Sewage Treatment Plants And Sewerage System

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Sewage Treatment Plants & Sewerage System

The objective of the sewage scheme is to aid the collection of the sewage or domestic wastewater from each household through pipelines, and intermediate pumping stations, to take it to a common facility which is called a Sewage Treatment Plant where this sewage water is treated upto the current stringent norms prescribed by NGT or upto the standards to reuse this treated water in horticulture, refrigeration and processing industries etc.

The sewerage waste water is rich in Nitrogen and Phosphorous besides organic matter which acts as Carbon source, which aids in formation of organic cells. A no. of technologies are available for Biological Treatment of Sewage waste water in combination of technologies for Biological Nutrient Removal.

Sewage treatment plants employ a combination of all or any one of the following systems for treatment of water to usable standards:

  • Primary Treatment Units- For removal of large particles/ solids from sewage.
  • Aeration – for the removal of BOD and COD in sewage. There are two types of biological systems:
    aerobic which acts in presence of air and anaerobic systems which operates in absence of oxygen. There are various technologies available for removal of BOD and COD.

    The aerobic systems include:
    • Activated Sludge Process
    • Extended Aeration System
    • Diffused Aeration System
    • MBBR (Mixed Bed Biological Reactor)
    • SAFF (Submerged Aerated Fixed Film Reacotr)
    • IFAS
    • SBR (Sequential Batch Reactor)
    • MBR (Membrane Bio Reactor)
    The anaerobic systems include:
    • UASB (Upflow Anaerobic Sludge Blanket Reactor)
    • High Rate Anaerobic Digestor

We have the design capabilities to design systems on any of these technologies and have already installed plants based on these technologies. However, presently the majority of our sewage treatment plants are based on Sequential Batch Reactors which has its inherent advantages of integrated BNR removal system, which aids in meeting the stringent norms, small footprint area and complete automation of systems. A recent technological advancement by our Company is to provide High Rate Anaerobic Digestor (HRAD) followed by SBR, along with BNR removal even at low BOD concentrations. Further, we are offering MBBR in various combinations like IFAS in already existing/ partly build systems, to use existing the infrastructure to its maximum by avoiding major civil works, and provide cost effective and viable solutions, meeting the effluent norms at the same time. Over the years we have deployed several tertiary treatment technologies such as dual media filters, activated carbon filters, rapid sand gravity filters, chlorination, UV treatment. We are also providing disc filters, ultra-filtration in our ongoing projects.

  • Sedimentation – removal of suspended particles present in water. For sedimentation we employ conventional clariflocculator technology, advanced space saving technologies like inclined plate settler technology and tube settler technology.
  • Filtration –wherein the water will be filtered through a media of sand for removal of fine suspended particles present in water. For filtration we employ superior nozzle based under drain system for collecting filtered water which ensures superior quality compared with conventional header and lateral systems. Depending upon the requirement of quality, we also offer space saving dual media gravity filtration where anthracite or carbon is used in addition to sand as filtration media.
  • Disinfection – for controlling microbial substances likes bacteria and viruses present in water. Depending upon the requirements, we use chlorine, ozone or ultra violet rays as disinfectants
  • Sludge Dewatering – The sludge generated from the facilities is dewatered using equipment such as centrifuge vacuum filter, filter press or dried on sludge drying beds.

Sewerage Schemes

The sewerage schemes in India are of two types. The first where the sewerage flowing into river(s) or any water body is diverted to an STP in certain cities where sewer lines have not been laid. The second one is in which the sewer line are already laid connecting to the STP before disposal into water body or its reuse. Since the flow through sewer lines is by gravity, utmost care is required to be taken to design the system to be hydraulically correct and at the same time the sewer system is designed in order to have self-cleaning velocities to prevent any choking in sewer lines. For sewerage scheme projects we begin with the survey of the entire area where sewer is to be laid, design of the sewerage system, design of STP, providing and laying of sewerage pipes, civil construction, supply, erection, testing and commissioning of STP, followed by operation and maintenance for the designated period as per the work order.