatment

Effluent from the four final clarifiers is pumped to the eight tertiary filter cells. These cells contain approximately 3’ – 4’ of a small gravel media mixture. The water enters the trough in the middle of the cell and water flows by gravity through the gravel media filtering out the remaining particles in the wastewater.

 

When the gravel media is so dirty, the tank is taken out of service and backwashed. Water and air is pushed back up through the media to clean it, and is captured in the mudwell and pumped to the mix tank/thickener system. The cell is then put back in service after the backwash process is completed.

 

The Richmond Sanitary District’s Wastewater Treatment Facility discharges into the east fork of the Whitewater River. The river flows directly into the Brookville Reservoir, an important area recreational lake. Chlorination and a final aeration assure that the water released into the river is safe for human body contact. Chlorination is used to provide disinfection to the treated wastewater before it leaves the treatment plant April 1 through October 31. Sulfur dioxide is added to remove the chlorine residual. The wastewater must be disinfected to reduce or eliminate the pathogenic bacteria commonly found in wastewater.

 

The effluent then leaves the treatment plant through the cascade aerator. A bowl-shaped structure with cascading steps causes the water to capture oxygen before it blends with the river. The Richmond Sanitary District monitors the effluent not only for its impact on future human consumption, but also for the impact on the environment itself. The sparkling clear water released from the cascade represents the useful blending of nature and technology.

 

The mix tank receives the sludge drawn off the primary, intermediate, and final clarifiers, mudwell debris and waste activated sludge. The mix tank does what its name refers; it mixes all the contents for a complete mixture. The mixture flows into two thickener tanks. These thickener tanks dewater the sludge by letting the sludge settle to the cone-shaped bottom and is then pumped to the primary digesters. The dewatering process helps save room in the digesters and the cost of heating.

 

During the process of treating wastewater, bacteria digest much of the organic matter as it moves through the system. However, at almost every stage of the process, a certain amount of sludge collects at the bottom of the many components of the system. Personnel at the wastewater treatment plant work closely with an agronomist and the sludge hauling company to determine the loading rate of the field receiving sludge. Sludge samples are sent to an independent laboratory for analysis to determine if the sludge meets state and federal regulations. Every soil has its own loading rate; its own unique capacity to absorb and/or release the nutrients of sludge and the heavy metals. This is monitored very carefully when sludge is distributed over area fields. Biosolids contain three major nutrients for crop growth and performance. These nutrients are nitrogen, phosphorus, and potassium. When properly applied, biosolids helps the farmers increase the yield of crops such as corn, oats and soybeans. The humus-like quality of this product makes it an excellent soil conditioner. While renewing the soil it enhances plant growth.

 

Sludge from the gravity thickeners is first pumped into the “primary digesters” (95’x26’). Here the sludge is mixed and heated to temperatures 90-100 F. This promotes anaerobic (does not need free oxygen) bacteria and it “eats” the sludge and helps to stabilize it. The bacteria breaks down the sludge particles and some of the by-products are water, methane, hydrogen sulfide, and carbon dioxide. About 95% of the digestion process takes place here. These digesters are mixed to keep the bacteria in contact with the new incoming sludge.

 

This heated sludge is then pumped to one of the two “secondary” digesters where it can just rest with no heat or mixing. In secondary digesters the solids again settle to the bottom and the liquid goes to the top. The liquid (supernatant) is sent back to the front of the plant via pipes to be reprocessed. The bacteria then die, leaving behind a humus type of fertilizer that is applied to local farmland.

 

Working to ensure water quality is important for people and wildlife. In fact, the water quality standards for water discharged into the river are often determined by the needs of the wildlife versus the needs of people. One of the projects designed to assist wildlife is visible when entering the Richmond facility. Near the Whitewater River, a wetland was constructed in Spring 1997 to replace one that was destroyed at the landfill. It is now part of federal law that if one acre of wetland is eliminated, it must be replaced by two acres at a different location. Since the landfill destroyed a small wetland while constructing a new cell for burying trash, a new wetland was created. This new wetland is about 1.6 acres in size and is fed by water discharged from the wastewater treatment plant. It has an average depth of 18 inches, with some deeper spots of 3 feet. A variety of birds, insects and other animals have been spotted. Muskrats have built small lodges in several locations. Trees fell by beavers have also been located.