Sewage Treatment Plant Manufacturer In Faridabad: How Is an STP's Daily Output Estimated for a Mixed-Use Building?

A builder planning a building with flats on the upper floors, a shop floor at street level, and a canteen in the basement has to answer a question early: how much sewage will this building produce each day? The answer decides the size of the plant, the cost of the civil work, and whether the approval will be accepted. Yet many estimates are a single figure multiplied by the number of flats, with the shops and the canteen added as an afterthought. A mixed-use building needs each part estimated on its own terms. Netsol Water is the best sewage treatment plant manufacturer in faridabad at best affordable price and quality.

This article shows how to build a daily sewage estimate for a mixed-use Faridabad building, using assumed occupancy and per-use figures, and how to test the result against water bills once the building is occupied.

Why One Figure Is Not Enough

Each Use Behaves Differently

A residential flat produces sewage in the morning and evening, with washing, cooking, and bathing. A shop produces modest sewage during opening hours, mostly from washrooms and occasional cleaning. A canteen produces a sharper load tied to meal times, with washing up, food preparation, and cleaning. Each use has its own daily pattern, and the plant has to cope with all of them at once.

The Peak Matters as Much as the Total

The daily total sets the average, but the peak sets the stress on the inlet, the equalisation tank, and the blowers. A canteen's lunch peak may coincide with the flat residents' morning return, and a plant sized only for the daily total can overflow at the worst moment. The estimate should give both the daily volume and the peak hour.

Building the Estimate

Residential Flats

Start with the number of flats and the occupancy per flat. Assume a figure based on the planned unit mix, not the most optimistic one. For a building of two-bedroom flats, a typical planning assumption might be four residents per flat, though the actual figure depends on the buyers.

Multiply the residents by a per-person sewage figure. Sewage is usually taken as a share of water use, since most of the water used in a home eventually reaches the drain. Assume for illustration that each resident uses 135 litres a day, and that 80% of it becomes sewage. That gives 108 litres per resident per day.

For 40 flats at four residents each, that is 160 residents, and 160 × 108 = 17,280 litres per day, or about 17.3 cubic metres.

Shops

Shops are estimated by the number of staff and customers, or by the floor area, depending on the type of shop. A general shop with a small washroom has a low figure. Assume, for illustration, that a shop on the ground floor has 4 staff and 40 customers a day, each using about 15 litres at the washroom and tap, with 80% reaching the drain. That gives (4 + 40) × 15 × 0.8 = 528 litres per day for one shop.

Multiply by the number of shops. Ten such shops produce about 5,280 litres per day, or about 5.3 cubic metres.

The Canteen

The canteen is usually the biggest single source in a small mixed-use building, and it deserves its own calculation. Estimate the number of meals served and the water used per meal in preparation and washing up. Assume a canteen serving 300 meals a day, with 20 litres of water per meal for preparation and washing, and 80% reaching the drain. That gives 300 × 20 × 0.8 = 4,800 litres per day, or about 4.8 cubic metres. Add the washroom use for the staff and customers, perhaps a further 500 litres, for a total of about 5.3 cubic metres.

The canteen's grease content also matters, and its effluent may need a grease trap upstream, which the sewage estimate does not capture.

Total Daily Volume

Adding the three parts gives 17.3 + 5.3 + 5.3 = 27.9 cubic metres per day, which is about 28 cubic metres. This is the average the plant must treat, before allowing for growth or for variation between days.

Estimating the Peak

Residential Peak

Residential sewage peaks in the morning, when people wash and cook, and again in the evening. Assume that 30% of the daily residential sewage arrives in the two hours around the morning peak. For 17.3 cubic metres per day, that is about 5.2 cubic metres in two hours, or roughly 2.6 cubic metres per hour.

Canteen Peak

Assume that the canteen's lunch service carries 40% of its daily sewage in a two-hour window. For 5.3 cubic metres a day, that is about 2.1 cubic metres in those two hours, or about 1.1 cubic metres per hour.

Combined Peak

If the morning residential peak and the lunch canteen peak overlap in part, the combined peak can reach around 3 to 4 cubic metres per hour. The inlet, the equalisation tank, and any pumps must be sized for this combined peak, not the daily average of about 1.2 cubic metres per hour. An estimate that only gives the average would leave the plant undersized for its real stress.

The peak factor used here is an assumption. The real factor depends on the building's routine, and a conservative planning assumption is often used until the building is occupied.

Adding Margin

Allowing for Growth and Occupancy

Occupancy in new buildings often differs from the plan. Some flats are let to larger households, and some shops change their trade. A margin of 10 to 20% on the design flow is a common planning allowance, though the right figure depends on the risk the developer is willing to accept.

Allowing for Variation

Daily variation is normal. A festival week, a wedding in the building, or a shop with an unusually busy season can push the flow up. The design should allow for an ordinary busy day, not only the average.

Checking the Estimate Against Water Bills

Once the Building Is Occupied

The best test of an estimate is the building's actual water use. Once the building is occupied, record the water supply meter readings over several months, then calculate the daily use per flat, per shop, and for the canteen, where meters allow. Compare these figures with the assumptions. Where the real use is higher, the plant may be undersized. Where it is lower, the plant may be oversized, and the difference is useful for future buildings.

Sub-Metering the Canteen

Install a sub-meter on the canteen's water supply if possible. It is the most variable source, and a sub-meter shows whether its use matches the estimate. Without it, the canteen figure remains a guess, and the plant's performance will depend heavily on that guess.

Reconciling the Totals

Compare the sum of the metered uses with the total supply meter. A large gap points to a leak, an unmetered use, or a source of water not going to the drain, such as garden watering. Each of these affects the sewage estimate, and the reconciliation shows which one is at play.

A Sample Summary

1) Residential flats: 40 flats, 160 residents, about 17.3 m³ per day

2) Shops: 10 shops, about 5.3 m³ per day

3) Canteen: 300 meals a day plus washrooms, about 5.3 m³ per day

4) Total daily average: about 28 m³ per day

5) Estimated peak: 3 to 4 m³ per hour

6) Planning margin: 10 to 20%, applied to the design figures

These figures are for illustration. Each building has its own occupancy, use, and habits, and the estimate should be built from the real plan and tested against real bills.

Questions to Ask Before Fixing the Plant Size

A) What occupancy and per-person figure has been assumed for the flats, and where does it come from?

B) How has each non-residential use been estimated, and what is the basis?

C) What is the peak factor, and what is the peak hour flow?

D) What margin has been added for growth, and what is it based on?

E) Will the building be sub-metered, so the estimate can be checked once it is occupied?

Summary

A mixed-use building's sewage is the sum of several different patterns, and each needs its own estimate. Build the residential, shop, and canteen figures separately, add the peak as well as the average, allow a margin, and plan a check against water bills once the building is occupied. An estimate built this way gives the plant a size that fits the building it serves, and a record that improves the next estimate.

NetSol prepares daily sewage estimates for mixed-use buildings in Faridabad, covering each use separately and setting out the peak and the margin, so the plant is sized from the building's real plan. If your project needs a sizing basis for an Sewage Treatment Plant, Netsol Water can work through the estimate with the developer's architect.