Wastewater treated by primary treatment + wastewater treated by secondary treatment + wastewater treated by tertiary treatment + wastewater discharged without treatment have to add up to 100% of wastewater generated. Volumes should only be accounted for under the highest treatment category to which they were subjected.
Full Answer
What is the primary level of treatment in wastewater treatment?
Typical Urban Wastewater Treatment Plant The primary level of treatment uses screens and settling tanks to remove the majority of solids. This step is extremely important, because solids make up approximately 35 percent of the pollutants that must be removed.
What are the different levels of treatment at backriver?
Wastewater to the BackRiver Wastewater Treatment Plant currently receives four levels of treatment: Preliminary, Primary, Secondary, and Tertiary. The preliminary treatment process includes six fine screens (one quarter inch openings) and four grit removal basins.
How is wastewater treated in a wastewater treatment plant?
In this treatment plant, wastewater first undergoes primary and secondary treatment. For the tertiary treatment, the BNR process occurs in the bioreactors. The BNR process uses bacteria in different conditions in several tanks, to digest the contaminants in the water.
What is final testing in the wastewater treatment process?
Although testing is continuous throughout the wastewater treatment process to ensure optimal water flow, clarification and aeration, final testing is done to make sure the effluent leaving the plant meets permit specifications. Plants that don`t meet permit discharge levels are subject to fines and possible incarceration of the operator in charge.
What are the stages of wastewater treatment?
What Are the Three Stages of Wastewater Treatment? There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment. In some applications, more advanced treatment is required, known as quaternary water treatment.
Where is wastewater held?
During primary treatment, wastewater is temporarily held in a settling tank where heavier solids sink to the bottom while lighter solids float to the surface. Once settled, these materials are held back while the remaining liquid is discharged or moved through to the more rigorous secondary phase of wastewater treatment.
What is the process of removing sediment from a wastewater system?
1. Biofiltration. Bio filtration uses sand filters, contact filters or trickling filters to ensure that any additional sediment is removed from the wastewater. 2. Aeration. Aeration is a lengthy process which increases oxygen saturation by introducing air to wastewater.
What is tertiary treatment?
In the case of water treated by municipalities, tertiary treatment also involves the removal of pathogens, which ensures that water is safe for drinking purposes.
Why is chlorinated water added to filtration?
Chlorine solution is added at the influent of the filtration process for the purpose of minimizing algae growth on the filter beds , and as the primary point of chlorination for disinfection of the plant effluent. Chlorine can also be added downstream of the filtration process for final trim dosing.
Can ferric chloride be added to back river effluent?
To further reduce the phosphorus loading to Back River, ferric chloride and polymer are added separately to the aeration tanks prior to secondary clarification. As an option, polymer can also be added to the effluent after secondary clarification.
What is the process of removing large items from the influent?
Removal of large items from the influent to prevent damage to the facility’s pumps, valves and other equipment .#N#The process of treating and reclaiming water from wastewater (any water that has been used in homes, such as flushing toilets, washing dishes, or bathing, and some water from industrial use and storm sewers) starts with the expectation that after it is treated it will be clean enough to reenter the environment.#N#The quality of the water is dictated by the Environmental Protection Agency (EPA) and the Clean Water Act, and wastewater facilities operate to specified permits by National Pollutant Discharge Elimination System (NPDES). According to the EPA, The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. Under the CWA, EPA sets wastewater standards for industry. The EPA has also developed national water quality criteria recommendations for pollutants in surface waters. EPA's National Pollutant Discharge Elimination System (NPDES) permit program controls discharges.#N#As an example of expected standards, the Biochemical Oxygen Demand (BOD) of average wastewater effluent is 200 mg/L and the effluent after treatment is expected to be >30 mg/L. It is crucial a wastewater facility meets these expectations or risk stiff penalty.#N#The physical process of wastewater treatment begins with screening out large items that have found their way into the sewer system, and if not removed, can damage pumps and impede water flow. A bar screen is usually used to remove large items from the influent and ultimately taken to a landfill.
What happens after a wastewater treatment plant meets all permit specifications?
After meeting all permit specifications, clean water is reintroduced into the environment. Although testing is continuous throughout the wastewater treatment process to ensure optimal water flow, clarification and aeration, final testing is done to make sure the effluent leaving the plant meets permit specifications.
Why is wastewater pumped into a secondary clarifier?
Treated wastewater is pumped into a secondary clarifier to allow any remaining organic sediment to settle out of treated water flow. As the influent exits the aeration process, it flows into a secondary clarifier where, like the primary clarifier, any very small solids (or fines) sink to the bottom of the tank.
What is activated sludge?
These small solids are called activated sludge and consist mostly of active bacteria. Part of this activated sludge is returned to the aeration tank to increase the bacterial concentration, help in propagation, and accelerate the breakdown of organic material. The excess is discarded.
What happens if water flows too slow?
If the water flow is too slow, it impacts the process up stream. The solids that fall to the bottom of the clarifier are know as sludge and pumped out regularly to ensure it doesn’t impact the process of separation. The sludge is then discarded after any water is removed and commonly used as fertilizer.
What is the function of an aeration tank?
The primary function of the aeration tank is to pump oxygen into the tank to encourage the breakdown of any organic material (and the growth of the bacteria), as well as ensure there is enough time for the organic material to be broken down.
Why is chlorine added to water?
Chlorine is added to kill any remaining bacteria in the contact chamber. With the enhanced concentration of bacteria as part of the aeration stage, there is a need to test the outgoing effluent for bacteria presence or absence and to disinfect the water.
What is the purpose of wastewater treatment plants?
Wastewater treatment plants are designed to convert liquid wastes into an acceptable final effluent and to dispose of solids removed or generated during the process. In most cases, treatment is required for both suspended and dissolved contaminants.
What is biological waste treatment?
Various physical methods may be used for the removal of wastewater contaminants that are insoluble in water, such as suspended solids, oil, and grease. Ordinarily, water-soluble contaminants are chemically converted to an insoluble form to allow removal by physical methods. Essentially, biological waste treatment is this conversion ...
How is sludge dewatered?
In this section, sludge is dewatered by the gravity drainage of free water. The gravity drainage zone should increase the solids concentration of the sludge by 5-10%. If the sludge does not drain well in this zone, the sludge can squeeze out from between the belts or the belt mesh can become blinded.
What are the effects of metals on water?
Certain metals are toxic and affect industrial, agricultural, and municipal users of the water source. Metals can cause product quality problems for industrial users. Large quantities of discharged salts necessitate expensive removal by downstream industries using the receiving stream for boiler makeup water.
What is the natural buffering system of a water source?
The natural buffering system of a water source is exhausted by the discharge of acids and alkalies. Aquatic life is affected by the wide swings in pH as well as the destruction of bicarbonate alkalinity levels.
What is the function of oxygen in water?
In a biochemical reaction, dissolved oxygen is consumed as the end products of water and carbon dioxide are formed. Atmospheric oxygen can replenish the dissolved oxygen supply, but only at a slow rate.
Can lagoons be used for biological treatment?
Where organic loads are low and sufficient land area is available, open lagoons may be used for biological treatment. Lagoons provide an ideal habitat for microorganisms. Natural infiltration of oxygen is sufficient for biological oxidation if the organic loading is not too high. However, mechanical aeration (Figure 37-6) is often used to increase the ability to handle a higher loading.
What is the last treatment step before discharge to the Patapsco River?
Tertiary Treatment. Disinfection coupled with follow-up dechlorination is the last treatment step before discharge to the Patapsco River. Chlorine is used at the treatment plant as a disinfectant to destroy disease-causing bacteria and other organisms.
How many tanks are there in a grit facility?
Preliminary treatment includes a Grit facility, which consists of 6 tanks and the usage of mechanically cleaned screens where objects such as rags, sticks, and boards are removed and disposed of in landfills.
Stage One — Bar Screening
Stage Two — Screening
Stage Three — Primary Clarifier
Stage Four — Aeration
Stage Five — Secondary Clarifier
- Treated wastewater is pumped into a secondary clarifier to allow any remaining organic sediment to settle out of treated water flow. As the influent exits the aeration process, it flows into a secondary clarifier where, like the primary clarifier, any very small solids (or fines) sink to the bottom of the tank. These small solids are called activat...
Stage Six — Chlorination
Stage Seven — Water Analysis & Testing
Stage Eight — Effluent Disposal