Extended Aeration/Activated Sludge Process

Extended aeration is a method of sewage treatment using modified activated sludge procedures. It is preferred for relatively small waste loads, where lower operating efficiency is offset by mechanical simplicity.

An Activated Sludge Plant involves:

  1. Wastewater aeration in the presence of a microbial suspension,
  2. Solid-liquid separation following aeration,
  3. Discharge of clarified effluent,
  4. Wasting of excess biomass, and
  5. Return of remaining biomass to the aeration tank.

In activated sludge process wastewater containing organic matter is aerated in an aeration basin in which microorganisms metabolize the suspended and soluble organic matter. Part of organic matter is synthesized into new cells and part is oxidized to CO2 and water to derive energy. In activated sludge systems the new cells formed in the reaction are removed from the liquid stream in the form of a flocculent sludge in settling tanks. A part of this settled biomass, described as activated sludge is returned to the aeration tank and the remaining forms waste or excess sludge.

SBR (Sequential Batch Reactor)

The Sequencing Batch Reactor (SBR) is an Activated Sludge Process designed to operate under non-steady state conditions. An SBR operates in a true batch mode with aeration and sludge settlement both occurring in the same tank. The major differences between SBR and conventional continuous-flow, activated sludge system is that the SBR tank carries out the functions of equalization aeration and sedimentation in a time sequence rather than in the conventional space sequence of continuous-flow systems. In addition, the SBR system can be designed with the ability to treat a wide range of influent volumes whereas the continuous system is based upon a fixed influent flow rate. Thus, there is a degree of flexibility associated with working in a time rather than in a space sequence.

SBR produce sludge with good settling properties providing the influent wastewater is admitted into the aeration in a controlled manner. Controls range from a simplified float and timer based system with a PLC to a PC based SCADA system with color graphics using either flow proportional aeration or dissolved oxygen controlled aeration to reduce aeration to reduce energy consumption and enhance the selective pressures for BOD, nutrient removal, and control of filaments. 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.

MBR (Membrane Bioreactors)

Membrane Bioreactor is a systems integrating biological degradation of waste products with membrane filtration. They have proven effective in removing organic and inorganic contaminants as well as biological entities from wastewater. Membrane bioreactor is the combination of a membrane process like microfiltration or ultrafiltration with a suspended growth bioreactor, and is widely used for municipal and industrial wastewater treatment.

The MBR system are available as Integrated Submerged Type & External Module Type and the advantages include good control of biological activity, high quality effluent free of bacteria and pathogens, smaller plant size, and higher organic loading rates.

MBBR (Moving Bed Bio Reactor)

Moving Bed Bio-Reactor (MBBR) processes improve reliability, simplify operation, and require less space than traditional wastewater treatment systems (ASP).

MBBR technology employs thousands of polyethylene biofilm carriers operating in mixed motion within an aerated wastewater treatment basin. 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. This technology provides cost-effective treatment with minimal maintenance since MBBR processes self-maintain an optimum level of productive biofilm. Additionally, the biofilm attached to the mobile bio carriers within the system automatically responds to load fluctuations.

The advantages that are attached with this technology are:

  1. Compact Design – A fraction of the size of ASP
  2. Expandable – Capacity could be easily upgraded by increasing the biofilm carrier
  3. No Return activated sludge stream required
  4. High Response to shock load
  5. Minimal maintenance of MLSS

Moving Bed Bio-Reactor systems deliver a flexible, cost-effective, and easy-to-operate means to address current wastewater requirements and the expandability to meet future loads or more stringent discharge requirements within a compact design.