STP Cost Calculator
Estimate the cost of a sewage treatment plant for your apartment complex, commercial building, hospital, or school. Get indicative CAPEX, monthly OPEX, and a technology recommendation — in under 60 seconds.
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For apartments, commercial buildings, hospitals, and schools.
Typical rates: Residential 135 lpcd | Hospital 340 lpcd | Office/School 45 lpcd
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STP Cost in India: What Drives the Price?
Sewage treatment plant costs in India are primarily driven by flow rate (KLD), output quality required, and application type. Residential apartment STPs are the most common — under Indian standards, every new residential project above 500 sq m or 50 units must install an STP. The standard design norm is 135 litres per person per day (CPHEEO), so a 300-flat complex with 4 persons/flat generates approximately 162 KLD of sewage.
A good rule of thumb for residential STPs in India is ₹1,500–2,500 per person for a turnkey installed system, including civil work, equipment, electrical, and commissioning. This means a 300-flat project (1,200 persons) can expect to pay ₹18–30 lakhs for the STP component — roughly ₹6,000–10,000 per flat. Builders typically recover this in common area maintenance charges.
Flush Reuse vs Irrigation vs Discharge: Why Output Quality Matters
The single biggest decision after flow rate is what you want to do with the treated water. An STP designed for toilet flush reuse must meet much stricter quality standards (BOD <10 mg/L, TSS <10 mg/L, coliform-free) compared to one designed for garden irrigation (BOD <100 mg/L). This requires additional treatment stages — a tertiary filter and UV/chlorine disinfection — adding 15–25% to CAPEX but dramatically improving the value of the recovered water.
For large apartment complexes where 25–35% of water consumption is for toilet flushing, the flush reuse upgrade can save ₹5–15 lakhs per year in water bills, paying back the additional capex in 2–4 years. Many green-rated buildings (IGBC Gold/Platinum, LEED) make flush reuse a mandatory requirement.
STP Cost Benchmarks for Different Applications
| Application | Flow | CAPEX Range | Monthly OPEX |
|---|---|---|---|
| Small Society (100 flats) | ~18 KLD | ₹27–55 L | ₹10–19K |
| Mid Society (300 flats) | ~54 KLD | ₹70–138 L | ₹29–57K |
| Large Township (1000 flats) | ~180 KLD | ₹2.0–3.6 Cr | ₹97K–1.9L |
| 200-bed Hospital | ~68 KLD | ₹89–178 L | ₹37–73K |
| IT Park / Office (1,000 staff) | ~45 KLD | ₹59–118 L | ₹24–47K |
| School (2,000 students) | ~90 KLD | ₹1.1–2.1 Cr | ₹49–95K |
Indicative ranges for CPHEEO-compliant STP with basic discharge quality. Flush reuse adds 20–25%. Figures include civil, mechanical, electrical, and commissioning.
What Is Included in STP Turnkey Cost?
A turnkey STP contract from Spans includes civil construction (underground/above-ground RCC tanks), mechanical equipment (screens, pumps, blowers, diffusers, filter presses), process equipment (MBBR media, SBR control systems, UF membranes if specified), electrical systems (MCC panel, cabling, instrumentation, SCADA), piping and valves, and commissioning with operator training. Land and external plumbing connection are typically outside scope.
Spans also offers O&M contracts post-commissioning — ensuring the STP meets discharge standards year-round without the builder or RWA having to manage day-to-day operations. Monthly O&M contracts typically cost ₹20,000–75,000 depending on plant size and output quality requirements.
Frequently Asked Questions
How much does an STP cost for a residential apartment in India?
STP cost for residential apartments ranges from ₹1,500–2,500 per person turnkey. For a 500-person complex (67 KLD), expect ₹75 L–1.25 Cr all-inclusive. Smaller 10 KLD packaged units cost ₹20–40 lakhs.
Is an STP mandatory for apartments in India?
Yes. Under RERA and local building bylaws, STPs are mandatory for residential projects above threshold sizes in most states including Maharashtra, Karnataka, Tamil Nadu, Delhi, Gujarat, and Telangana. Non-compliance can block occupancy certificates.
Which technology is best for apartment STP?
MBBR (Moving Bed Biofilm Reactor) and SBR (Sequencing Batch Reactor) are most popular. For flush reuse quality, MBR gives the best output. Packaged MBBR systems are compact and suitable for space-constrained sites. Spans recommends technology after reviewing sewage flow pattern and output requirements.
What is the monthly STP maintenance cost?
Monthly STP OPEX ranges from ₹10,000 for a 10 KLD plant to ₹1–2 lakhs for a 200 KLD plant. This covers electricity (aeration blowers), chemicals, operator salary, and routine maintenance. Annual OPEX is typically 3–5% of plant CAPEX.
How long does it take to install an STP for an apartment?
A packaged STP (10–30 KLD) takes 60–90 days from order. A custom civil STP (50–200 KLD) takes 4–7 months for design, civil construction, and commissioning. Spans offers fast-track delivery for projects with occupancy certificate deadlines.
Get Your STP Designed & Installed
Spans Envirotech delivers turnkey STP projects for residential, commercial, and institutional clients across India. From design to commissioning to O&M — one partner for the entire lifecycle.