Table of Contents
Secondary treatment removes the soluble organic matter that escapes primary treatment. It also removes more of the suspended solids. Removal is usually accomplished by biological processes in which microbes consume the organic impurities as food, converting them into carbon dioxide, water, and energy…
What does secondary wastewater treatment do?
Secondary treatment is a treatment process for wastewater (or sewage) to achieve a certain degree of effluent quality by using a sewage treatment plant with physical phase separation to remove settleable solids and a biological process to remove dissolved and suspended organic compounds.
What is meant by secondary treatment?
Secondary treatment is the second step in most waste treatment systems during which bacteria consume the organic parts of the wastes. This is accomplished by bringing the sewage, bacteria and oxygen together in trickling filters or within an activated sludge process.
What do aerobic bacteria do in sewage treatment?
Oxygen is continuously mixed into the wastewater or sewage by a mechanical aeration device, such as an air blower or compressor. Aerobic microorganisms then feed on the wastewater’s organic matter, converting it into carbon dioxide and biomass which can be removed.
How much Bod does secondary treatment remove?
The clarifiers can effectively remove 50 to 60 percent of the suspended solids and 25 to 40 percent of the BOD (Biochemical Oxygen Demand) from the waste water.
Why is BOD reduced in secondary sewage treatment?
The bacteria also require a carbon food source for energy and conversion of nitrogen. The bacteria metabolize the carbonaceous material or BOD in the wastewater as this food source, metabolizing it to carbon dioxide. This in turn reduces the BOD of the sewage, which is desirable.
What does a secondary clarifier remove?
Filtration: Physical / Chemical. Wastewater leaving the Secondary Clarifiers looks as clean as drinking water! The filters remove very tiny solids (“suspended solids”) from the wastewater before it moves on to disinfection.
What Cannot be removed from wastewater?
#1 – Pharmaceuticals and Personal Care Products (PPCPs) Both prescription and over-the-counter medications and supplements are wreaking havoc on wastewater. Even if people dispose of their unused medications correctly, some of those medications make their way into the urine stream.
What does secondary treatment not remove?
Secondary treatment removes the soluble organic matter that escapes primary treatment. It also removes more of the suspended solids. Removal is usually accomplished by biological processes in which microbes consume the organic impurities as food, converting them into carbon dioxide, water, and energy…
How do I increase bacteria in my aeration tank?
Add fixed-film media to the aeration tank environment to increase the biomass concentration. Place additional aeration tanks into service to adequately process organic loadings. aeration tank has properly performed its function. The focus now moves towards separating the bacteria from the clean water in the clarifier.
What bacteria is used to treat sewage?
Bacillus is an excellent treatment of bacteria in wastewater but is best suited for treating fats, oils, greases, and proteins. That is why they are primarily used in wastewater treatment plants.
What is the last stage of the sewage treatment?
Tertiary Treatment The purpose of this final stage is to further improve the quality of the water before it is released and reused in the environment for lakes, rivers, seas or other places.
What is the difference between primary and secondary clarifiers?
The primary clarifier is designed to dispose of inorganic solids floating at the surface. It also tackles solids settling at the bottom. In the secondary clarifier, 100 percent or nearly 100 percent of the sludge, is organic. In this clarifier, the sludge is compact-ready and significantly denser.
What is the main process in secondary sewage treatment?
Secondary treatment removes nutrients and remaining solids through bacterial decomposition. This treatment uses naturally occurring biological processes. The level of oxygen in the wastewater is changed at different stages – to produce aerobic and anaerobic environments.
How do secondary clarifiers work?
In the activation process, secondary clarifier tanks and aeration basins are interdependent units. The wastewater-sludge mixture flows from the aeration basins into the secondary clarifier where the sludge settles and is conveyed back to the aeration basins via the return sludge pumping station.
Which is used in secondary treatment of sewage water?
SBR combines the secondary treatment process and settlement. It is used to reduce the organic matter (BOD and COD), oxygen is bubbled with a mixture of wastewater and activated sludge. After this treatment, the treated water can be discharged on surface water.
Why secondary treatment is known as biological treatment?
2. Secondary treatment of wastewater works on a deeper level than primary level. It is called as biological treatment because it is designed to substantially degrade the biological content of the waste through aerobic biological processes. This step removes the dissolved organic matter by the use of biological agents.
What are the 3 stages of wastewater treatment?
There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment.
What is secondary waste?
Secondary waste is waste generated from different sources and of different nature, i.e. waste generated in a process that is known as a waste treatment operation; it includes residual materials originating from recovery and disposal operations, such as incineration and composting residues.
What happens to the main part of activated sludge during secondary treatment?
After secondary treatment a part of activated sludge is passes back to aeration tank as inoculum while most of the part of activated sludge passed to anaerobic sludge digesters.
What is the difference between primary and secondary wastewater treatment?
The main difference is the way each respective treatment is processed. Primary treatment works on sedimentation, where solids separate from the water through several different tanks. In contrast, secondary treatment uses aeration, biofiltration and the interaction of waste throughout its process.
What is the role of microbes in secondary treatment of sewage?
These microbes use the organic matter present in wastewater and reduce the BOD (Biological oxygen demand) which is the amount of oxygen consumed by bacteria when one litre of organic matter is oxidised by them. This effluent is then passed into the settling tank.
What is primary and secondary treatment for sewage?
There are two basic stages in the treat- ment of wastes, primary and secondary, which are outlined here. In the primary stage, solids are allowed to settle and removed from wastewater. The secondary stage uses biological processes to further purify wastewater. Sometimes, these stages are combined into one operation.
How an aerobic bacteria are beneficial in secondary sewage treatment?
Aerobic bacteria use oxygen, which is added mechanically, to break down wastewater contaminants, converting it into energy. Bacteria use this energy to grow and reproduce.
What does tertiary treatment remove?
Tertiary treatment is the final cleaning process that improves wastewater quality before it is reused, recycled or discharged to the environment. The treatment removes remaining inorganic compounds, and substances, such as the nitrogen and phosphorus.
