Sewage Treatment Plants

Membrane Bioreactor (MBR)

The term membrane bioreactor (MBR) defines a combination of an activated sludge process and WW separation by means of membranes.The MBR process was introduced in the late 1960s, as soon as commercial scale ultra filtration (UF) and micro filtration (MF) membranes were available. The original process was introduced by Dorr-Olivier Inc. and combined the use of an activated sludge bioreactor with a cross flow membrane filtration loop, see Figure 1. The flat sheet membranes used in this process were polymeric and featured pore sizes ranging from 0.003 to 0.01 μm.
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Sequential Batch Reactor (SBR)

The Sequencing Batch Reactor (SBR) is an activated sludge process designed to operate in a batch mode with aeration and sludge settlement both occurring in the same tank. Difference between SBR and activated sludge system is that the SBR tank carries out the functions of equalization, aeration and sedimentation in a time sequence.

An appropriately designed SBR process is a unique combination of equipment and software. Working with automated control reduces the number of operator skill and attention requirement. There are basically five stages to treatment: Fill, React, Settle, Decant and Idle.

Aeration times vary according to the plant size and the composition/quantity of the incoming liquor. The settling stage is usually the same length in time as the aeration. The sludge is allowed to settle until clear water is on the top 20%-30% of the tank volume. The decanting stage most commonly involves the slow lowering of a scoop or “trough” into the basin. SBR is ideally suited when nitrification, denitrification and biological phosphorus removal is necessary.
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Moving Bed Bioreactor (MBBR)

MBBR is an improved version of Fixed Film Bio Reactor like SAFF (Surface Area Fixed Filmed Technology (SAFF) or Rotating Bio Reactor (RBC), with a difference of MBBR carrier media is free floating in the Sewage/Effluent. MBBR technology employs thousands of polyethylene biofilm carriers operating in mixed motion within an aerated wastewater treatment basin.
A Moving Bed Biofilm MBBR reactor consists of a tank with submerged but floating plastic (usually HDPE, polyethylene or polypropylene) media having specific gravity less than 1.0. The large surface area of the plastics provide abundant surface for bacterial growth. Biomass grows on the surface as a thin film whose thickness usually varies between 50-300 microns. Each individual bio carrier increases productivity through providing protected surface area to support the growth of heterotrophic and autotrophic bacteria within its cells. It is this high-density population of bacteria that achieves high-rate biodegradation within the system, while also offering process reliability and ease of operation. Medium or coarse bubble diffusers uniformly placed at the bottom of the reactor maintains a dissolved oxygen (DO) concentration of > 2.5-3 mg/L for BOD removal. Still higher DO concentrations are maintained for nitrification. To retain the media flowing out of the tank, screens are placed on the downstream walls. A clarifier or a DAF is placed downstream of the MBBR tank to separate the biomass and the solids from the wastewater. No sludge recycle is required for this process. A typical MBR Media is shown below.
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Packaged Sewage Treatment Plants

Package plants are used in rural areas, highway rest stops and trailer parks where population to be served ranges from 10 – 100 people or so.
One type of system that combines secondary treatment and settlement is the cyclic activated sludge. Typically, activated sludge is mixed with raw incoming sewage, and aerated. The settled sludge is run off and re-aerated before a proportion is returned to the head works. The disadvantage of the process is that it requires a precise control of timing, mixing and aeration. This precision is typically achieved with computer controls linked to sensors. Such a complex, fragile system is unsuited to places where controls may be unreliable, poorly maintained, or where the power supply may be intermittent.SBR plants are now being deployed in many parts of the world.
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Submerged Aerobic Fixed Film Reactor

Submerged Aerobic Fixed Film Reactor (SAFF) is a cost-effective method of waste water treatment and sewage sanitation that is primarily used in residential and commercial complexes. This technology primarily has on the three stages that are Primary Settlement, Secondary Treatment and Final Settlement / Clarification.
In the wastewater industry, SAFF Technology is seen as the simple and cost effective method of commercial and residential sewage sanitation / waste water treatment, particularly for small to medium sized treatment plants where available land is limited, and where full time operational manning would be uneconomical. A well designed Submerged Aerated Filter plant has no moving parts within its process zones, any serviceable items will be positioned to access easily without disrupting the ongoing treatment.
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Rotating Biological Contactor

  • Introduction:
    Water is the most important natural gift for human being and aquatic life. Due to continuous technological growth and industrialization, the water has been fully polluted and categorized as water pollution. The outlet water of industries and human which accedes the limit of organic and inorganic components in the water is called wastewater (polluted water).
  • Sources of Waste Water:
  • Characteristics of Waste Water:
    Physical Characteristics
    Chemical Characteristics
    Biological Characteristics

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Extended Aeration Treatment Packages

Extended Aeration treatment system works by providing ideal conditions for aerobic bacteria and other micro-organisms; these micro-organisms then decompose the biological contaminants in the raw sewage.
The treatment plant provides the proper environment, sufficient oxygen and other elements which allow the bacteria to consume the organic matter and to live and multiply within the treatment plant. In this way the aerobic bacteria and microbes decompose the sewage and waste to a stable form – odor and nuisance free.
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Grey Water Treatement System

What is Grey water?
Grey water can be defined as any domestic wastewater produced, excluding sewage. The main difference between grey water and sewage (or black water) is the organic loading. Sewage has a much larger organic loading compared to grey water.

Some people also categorise kitchen wastewater as black water because it has quite a high organic loading relative to other sources of wastewater such as bath water.

People are now waking up to the benefits of grey water re-use, and the term “Wastewater” is in many respects a misnomer. Maybe a more appropriate term for this water would be “Used Water”.
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Anaerobic Systems

Anaerobic treatment differs from conventional aerobic treatment in that no aeration is applied. The absence of oxygen leads to controlled anaerobic conversions of organic pollutants to carbondioxide and methane, the latter of which can be utilized as energy source.

The main advantages of anaerobic treatment are the very high loading rates that can be applied (10 to 20 times as high as in conventional activated sludge treatment) and the very low operating costs. Anaerobic treatment often is very cost-effective in reducing discharge levies combined with the production of reusable energy in the form of biogas. Pay-back times of significant investments in anaerobic treatment technologies can be as low as two years. Anaerobic treatment of domestic wastewater can also be very interesting and cost-effective in countries were the priority in discharge control is in removal of organic pollutants.
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Sludge Conditioning Systems

Sludge conditioning is a process whereby sludge solids are treated with chemicals or various other means to prepare the sludge for dewatering processes
Chemical Conditioning: Chemical conditioning (sludge conditioning) prepares the sludge for better and more economical treatment with vacuum filters or centrifuges. Many chemicals have been used such as sulfuric acid, alum, chlorinated copperas, ferrous sulfate, and ferric chloride with or without lime, and others.
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Thermal Drying Systems

Thermal Drying of Wastewater Solids:Thermal drying is one of the technologies available for processing of solids produced at municipal wastewater treatment plants (WWTPs). Thermal drying technology, although originally developed for material and chemical processing applications, has been successfully applied to WWTP solids and, thus, it is a viable and proven solids processing technology primarily aimed at producing a marketable product.
Thermal drying technology is based on removal of water from dewatered solids which accomplishes both volume and weight reduction. The added benefit of thermal drying is that it typically results in a product with significant nutrient value. Typically, dewatered solids (at approximately 18% to 35% dry solids content) are delivered to a thermal drying system, where most of the water is removed via evaporation resulting in a product containing approximately 90% solids. In the thermal drying system, the temperature of the wet solids mass is raised so that the water is driven off as a vapor. By removing most of the water from the solids, thermal drying results in a significant reduction in both volume and mass..
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