INDUSTRIES / SUGAR
Sugar mill effluent treatment
that turns cane water into reuse water.
Cane is about 70 per cent water, so a well-run sugar mill can run almost entirely on the water it gets from the cane. We test your effluent and condensate in our NABL-accredited laboratory, then design the ETP and condensate polishing unit that cut fresh water intake and keep the outlet within your consent through the whole crushing season.
In short
How sugar mill wastewater is treated.
A sugar mill effluent treatment plant (ETP) treats the wastewater from mill house washing, the boiling house, spray pond overflow, boiler blowdown and excess condensate. The water carries sucrose and other sugars, so it has a high BOD and COD, turns acidic and smelly within hours, and arrives only during the crushing season. It is treated by screening and oil removal, equalisation with pH correction, an anaerobic reactor that turns the sugar load into biogas, aerobic polishing and filtration. Excess condensate, the cleanest stream, is treated separately in a condensate polishing unit (CPU) and reused. Under the Environment (Protection) Rules, 1986, sugar mills must meet CPCB's sugar industry standard and the conditions in their consent.
- ~70%
- Water content of sugarcane, released as vapour condensate in the boiling house
- 3–4%
- Press mud (filter cake) produced, as a share of cane crushed
- 30mg/L
- BOD limit for treated sugar effluent discharged to inland surface water
- 17categories
- Highly polluting industries required to run online monitoring; sugar is one
Where it comes from
Where does sugar industry wastewater come from?
A cane sugar mill runs for a crushing season of roughly four to six months, usually from about October or November to April, depending on the state and the cane supply. During the season it runs around the clock; in the off-season it is shut for maintenance. Wastewater comes from both the cleaning of equipment and the water cycles of the boiling house.
| Source | What happens there | What it adds to the effluent |
|---|---|---|
| Mill house washing | The cane carrier, mills, juice troughs and floors are washed to stop juice fermenting on surfaces | Spilt juice (high BOD), bagasse fibre, soil, lubricating oil and grease from mill bearings |
| Boiling house washing | Clarifiers, evaporators, vacuum pans, crystallisers and centrifugals are cleaned; leaks and spills from pumps and tanks | Juice, syrup and molasses traces; the strongest organic load in the plant |
| Evaporator and pan cleaning | Scale is boiled out of evaporator tubes with caustic soda and acid, usually in the off-season or at scheduled stops | Short slugs of very high or very low pH, scale solids and high COD |
| Excess condensate | Water evaporated from juice in the evaporators and pans is condensed; part goes back to the boiler and process, the rest is surplus | Large volume of warm, low-solids water with some sugar carried over and volatile organics |
| Spray pond and cooling tower overflow | Injection water for the barometric condensers is cooled in a spray pond or cooling tower and recirculated | Sugar entrained from the pans and evaporators, which raises BOD and grows slime; heat |
| Boiler blowdown | Bagasse-fired boilers blow down to control dissolved solids | Hot water with high TDS, alkalinity and boiler treatment chemicals |
Typical effluent characteristics
| Parameter | Typical range | Why it matters |
|---|---|---|
| pH | 4.5 to 7, falling as sugars ferment | Effluent left standing turns acidic within hours; biology needs pH correction |
| BOD | 1,000 to 2,500 mg/L | Sugars are very biodegradable, so oxygen demand is high and odour starts fast |
| COD | 2,000 to 5,000 mg/L | A BOD : COD ratio of about 0.5 suits anaerobic plus aerobic treatment |
| Suspended solids | 200 to 800 mg/L | Bagasse fibre (bagacillo), soil and lime mud settle in drains and tanks |
| Oil and grease | Present from mill bearings and gearboxes | Coats the biomass and floats in clarifiers; removed at the front end |
| Nitrogen and phosphorus | Low relative to the BOD | Sugar effluent is nutrient-poor; urea and phosphate are usually dosed for the biology |
| Temperature | Warm; condensate and blowdown can be 50 °C or more | Hot streams must be cooled before the biological stages |
| Excess condensate COD | Low, but rises sharply with entrainment | Decides whether condensate can be reused directly or needs polishing |
The single biggest lever in a sugar mill is housekeeping before treatment. Juice and molasses that reach the drain multiply the ETP load, and good entrainment separators on evaporators and pans keep sugar out of the condensate and spray pond. Every kilogram of sugar saved is also sugar sold.
Standards and rules
Which standards apply to sugar mill effluent?
The Environment (Protection) Rules, 1986 contain an industry-specific standard for the sugar industry, which MoEF&CC revised in 2016 to add limits on how much wastewater a mill may generate per tonne of cane crushed. The main concentration limits are below. Your consent to operate may be stricter, and many boards now push sugar mills towards full reuse.
| Parameter | Inland surface water | On land for irrigation |
|---|---|---|
| pH | 5.5 to 8.5 | 5.5 to 8.5 |
| BOD (3 days at 27 °C) | 30 | 100 |
| Total suspended solids | 100 | 200 |
| Oil and grease | 10 | 10 |
| Wastewater generated | Capped per tonne of cane crushed in the revised standard; check the figure in your consent | |
Treatment scheme
A sugar mill ETP, stage by stage.
This is the scheme we start from for a cane sugar mill. The process effluent and the excess condensate are kept in separate lines: mixing a large volume of nearly clean condensate into the ETP only makes the ETP bigger and wastes reusable water.
- 1
Screen and remove oil
Bar and fine screens catch bagacillo and cane trash. An oil and grease trap at the mill house drain removes lubricant before it reaches the main line.
- 2
Settle grit and equalise
A grit chamber removes soil and lime mud. An equalisation tank with mixing, sized for at least a day of flow, evens out washing peaks and the pH swings from evaporator cleaning.
- 3
Correct pH and add nutrients
Lime or caustic brings the pH to about 6.8 to 7.5. Urea and phosphate are dosed because sugar effluent is short of nitrogen and phosphorus.
- 4
Anaerobic treatment
An upflow anaerobic sludge blanket (UASB) reactor or an anaerobic contact digester converts most of the BOD into biogas, which can be burnt in the boiler or a flare.
- 5
Aerobic polishing
Extended aeration, an activated sludge process or a moving bed biofilm reactor (MBBR) removes the remaining BOD, followed by a secondary clarifier.
- 6
Tertiary filtration and reuse
A pressure sand filter and activated carbon filter polish the water for cane yard washing, ash quenching, gardening or irrigation within the land limits.
Treatment options compared
| Option | Best for | Watch-outs |
|---|---|---|
| UASB plus extended aeration | Most mills of 2,500 TCD (tonnes cane per day) and above with steady housekeeping | Granular sludge must be protected in the off-season and restarted carefully |
| Anaerobic lagoon plus aerobic lagoon | Older mills with plenty of land | Odour, methane escape and seepage to groundwater; boards now discourage open anaerobic lagoons |
| Extended aeration alone | Small mills, khandsari and gur units, or effluent already low in BOD after good housekeeping | High power for aeration and large sludge volume at high loads |
| MBBR | Upgrading an existing aeration tank without new civil work | Media retention screens must be kept clean of bagacillo |
Our NABL-accredited laboratory tests pH, BOD, COD, suspended solids, oil and grease, TDS and nutrients in your effluent, and COD, TDS and hardness in your condensate, so the ETP and CPU are designed on real numbers.
Reuse and recovery
Condensate polishing, press mud and biogas.
A sugar mill is unusual among industries: it takes in water locked inside the cane. When juice is concentrated into syrup and then sugar, most of that water leaves the evaporators and pans as vapour and is condensed. Part of it returns to the boiler and process; the surplus is called excess condensate. Reusing it is how a mill moves towards little or no fresh water intake.
What a condensate polishing unit does
A condensate polishing unit (CPU) is a small treatment plant for excess condensate. The condensate is low in dissolved salts but carries some sugar from entrainment and volatile organics, so it slowly grows slime and smells if stored. A typical CPU cools the condensate in a cooling tower, removes the organics biologically in an aerated tank or MBBR, then filters it through sand and activated carbon. The polished water suits cooling tower and spray pond make-up, washing and lime slaking; for boiler feed, ion exchange or RO may be added after checking the boiler maker's limits.
Press mud: compost and biogas
Press mud, also called filter cake, is the mud filtered out during juice clarification. It is rich in organic matter, wax, fibre, nitrogen and phosphorus. It is traditionally composted, alone or with distillery spent wash, and sold to cane farmers as organic manure. It is also one of the most used feedstocks for compressed biogas (CBG) plants under the government's SATAT scheme, which gives a ready buyer for the gas. Our biogas and Bio-CNG team designs press mud CBG plants with the digestate processed into fermented organic manure. For integrated sugar-distillery complexes, see our distillery and ethanol guide.
Cost
How much does a sugar mill ETP cost?
The cost depends on crushing capacity, how much wastewater the mill actually generates per tonne of cane, and whether condensate is polished separately. Housekeeping changes the answer: a mill that keeps juice out of its drains needs a smaller plant.
| Plant | Typical scope | Indicative cost* |
|---|---|---|
| 200 to 500 KLD ETP, aerobic | Small mill or gur and khandsari unit: screens, equalisation, extended aeration, clarifier, filters | ₹40 lakh to ₹1.2 crore |
| 500 to 1,000 KLD ETP, anaerobic plus aerobic | 2,500 to 5,000 TCD mill: UASB, aeration, clarifier, sludge handling, filters | ₹1.2 to 3.5 crore |
| Condensate polishing unit, 500 to 1,500 KLD | Cooling, aerobic treatment, sand and carbon filtration, storage | ₹60 lakh to ₹2.5 crore |
| Upgrade of an existing ETP | MBBR media, diffusers, nutrient dosing, automation | ₹20 lakh to ₹1 crore |
*Indicative 2026 ranges for equipment, electricals and installation, excluding land, civil works and taxes. Biogas use, the level of reuse and the state of existing tanks change the figure a lot, so we price only after testing. Running costs for a sugar ETP are typically ₹10 to 30 per m³, mostly power for aeration, nutrients and sludge handling, and only during the season.
What drives capital cost
- Crushing capacity and season length
- Wastewater per tonne of cane
- Anaerobic stage or aerobic only
- Separate condensate polishing
- Storage for off-season and reuse
What drives running cost
- Power for aeration and pumping
- Urea, phosphate and pH chemicals
- Sludge dewatering and disposal
- Re-seeding the plant each season
- Monitoring and testing
Where mills lose money
- Juice and molasses lost to drains
- Condensate sent to the ETP instead of reuse
- Groundwater drawn while condensate overflows
- Slow ETP start-up delaying compliance
- Press mud sold cheaply instead of used
We measure your condensate quality and volume over a few days of crushing, then size a CPU that puts that water back into your cooling, washing and process circuits.
Troubleshooting
Common sugar mill ETP problems, and how we fix them.
- 01The problem
The ETP takes weeks to perform after the off-season, and the outlet fails in the first month of crushing.
What we doKeep the anaerobic sludge alive in the off-season with occasional feeding, re-seed the aeration tanks with active sludge before crushing begins, and ramp the load up over the first weeks with nutrient dosing and daily testing.
- 02The problem
The drains and equalisation tank smell sour and the pH drops below 5.
What we doFind and stop juice and molasses losses at source, keep drains flowing so sugars do not ferment in still water, and automate lime dosing at equalisation.
- 03The problem
Sludge in the aeration tank does not settle and solids wash out of the clarifier.
What we doSugary, nutrient-poor effluent encourages filamentous bulking. We correct the nitrogen and phosphorus dose, fix dissolved oxygen and adjust the food to biomass ratio.
- 04The problem
The spray pond water is slimy and the condensers lose vacuum.
What we doCheck entrainment separators on pans and evaporators, and supply biocide and dispersant programmes for the condenser cooling water.
- 05The problem
Polished condensate smells after a few days in storage.
What we doImprove the biological stage of the CPU, add carbon filtration and controlled disinfection, and size storage so water is used within a short time.
- 06The problem
Evaporator cleaning drains crash the biology every time.
What we doRoute caustic and acid cleaning solutions to a separate neutralisation tank and bleed them slowly into the equalisation tank.
What we offer
What Rispri does for sugar mills.
Effluent and condensate testing
BOD, COD, solids, oil and grease, TDS and nutrients in our NABL-accredited lab, before design and through the season.
Testing services →Sugar mill ETP and CPU
Anaerobic and aerobic ETPs and condensate polishing units, designed, built, commissioned and run.
Effluent treatment plants →Sugar processing chemicals
Juice clarification flocculants, evaporator and pan scale inhibitors, condenser cooling water treatment and ETP chemicals, with seasonal dosing.
Water treatment chemicals →Press mud biogas and Bio-CNG
Press mud CBG plants for SATAT, with digestate made into organic manure.
Biogas and Bio-CNG →OCEMS and water metering
Online effluent monitoring connected to the boards, and CGWA-compliant flow metering.
Smart water management →Reuse and ZLD
Filtration, RO and evaporation where your consent asks for zero discharge.
ZLD plants →Buying guide
What to ask before you buy a sugar mill ETP.
Use these questions with any supplier, including us.
- Was the design based on samples taken during crushing? Off-season samples tell you nothing about the real load.
- Are condensate and process effluent kept separate? And what happens to each stream.
- How is the plant restarted each season? Ask for a written start-up procedure and the time it takes to reach the outlet limits.
- What happens to the biogas? Boiler, flare or Bio-CNG, and who is responsible for gas safety.
- Which outlet values are guaranteed? BOD, suspended solids and oil and grease in writing, against my consent and the volumetric cap.
- How much condensate will be reused, and for what? Quality targets for each use, not only a volume.
- Where does the sludge go? Drying beds, a filter press, or mixing into press mud compost.
- Who runs it? Trained operators, chemicals, OCEMS upkeep and monthly NABL test reports.
Why Rispri
From cane water to reuse water, one team.
Our own NABL lab
We test your effluent and condensate before design and certify the outlet after start-up.
Engineering since 1999
1,498+ plants and turnkey projects and 499+ clients across industry, hotels, hospitals and cities.
Chemicals in house
Sugar processing, cooling water and ETP chemicals supplied and dosed by the same team that runs the plant.
Research partners
We work in collaboration with IIT Bombay, IIT Kharagpur and ICT Mumbai on water recovery and low-cost evaporation.
Questions
Sugar mill effluent treatment FAQs.
What is a sugar mill effluent treatment plant?
It is a treatment plant for the wastewater from cane milling, the boiling house, equipment washing and cooling circuits of a sugar factory. It usually combines screening, oil removal, equalisation with pH correction, an anaerobic reactor, aerobic treatment and filtration, so that the water meets the sugar industry standard or can be reused.
Why is sugar industry wastewater so polluting?
It carries sucrose and other sugars from spilt juice, syrup and molasses, which bacteria consume very quickly. That gives a BOD typically in the range of 1,000 to 2,500 mg/L, and the effluent turns acidic and smells within hours if it stands. Released untreated, it strips oxygen from rivers and kills fish.
What are the CPCB standards for sugar mill effluent?
The sugar industry standard under the Environment (Protection) Rules, 1986 sets BOD at 30 mg/L and suspended solids at 100 mg/L for discharge to inland surface water, with higher values for land irrigation, plus pH and oil and grease limits. The 2016 revision also caps how much wastewater may be generated per tonne of cane crushed. Your consent may be stricter.
What is a condensate polishing unit in a sugar mill?
A condensate polishing unit (CPU) treats the surplus condensate from the evaporators and pans so it can be reused. It cools the condensate, removes the small amount of sugar and volatile organics biologically, and filters it through sand and activated carbon. The polished water replaces fresh water for cooling make-up, washing and some process uses.
Can a sugar mill run without fresh water?
Close to it. Cane is about 70 per cent water, and most of that is recovered as condensate in the boiling house. With good condensate polishing, reuse of treated effluent and tight water management, many mills reduce fresh water intake to start-up and small top-ups.
How is the ETP restarted after the off-season?
The bacteria starve when there is no effluent for several months. Good practice is to keep the anaerobic sludge alive with occasional feeding, re-seed the aeration tanks with active sludge or cow dung slurry before crushing, and increase the load gradually over two to four weeks while testing BOD daily and dosing nutrients.
What is press mud and how is it used?
Press mud, or filter cake, is the mud removed when cane juice is clarified, and it amounts to about 3 to 4 per cent of the cane crushed. It is rich in organic matter and nutrients, so it is composted into manure, often with distillery spent wash, or used as feedstock for compressed biogas plants under the SATAT scheme.
Is OCEMS mandatory for sugar mills?
Yes. Sugar is one of the 17 categories of highly polluting industries that CPCB requires to install online continuous effluent and emission monitoring systems connected to CPCB and the state board.
How much does a sugar mill ETP cost?
As an indication, an anaerobic plus aerobic ETP of 500 to 1,000 KLD for a 2,500 to 5,000 TCD mill costs about ₹1.2 to 3.5 crore for equipment and installation, excluding civil works and land. A separate condensate polishing unit adds roughly ₹60 lakh to ₹2.5 crore depending on its size. We price after testing.
Can treated sugar mill effluent be used for irrigation?
Yes, if it meets the land-irrigation limits in the sugar standard and your consent, and the board allows it. Many mills irrigate their own or nearby cane fields with treated effluent, but they must avoid ponding and run-off and keep records of quantity and quality.
Which chemicals does a sugar mill use for water and process treatment?
Common ones are flocculants for juice clarification, scale inhibitors for evaporators and vacuum pans, biocides and dispersants for condenser cooling water, boiler treatment chemicals, and urea, phosphate and pH chemicals for the ETP.
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