Secondary wastewater treatment is the second stage of wastewater treatment. Primary treatment eliminates suspended solids, colloidal particles, oil, and grease.
Secondary treatment is the biological treatment of wastewater to remove any organic matter present. This treatment is accomplished by indigenous and aquatic microorganisms, such as bacteria and protozoa digesting biodegradable soluble contaminants, such as sugar, fat, detergent, and food waste. These processes are temperature sensitive, and the rate of biological reactions increases, as the temperature rises.
Which is most used technology for secondary sewage treatment?
Secondary wastewater treatment is divided into two distinct processes:
1. Aerobic waste?water treatment is a biological treatment that employs oxygen, to break down organic materials and remove other contaminants, such as nitrogen and phosphorus. Aerobic treatment technologies include the following:
1. Extended Aeration System (EAS)
2. Activated Sludge Process (ASP)
3. Sequential Batch Reactor (SBR)
4. Membrane Bioreactor (MBR)
5. Moving Bed Bio Film Reactor (MBBR)
2. Anaerobic treatment is a procedure in which microorganisms break down wastewater or materials, without the use of dissolved oxygen. However, anaerobic bacteria may and will use the oxygen found in the oxides injected into the system, as well as organic material in the effluent. Up-flow Anaerobic Sludge Blanket Reactor (UASB) is an anaerobic treatment technology.
Activated Sludge Process/Extended Aeration System
· The Extended Aeration process design and mixing regime are comparable, to those of the entirely mixed process.
· Low organic loading, lengthy aeration period, high MLSS concentration, and low F/M are all used in the process.
· The effectiveness of BOD elimination is excellent.
· Because, of the long detention time in the aeration tank, the mixed liquor solids experience significant endogenous respiration, and become well stabilized.
· The increased oxygen need has an effect on the system's total operating cost.
· The elimination of primary settling and separate sludge digestion, however, simplifies the procedure.
Sequential Batch Reactor (SBR)
· The Sequential Batch Reactor is a fill and draw device for wastewater treatment, which uses activated sludge.
· A single batch reactor can perform equalization, aeration, and clarification. SBR systems are effective for big industrial effluents.
· Although, SBR requires more maintenance in operation due to the PLC-based process, it is more efficient and requires less space for the STP or ETP.
· SBR combines the secondary treatment and settlement processes.
· It is used to decrease organic matter (BOD and COD) by bubbling oxygen, through a mixture of wastewater and activated sludge.
· Following treatment, the treated water can be discharged into surface water.
Moving Bed Biofilm Reactor (MBBR)
A Moving Bed Biofilm Reactor (MBBR) is made up of an aeration tank, which is comparable to an activated sludge tank, and unique plastic carriers that provide a larger surface area for biofilm growth.
Membrane Bioreactor (MBR)
The membrane bioreactor (MBR) is a hybrid of ultrafiltration (UF) and the activated sludge process. MBR generates high-quality effluent that can be discharged to surface water for reuse. It can be retrofitted to existing systems.
Up-flow Anaerobic Sludge Blanket Reactor (UASB)
· UASB technology is a type of anaerobic digester.
· The UASB reactor is a methane-producing digester that employs an anaerobic process, to generate a blanket of granular sludge, which is then digested by anaerobic microorganisms.
· In the case of larger organic loads, UASB assists in reducing the higher extent of organic loads, and further aerobic treatment for the remaining loads can be undertaken.
· Generally, during UASB reactor treatment, the substrate first travels through an enlarged sludge bed, containing a high concentration of biomass.
· The leftover substrate is then passed through less dense biomass, known as the sludge blanket.
· The sludge recirculation cum disposal pump is used for sludge circulation and mixing. Excess granular sludge is disposed of in sludge drying beds.
How can we assist?
Netsol Water offers a wide range of sophisticated sewage treatment solutions, such as ASP, MBR, MBBR, UASB, SBR, water softeners, RO Plants, etc. We also offer various technologies for secondary sewage treatment.