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What is Sewage ?
Sewage is a mixture of domestic and industrial wastes containing 99% water, but the remainder contains some ions, suspended solids, toxic chemicals and harmful bacteria that must be removed before releasing of water into the sea.
Sewage contains organic impurities such as BOD, COD which cause bad smell and contains harmful gases. If it is not treated properly than it will lead to many irreversible problems for human & other living things.
Why Sewage treatment is necessary?
Sewage is a resource that can be recycled for various uses like gardening, toilet flushing, car wash, cooling towers. Faced with the alarming fact that over 60% of the sewage generated in our country goes untreated, with its negative impact on human health, the government is focusing on waste management through centralized sewage treatment plants and by mandating large upcoming real estate projects to have their own treatment facility.
Sewage Treatment is essential to ensure that the receiving water into which the effluent is ultimately discharged is not significantly polluted. It works on producing environmentally safe fluid waste stream and a solid waste suitable for disposal or reuse.
Excel Filtration Pvt. Ltd (EFPL) approach is to see wastewater as an opportunity, not a burden.
EFPL Flow Diagram Process Description
Flow Diagram of Effluent Treatment Plant
Process Description of Sewage Treatment Plant
Sewage treatment involves:
It involves the process of removing contaminants from wastewater and household sewage, both effluents and domestic. It includes physical, chemical and biological process to remove physical, chemical and biological contaminants. The objective of sewage treatment is to produce a disposable effluent without causing harm to the surrounding environment and prevent pollution.
Sources of waste water:
Sewage treatment generally is divided into several stages:
Large solids (i.e. those with a diameter of more than 2cm) and grit (heavy solids) are removed by screening. These are disposed of in landfills.
2) Primary Treatment:
Primary treatment removes materials that can be easily collected from the raw sewage before they damage or clog the pumps and sewage limits of primary treatment clarifiers trash, tree, limbs, leaves, branches etc. Here settled and floating materials are scrapped off and the remaining liquid discharged and subjected to secondary effluent.
3) Secondary or Biological Treatment:
Secondary treatment removes dissolved and suspended biological matter. It is typically perform by indigenous, water-borne micro-organisms in a managed habitat. It requires separation process to remove microorganisms from the treated water before its discharge or tertiary treatment.
4) Tertiary Treatment:
Tertiary treatment is to provide a final treatment stage to raise the effluent quality before it is discharged to the receiving environment (sea, river, lake, ground etc). This is a final process and also called effluent polishing."
We adopt todayÂ technology developments that allow us to realize the vision and offer advanced wastewater treatment process. Different technologies are mentioned below:
Activated Sludge Process (ASP)
ASP is most commonly used suspended growth aerobic process. In this process, organic matter present in the wastewater is aerated so that micro-organisms metabolize the soluble and suspended organic matter. Part of the organic matter is synthesized and form new cells and part is oxidized into CO2 and water to derive energy. The new cells formed are removed in the settling tanks and part of this settled biomass is returned to the aeration tank while the remaining is removed as excess sludge.
Integrated Fixed Film Activated Sludge (IFAS)/ Moving Bed Bio-Reactor (MBBR)
MBBR technology works on the principle of attached growth system and uses rotating bio media to retain an active biomass to reduce the influent BOD Levels.
MBBR configuration combines biofilm and activated sludge systems for retrofitting existing plants for biological (TN) and total phosphorus (TP) removal. It tends to increasing plant capacity and improving effluent quality.
Provides BOD removal with a very short hydraulic retention time (HRT).Â Fine Bubble diffusers are used with the MBBR media in suspension (specific gravity < water) giving a good air dispersal and low level of blockage due to growth of biological film.
1) Elimination of plugging.
2) Design and implementation efficiencies ensure lower capital and operation costs than conventional alternatives.
3) Simple media addition allows for easy plant expansion to accommodate population growth or other needs for capacity.
Sequential Batch Reactor (SBR)
The SBR processes save more than 60% of the cost required for conventional activated sludge process in operating cost and also achieve high effluent quality in a very short cycle. Sequencing Batch Reactor (SBR) is an activated sludge process designed to operate under non-steady state conditions.
The sequential batch reactor (SBR) process is a fill and draw type activated sludge process where individual reactors are filled one by one in five discrete periods i.e. Fill, React, Settle, Decant and Idle/ Waste Sludge.
1) Better resistance to sludge bulking than other types of activated sludge systems.
2) No need of external clarifiers.
3) Can retrofit existing tanks, basins and ponds.
4) Greater ability to meet effluent limitations (organic and nutrient) than other types of activated sludge wastes/ Wastewater treatment systems.
Membrane Bio Reactor
MBR technology combines biological activated sludge process with physical separation treatment using membranes which are submerged in the tank (instead of secondary clarifier). This technology has become more popular, abundant, accepted in recent years for treatment of different types of waste waters. This technology improvises overall operational effectiveness and reduces space requirement.
Membrane is made of cost-effective non-woven fibrous material. It has many outstanding properties, such as controllable pore sizes and easy fabrication of the membrane module to achieve the desired surface area.
Combined treatment consists of combining several stages of treatment in package units called membrane bioreactors (MBRs).
1) High Effluent Quality
2) High loading rate capacity
3) Easy operable
4) Fully automatic
5) Allows for plant expansion in the same footprint
Â Up flow Anaerobic Sludge Blanket Reactor(UASB)
This process includes anaerobic treatment is carried out in absence of oxygen/air which leads to conversion of organic matters into CH4 and end products like CO2 and NH3. This system uses granulated bacteria which are contacted to organic components present in the wastewater. Methane gas is also produced due to decomposition of organic components.
It is suitable for high strength waste water and also use for domestic sewage in warm climates. The process takes place into two zones.
1. Reactor zone
2. Settling zone