The right STP design and capacity calculation for schools and colleges depends on several factors. Educational institutions generate about 45 liters of water discharge per student daily, according to the Indian Pollution Control Board. The most important finding shows that 80% of this water (36 liters per student) needs proper treatment as wastewater.
Educational facilities’ sewage treatment units need specific parameters in their planning. School wastewater typically contains BOD levels of 250-350 mg/L and COD levels of 500-600 mg/L. Student population plays a crucial role in the STP formula capacity calculation. A school with 1000 students generates approximately 36,000 liters of wastewater daily. The design must include a safety factor of 1.5, which brings the required STP capacity to around 52.5 KL/day in this case.
Let’s explore everything in calculating STP capacity for educational institutions accurately. This piece will guide you through the parameters that shape design decisions. You’ll find practical formulas that help your facility meet regulatory requirements and operate at peak efficiency.
Estimating Wastewater from Daily Activities in Schools
Building effective sewage treatment plants starts with a clear picture of how educational institutions use water daily. The right wastewater volume estimates help calculate the perfect STP capacity.
Bathing, Dishwashing, Flushing: Flow Rate Assumptions
Schools and colleges create wastewater from many sources. Toilet flushing uses the most water. Each flush needs 9-12 liters, which is a big deal as it means that it needs more than the 5 liters we use for cooking and drinking. Residential schools generate much more wastewater from their bathing facilities than day schools do.
The 80:20 rule applies to wastewater – about 80% of water used turns into wastewater. So a school using 45,000 L/d of water will create around 36,000 L/d of wastewater. Engineers also need to factor in peak flow rates at 1.2 times normal flow, which comes to 43,200 L/d in this case.
Activity-wise Wastewater Contribution in LPD
Educational institutions produce two types of wastewater:
- Blackwater: Contains fecal matter from toilets
- Greywater: Comes from sinks, showers, and washing machines
University campus studies show greywater makes up most of the wastewater volume. One case study found that from 1,529,288 liters of daily wastewater, greywater made up about 1,285,277 L/day (84%), while blackwater was only 244,010.6 L/day (16%).
Garden watering can affect water use by a lot. Using local plant varieties and xerophytes helps cut down water needs. Watering plants at the right time avoids high evaporation and saves water.
STP Tank Full Form and Role in Collection
STP (Sewage Treatment Plant) collects and treats wastewater before releasing it into the environment. It handles both organic and inorganic pollutants, which we measure as BOD and COD.
Schools and colleges typically show BOD levels of 250-350 mg/L and COD levels between 500-600 mg/L. The Central Pollution Control Board (CPCB) requires educational institutions to treat their wastewater in properly sized STPs. This treated water can then be reused for gardens, flushing, or cooling towers.
Population Equivalent (PE) and Flow Rate Estimation
Population Equivalent (PE) calculations are the foundations of determining accurate STP capacity in educational institutions. This standardized measurement helps engineers size treatment facilities properly by converting different wastewater loads into equivalent population units.
PE Calculation for Day Schools vs Residential Schools
Day schools and residential schools create substantially different wastewater volumes because they operate differently. Day schools need 0.2 PE per student to calculate PE. This lower factor reflects students’ limited water usage during school hours. Residential schools need 1 PE per student because students live on campus and use water for all daily activities.
Schools with both day and boarding students need separate calculations for each group. The formula adds up like this: (0.2 × number of day students) + (1 × number of residential students). A school’s PE with 300 day students and 200 residential students would calculate to (0.2 × 300) + (1 × 200) = 260.
Flow Rate = PE × 225 LPD (MS1228 Standard)
Malaysian Standard MS1228 provides a simple formula after determining PE: Average Daily Flow = 225 liters per day × PE. Each person uses about 225 liters of wastewater daily according to this standard. Actual measurements sometimes show higher values up to 0.36 m³/day/person.
Design flow calculations become simple with this formula. Our example school with 260 PE would have an average daily flow of: 260 × 225 = 58,500 liters per day.
Peak Flow Factor Based on PE Size
STP design must handle peak periods when wastewater spikes. The peak flow factor uses this formula: PFF = 4.7 × p^-0.11. Here, p represents population equivalent in thousands.
Let’s calculate for our example school (PE = 260 or 0.26 thousand): PFF = 4.7 × (0.26)^-0.11 = 4.7 × 1.15 = 5.4
Peak flow reaches 5.4 times the average flow rate, totaling 315,900 liters per day. This peak capacity will give the STP enough room to work during high-usage periods without failing.
STP Design Parameters and System Selection
Calculating the PE is the first step in selecting a suitable sewage treatment system. The system’s technical specifications must meet both regulatory standards and institutional needs.
Choosing Between Septic Tank and STP Based on PE
PE values determine the choice between a septic tank and STP. Educational institutions with PE below 75 can use a septic tank system effectively. Septic tanks work well for smaller facilities because they cost less to install, need simple maintenance, and use minimal energy.
Schools and colleges with PE above 75 need a full-fledged STP. STPs clean wastewater more effectively by removing more pollutants through multiple stages compared to the simple solid-liquid separation in septic tanks. The higher upfront cost of STPs is worth it since they can handle large volumes – perfect for residential schools or bigger institutions.
Rotating Biological Contactor (RBC) vs ASP
Educational institutions often choose between two biological treatment technologies: Rotating Biological Contactors (RBC) and Activated Sludge Process (ASP). RBCs use rotating disks that sit partially in wastewater. Microorganisms grow on the surface and break down organic matter. These systems work best at 1-10 RPM with water staying in the system for 4-24 hours.
ASP systems take a different approach. They use aeration tanks where microorganisms float in the wastewater. Here’s how the two systems compare:
- Energy Requirements: RBCs use less power, which saves money over time
- Space Efficiency: RBCs need less space than ASP systems – great for space-constrained institutions
- Maintenance: RBCs have simpler designs that need less upkeep
- Odor Control: RBCs manage odors better than ASPs, which matters a lot for residential campuses
- Performance: Both clean water similarly well – RBCs remove 83.17% COD while ASPs achieve 88.28%
Design of Sewage Treatment Plant PDF Reference Standards
Detailed reference documents guide the design of educational institution STPs. These standards detail the treatment stages: preliminary, primary, secondary, and tertiary processes.
The size of treatment units, how well they work, and environmental compliance are key design parameters. STP capacity design must consider hydraulic loading rates, organic loading rates, and expected population growth.
Most designs plan for 20-30 years ahead and account for future increases in student numbers. Designers calculate average sewage generation (usually 85% of water supply) and peak flow factors (typically 3 times average flow).
Infrastructure Considerations for STP Installation
The way an STP’s physical infrastructure is built affects its performance by a lot in educational institutions. Building it right needs careful attention to pipe networks, where manholes go, and how gravity makes things flow.
Pipe Sizing and Gradient Requirements
The size of pipes directly shapes how well an STP works, and minimum diameter requirements are vital here. The Central Public Health and Environmental Engineering Organization (CPHEEO) manual suggests 150 mm as the standard minimum pipe diameter at first. All but one of these regions can use this – hilly areas can work with 100 mm pipes. In spite of that, several states and urban local bodies now prefer bigger minimum diameters of 200 mm or 250 mm to lower blockage risks.
There are three main reasons behind this change:
- People don’t maintain sewer systems well enough, so smaller pipes get blocked often
- Small RCC mains aren’t built well enough most times
- Sewer systems usually have gaps that let solid waste get in
The right gradient will give a self-cleansing speed without too much wear. Gravity sewers need proper slopes to keep minimum flow speeds at 0.6 m/s during peak dry weather flow.
Manhole Placement and Drop Manhole Criteria
Manholes are the foundations of inspection and maintenance access. They need to be built wherever alignment, gradient, or pipe size changes, and at every sewer junction. The space between manholes changes based on sewer diameter:
| Sewer Diameter | Maximum Manhole Spacing |
|---|---|
|
Up to 0.3 m |
45 m |
|
Up to 0.6 m |
75 m |
|
Up to 0.9 m |
90 m |
You’ll need drop manholes when water lines differ by more than 600 mm. These special structures use vertical or near-vertical drop pipes that end with a plain or duck-foot band. They release flow at 45 degrees or less toward the main sewer’s direction.
STP Capacity Calculation for Gravity Flow Systems
Educational institutions’ gravity flow systems need a specific formula to calculate STP capacity: Capacity = Peak Flow Generation × Detention Time. Detention usually takes 6-12 hours, though 8 hours is typical.
Let’s look at an example. A school generates 70,400 liters of wastewater daily with a peak flow factor of 2.2:
- Peak Flow = 70,400 × 2.2 = 154,800 liters per day
- Capacity = 154,800 × 0.5 = 77,400 liters (77.4 m³)
The settling tank’s depth usually sits at 3 meters, which means you need about 25.8 m² of area. Good infrastructure planning will give a smooth STP operation throughout its life.
Why Choose SUSBIO and SUSBIO ECOTREAT for School and College STPs
When it comes to implementing a reliable, long-lasting, and regulatory-compliant STP in educational institutions, SUSBIO and its flagship technology SUSBIO ECOTREAT stand out as industry leaders in India and emerging global markets. These systems are specifically engineered to address the dynamic and sensitive wastewater treatment needs of schools, colleges, and university campuses.
Engineered for Variable Loads
Student attendance varies during holidays, summer breaks, and exams. SUSBIO ECOTREAT’s modular and adaptive design automatically adjusts to low and high flow conditions without compromising performance. This makes it ideal for institutions with fluctuating wastewater volumes.
Plug-and-Play Installation
Educational facilities often face construction or space constraints. SUSBIO ECOTREAT’s prefabricated, containerized units offer quick deployment and easy relocation—reducing project timelines and eliminating the need for heavy civil work.
Energy Efficient & Low Maintenance
School and college campuses benefit from the low-energy operation of SUSBIO systems. The units run on smart control logic that minimizes blower and pump usage, thereby reducing electricity bills. With self-cleaning filters and minimal moving parts, they also require low operational maintenance, ideal for campuses with limited technical staff.
Treated Water Safe for Reuse
SUSBIO systems produce high-quality treated effluent with BOD < 10 mg/L and TSS < 10 mg/L—perfect for irrigating lawns, flushing toilets, and cooling systems. This enables water conservation and contributes toward a green campus initiative.
CPCB and Local Authority Approved
All SUSBIO solutions meet the discharge norms set by CPCB, state PCB authorities, and ULBs. The systems can be easily integrated into the institution’s environmental compliance frameworks including NABL, NAAC, and green building certifications.
Smart Monitoring with Optional IoT Integration
SUSBIO ECOTREAT units offer remote monitoring via IoT, which allows school administrators or facility managers to track flow rates, pH levels, and system status in real time. This reduces manual oversight and ensures maximum uptime.
Proven Track Record in Educational Campuses
From K–12 schools to large universities, SUSBIO has delivered over 200+ STP installations across India and overseas, making it a trusted partner for both public and private educational institutions. Its solutions are currently running in hostels, cafeterias, auditoriums, and campus townships—serving over 300,000 students daily.
Conclusion
Educational institutions need the right STP capacity calculations to manage wastewater well. This piece walks you through the complete process to determine sewage treatment needs based on student numbers, how they use water, and the type of institution.
Getting the numbers right starts with a basic rule – 80% of water used becomes wastewater that needs treatment. The difference between day schools (0.2 PE per student) and residential facilities (1 PE per student) substantially affects how much capacity you need.
Standard flow rate calculations use the 225 LPD formula as their base. Peak flow factors help systems handle maximum loads when usage spikes. This prevents systems from overflowing and keeps operations running smoothly.
Your system choice depends on PE values. Septic tanks work fine for smaller populations under 75 PE. Bigger institutions need full STPs. RBC and ASP systems each have their trade-offs in energy use, space needs, maintenance, and how well they treat waste.
The right pipe sizes, gradient requirements, and smart manhole placement make the whole system work at its best throughout its life. These technical details might seem daunting at first. But when you implement them carefully, you get a system that works well and meets all rules.
Schools and colleges that use these calculation methods will meet all regulatory requirements. They’ll create environmentally responsible campuses too. Best of all, they’ll build water management systems that help both their institutions and nearby communities for years to come.
Key Takeaways
Understanding proper STP capacity calculation is essential for educational institutions to meet regulatory requirements and ensure efficient wastewater management.
- Use the 80:20 rule: 80% of water consumption becomes wastewater requiring treatment, with schools generating approximately 36 liters per student daily.
- Apply correct PE factors: Day schools use 0.2 PE per student while residential schools require 1 PE per student for accurate capacity calculations.
- Calculate flow using MS1228 standard: Average daily flow = PE × 225 LPD, then apply peak flow factors (typically 1.2-5.4x) for proper sizing.
- Choose systems based on PE: Septic tanks work for PE below 75, while full STPs are necessary for larger institutions above 75 PE.
- Plan infrastructure carefully: Use minimum 150-200mm pipe diameters, maintain proper gradients for self-cleansing velocity, and place manholes strategically for maintenance access.
When implemented correctly, these calculations ensure your educational facility operates a compliant, efficient sewage treatment system that serves the institution reliably for 20-30 years while protecting environmental standards.
FAQs
How is STP capacity calculated for educational institutions?
STP capacity is calculated based on the student population and type of institution. For day schools, use 0.2 PE (population equivalent) per student, while for residential schools, use 1 PE per student. Multiply the total PE by 225 liters per day to get the average daily flow rate.
What factors influence STP design for schools and colleges?
Key factors include the number of students, whether it’s a day or residential school, peak flow rates, and infrastructure considerations like pipe sizing and gradient requirements. The design should also account for potential population growth over a 20-30 year horizon.
How much land is typically required for an STP in educational facilities?
Land requirements vary based on the institution’s size and treatment system chosen. However, for large developments or township projects spanning 10 acres or more, an efficient STP system is mandatory to handle sewage load and wastewater recycling while complying with local regulations.
What are the main stages in a sewage treatment plant for schools?
A typical STP for educational institutions includes preliminary treatment (to remove floating particles), primary treatment (sedimentation), secondary or biological treatment (to convert unstable organic matter), and tertiary treatment (such as chlorination or UV radiation).
How do you choose between a septic tank and a full STP for a school?
The choice depends on the institution’s size. For schools with a population equivalent (PE) below 75, a septic tank system is generally sufficient. However, for larger institutions with PE exceeding 75, a full-fledged STP becomes necessary to handle the higher wastewater volume and meet regulatory standards.
