SJVN Thermal Township (via Hitech Competent Builders Pvt. Ltd.)
The Challenge
Reuse-Grade Sewage Treatment for a Thermal-Power Township
The SJVN Thermal Private Limited power-plant township at Buxar needed a sewage treatment plant for its residential and commercial areas. Spans Envirotech was engaged — through the township's builder, Hitech Competent Builders — to design and deliver the plant, treating typical domestic sewage of around BOD 400 mg/L, COD 600 mg/L and TSS 200 mg/L.
The township wanted treated water clean enough to reuse for horticulture, lawn irrigation and flushing. Meeting a reuse target of TSS below 5 mg/L is well beyond what a basic secondary STP delivers, so the design had to add tertiary polishing without over-building the whole plant.
Key Issues:
- !Domestic township sewage — BOD 400 mg/L, COD 600 mg/L, TSS 200 mg/L
- !Reuse targets for horticulture and flushing, requiring TSS <5 mg/L with tertiary polishing
- !Scope scaled from 300 KLD to 335 KLD during design, plus a 120 KLD polishing stream
- !CPHEEO-compliant design for a PSU power-plant township
The Solution
A CPHEEO-Compliant MBBR Core with Right-Sized Ultrafiltration Polishing
Spans designed the plant around a Moving Bed Biofilm Reactor (MBBR) core per CPHEEO guidelines. The process train sequences an inlet sump, a selector/anoxic tank, MBBR aeration, a tube settler and a clarified-water tank, followed by pressure sand and activated carbon filtration before the treated-water tank. Sludge is routed to dewatering beds for reuse as manure.
To meet the elevated reuse standard, Spans added a 120 KLD ultrafiltration stream as a polishing step rather than upsizing the entire plant — right-sizing tertiary treatment to the fraction of flow that needs reuse-grade quality (TSS <5 mg/L). As the brief evolved, the plant was scaled from 300 to 335 KLD. Spans' scope covered design and detailed engineering (PFD, HFD, P&ID, GA drawings), procurement, fabrication, supply, erection and integration of the electro-mechanical equipment, testing, commissioning and stabilization, with PMC supervision; civil works were executed by the client's contractor to Spans' drawings.
Technologies Deployed:
Implementation Timeline:
Design Basis & Capacity Sizing
Set the CPHEEO-compliant design basis for township sewage and sized the MBBR plant — scaled from 300 to 335 KLD as the brief developed.
MBBR Process Engineering
Engineered the inlet, anoxic and MBBR aeration stages, tube settler and PSF/ACF filtration to secondary reuse quality.
Ultrafiltration Polishing
Added a right-sized 120 KLD UF stream to reach TSS <5 mg/L for horticulture and flushing reuse without upsizing the whole plant.
Supply, Erection & Commissioning Scope
Procurement, fabrication, supply, erection and integration of E&M equipment with testing, commissioning, stabilization and PMC supervision.
The Results
Engineering & Design Highlights
335 KLD
Design Capacity
MBBR sewage treatment plant sized for the township, scaled up from 300 KLD
120 KLD UF
Tertiary Polishing
Right-sized ultrafiltration stream for reuse-grade water
TSS <5 mg/L
Reuse Target
Treated water designed for horticulture, lawn irrigation and flushing
MBBR (CPHEEO)
Technology
Moving Bed Biofilm Reactor core per CPHEEO guidelines for a PSU township
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