Sewage Treatment Plants

SBT System for Sewage Treatment Plants

Soil Biotechnology (SBT) has profound application in the domestic sewage recycling.  It has more than 50 installations across India.  It has been registered with Military Engineering Services, Air ports, various Jal Boards, PHE, Jal Nigam etc.  SBT has been adopted by Government of Maharashtra for its ambitious Rural Sanitation scheme.  Similar on the line it is under consideration with various other state governments for implementation of their rural sanitation programme. 
SBT systems are typically housed in RCC, stone-masonry or soil bunds and consists of an impervious containment.  It starts with a under drain layer, above which lies a layer of media housing culture and bio-indicator plants.  Water first passes through the additive layer and subsequently passes through the media.  The process can be run as single stage or multistage depending on water quality desired.  The recirculation is provided for further polishing if required.  Following figure depicts a typical sectional view of SBT system:

Process Flow & Description

The process is a batch processes in which wastewater is pumped and applied onto the top surface of the Bioreactor as shown in above figure. Raw sewage is collected in Raw Water Tank (RWT) after initial screening and settling. The raw sewage is pumped on the top of a SBT Bio Reactor where it percolates through a geological media. The treated water from BR-1 is collected and again treated to attain reuse quality and then collected at the bottom of the Bio-Reactor (BR-2) and stored in a Treated Water Tank (TWT).  The design has suitable provision for manual removal of suspended solids from the biofilter surface.  Distribution of wastewater over the media is achieved via pumping, piping and distribution arrangements.  Separate distribution lines are provided for raw wastewater as well as recycle water.  The suspended solids are filtered out which includes additives that combine with organic of waste to produce manure. Solids are typically retained in the settling tank and then can be removed mechanically. Water first percolates through the bioreactor media which in houses cultured media in 40-60 min and gets collected into the collection tank. It can then be pumped on to the media again (recycling) in order to achieve maximum solid liquid contact. The recirculation mode is provided for further polishing of the effluent. Dissolved organic and inorganic are oxidized and the water is purified further.

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