INDUSTRIES / FERTILIZERS
Fertilizer plant wastewater treatment
that recovers ammonia instead of discharging it.
Fertilizer effluent is not about BOD. It is about nitrogen in ammonia, urea and nitrate form, and in phosphatic plants about fluoride, phosphate and acidity. We test your streams in our NABL-accredited laboratory, then design the stripping, biological and chemical treatment that meets your consent and sends ammonia and water back into the process.
In short
How fertilizer plant wastewater is treated.
Fertilizer plant wastewater is treated stream by stream, because each fertiliser process leaves a different pollutant. In nitrogenous plants (ammonia and urea), process condensate carrying ammonia and urea is treated in a hydrolyser-stripper, which breaks urea down to ammonia and carbon dioxide and strips them out for return to the process; the cleaned condensate is reused as boiler or cooling water. Remaining ammonia in mixed effluent is removed by air or steam stripping or biological nitrification and denitrification. In phosphatic plants, acidic gypsum pond and scrubber water is treated with lime to precipitate fluoride and phosphate. Fertiliser plants must meet CPCB's fertiliser industry standards under the Environment (Protection) Rules, 1986, and run online monitoring as one of the 17 highly polluting categories.
- 50mg/L
- Ammoniacal nitrogen limit for discharge to inland surface water under the general standards
- 2.0mg/L
- Fluoride limit in the general standards for inland surface water
- ~5t
- Phosphogypsum produced per tonne of P₂O₅ in wet-process phosphoric acid
- 17categories
- Highly polluting industries required to run OCEMS; fertiliser is one
Where it comes from
Where does fertilizer plant wastewater come from?
Indian fertiliser plants fall into two broad groups. Nitrogenous plants make ammonia from natural gas or naphtha and convert it into urea, ammonium nitrate or ammonium sulphate. Phosphatic and complex plants make phosphoric acid from rock phosphate and sulphuric acid, then DAP, NPK and SSP. Many complexes do both.
| Source | Plant | What it adds to the effluent |
|---|---|---|
| Ammonia plant process condensate | Condensed from the synthesis gas after reforming and shift conversion | Dissolved ammonia, carbon dioxide and methanol; usually stripped and reused as boiler feed |
| Urea plant process condensate | Water formed in the urea reaction and recovered from evaporation and vacuum sections | Ammonia, carbon dioxide and urea at percent-level concentrations before treatment |
| Prill tower and granulator scrubbers | Urea dust and ammonia scrubbed from exhaust air | Urea solution and ammonia, usually returned to the process |
| Cooling tower blowdown | Large cooling circuits across ammonia, urea and acid plants | TDS, hardness, treatment chemicals; ammonia where there are process leaks |
| Demineralisation plant regeneration | Ion exchange regeneration with acid and caustic | Acid and alkali, high TDS |
| Phosphoric acid scrubbers | Gases from reaction and concentration contain fluorine compounds | Fluosilicic acid and fluoride, acidity |
| Gypsum pond water | Water draining from phosphogypsum stacks and the slurry used to transport gypsum | Strongly acidic, high fluoride, phosphate, sulphate and some metals |
| Floor washing and spills | Product handling, bagging and storage areas | Ammonium, nitrate, urea, phosphate and solids |
Typical effluent characteristics
| Parameter | Typical character | Why it matters |
|---|---|---|
| Ammoniacal nitrogen | Tens to several hundred mg/L in combined effluent; far higher in untreated condensate | Toxic to fish as free ammonia; consumes oxygen in rivers when it nitrifies |
| Urea | Present wherever urea condensate or spills reach the drain | Hydrolyses to ammonia in drains and in the receiving water; counted in total Kjeldahl nitrogen |
| Nitrate | High in ammonium nitrate and nitrophosphate plants, and after nitrification | Limited in discharge; a drinking water concern if it reaches groundwater |
| pH | Alkaline in nitrogenous streams; strongly acidic in phosphatic streams | Decides how much ammonia is free (high pH) and how much lime phosphatic water needs |
| Fluoride | Very high in gypsum pond and scrubber water | Strict discharge limit; fluorosis risk if it reaches groundwater |
| Phosphate | High in phosphatic plants | Causes algal growth in lakes and rivers |
| TDS | High in blowdowns and regeneration waste | Limits reuse and decides whether RO and evaporation are needed |
| Oil and grease, metals | From compressors and older cooling water programmes | Chromium and zinc from cooling water treatment are regulated |
Unlike most industries, fertiliser plant pollutants are mostly product. Ammonia, urea and phosphate in the drain are fertiliser that was made and then lost. That is why the best treatment for this sector starts with recovery inside the plant.
Standards and rules
Which standards apply to fertilizer effluent?
The Environment (Protection) Rules, 1986 contain industry-specific standards for the fertiliser industry, with separate schedules for straight nitrogenous, straight phosphatic and complex fertiliser plants. They cover parameters such as pH, ammoniacal and total Kjeldahl nitrogen, free ammonia, nitrate, phosphate, fluoride, suspended solids, oil and grease, and, for nitrogenous plants, cyanide, arsenic, vanadium and chromium. Your consent states the exact values. For reference, the general standards for discharge to inland surface water (Schedule VI) are below; the fertiliser standards are built around similar limits.
| Parameter | General standard |
|---|---|
| pH | 5.5 to 9.0 |
| Ammoniacal nitrogen (as N) | 50 |
| Total Kjeldahl nitrogen (as N) | 100 |
| Free ammonia (as NH₃) | 5.0 |
| Nitrate nitrogen | 10 |
| Dissolved phosphates (as P) | 5.0 |
| Fluoride (as F) | 2.0 |
| Total suspended solids | 100 |
| Oil and grease | 10 |
| Hexavalent chromium | 0.1 |
Treatment scheme
How is ammonia removed from fertilizer effluent?
The scheme we start from treats strong streams at source and only the remainder in a central ETP. Mixing urea condensate, gypsum water and blowdowns in one tank makes every step harder.
- 1
Segregate
Keep urea and ammonia condensates, phosphatic acid water, cooling and boiler blowdown, and floor washings in separate collection systems with flow metering on each.
- 2
Hydrolyse and strip urea condensate
In a hydrolyser-stripper, urea is broken down to ammonia and carbon dioxide at high temperature and pressure with steam, and both are stripped out and returned to the urea synthesis. The treated condensate is low enough in urea and ammonia to be reused as boiler feed after polishing.
- 3
Strip ammonia from mixed effluent
The pH is raised to about 11 with lime or caustic so ammonia is in its free form, and it is stripped with air in a packed tower or with steam. Steam stripping lets the ammonia be recovered as aqueous ammonia; air stripping needs an acid scrubber so the ammonia is not simply moved into the air.
- 4
Biological nitrification and denitrification
For lower ammonia levels, bacteria convert ammonia to nitrate in an aerated tank (nitrification), then nitrate to nitrogen gas in an anoxic tank (denitrification). Fertiliser effluent has little carbon, so a carbon source and alkalinity are usually dosed.
- 5
Lime treatment for fluoride and phosphate
Acidic phosphatic water is neutralised with lime in two stages. Calcium fluoride and calcium phosphate precipitate, settle in a clarifier and are dewatered. A polishing step with alum or activated alumina is added where very low fluoride is needed.
- 6
Polish and reuse
Filtration, then RO where TDS allows, so the water returns to cooling towers and DM plant feed instead of a drain.
Nitrogen removal options compared
| Method | Best for | Watch-outs |
|---|---|---|
| Hydrolyser-stripper | Urea plant process condensate, with recovery of ammonia and CO₂ | High-pressure steam equipment; performance falls if the hydrolyser runs short of residence time or temperature |
| Steam stripping | Strong ammonia streams where ammonia can be recovered | Steam cost; scaling at high pH |
| Air stripping with acid scrubber | Moderate ammonia, with ammonium sulphate recovered in the scrubber | Lime scaling of packing; poor in cold weather; must not just release ammonia to air |
| Nitrification and denitrification | Residual ammonia and nitrate to low levels | Nitrifying bacteria are slow and sensitive to pH, temperature and toxic shocks; carbon source needed |
| Ion exchange or selective adsorbents | Polishing low ammonia in reuse water | Regeneration waste must be handled |
| Breakpoint chlorination | Emergency polishing of small residual ammonia | Chemical cost and chlorinated by-products; not for routine bulk removal |
Our NABL-accredited laboratory tests ammoniacal nitrogen, TKN, urea, nitrate, free ammonia, fluoride, phosphate, TDS and metals stream by stream, so you treat the source, not the whole drain.
Reuse and recovery
Recover ammonia, reuse water, use the gypsum.
A fertiliser complex can return most of its nitrogen and much of its water to the process. Recovery usually pays better than treatment.
Ammonia and urea
Hydrolyser-strippers return ammonia and CO₂ from urea condensate to synthesis. Steam strippers recover aqueous ammonia from other strong streams, and acid scrubbers on air strippers make ammonium sulphate that can go back into product.
Process condensate as boiler feed
Treated ammonia and urea condensates are low in dissolved salts. After polishing, typically by mixed-bed ion exchange, they are reused as boiler feed water, saving both water and DM plant regeneration chemicals.
Cooling tower blowdown
Cooling towers are the largest water users in most fertiliser plants. Better cooling water chemistry raises cycles of concentration and cuts blowdown; the remaining blowdown can be treated by RO and reused. RO reject is then evaporated where the consent requires zero liquid discharge, and our non-thermal RCD vaporiser evaporates it with air and waste heat at about ₹80 to 160 per cubic metre, against an estimated ₹430 to 1,070 in a steam MEE.
Phosphogypsum and fluorine
Phosphogypsum can be used in cement, gypsum board and as a soil amendment where it meets the applicable quality requirements. Fluorine from phosphoric acid scrubbers can be recovered as fluosilicic acid or its salts instead of being neutralised as waste.
Cost
How much does fertilizer effluent treatment cost?
For fertiliser plants, the cost depends less on flow than on how much nitrogen and fluoride must be removed and how much is recovered. Use these ranges for the water-side packages; process units such as hydrolyser-strippers are usually part of the licensor's scope.
| Plant | Typical scope | Indicative cost* |
|---|---|---|
| Ammonia stripping unit, 100 to 500 KLD | pH adjustment, packed stripping tower, acid scrubber, controls | ₹80 lakh to ₹4 crore |
| Biological nitrogen removal ETP, 500 to 2,000 KLD | Equalisation, anoxic and aerobic tanks, clarifier, carbon and alkalinity dosing | ₹3 to 12 crore |
| Fluoride and phosphate removal, 200 to 1,000 KLD | Two-stage lime treatment, clarifiers, sludge dewatering | ₹1 to 5 crore |
| Cooling blowdown recovery, per 500 KLD | Pretreatment, UF and RO for reuse | ₹2.5 to 6 crore |
*Indicative 2026 ranges for equipment, electricals and installation, excluding land, civil works and taxes. Nitrogen and fluoride loads, materials of construction for acidic streams, and the level of reuse change the figure a lot, so we price only after testing. Running costs are dominated by steam or power for stripping, lime and sludge handling, and RO cleaning.
What drives capital cost
- Nitrogen and fluoride loads
- Recovery or destruction of ammonia
- Corrosion-resistant materials
- Reuse and ZLD requirements
- Segregation of existing drains
What drives running cost
- Steam for strippers and hydrolysers
- Lime, acid and carbon source dosing
- Aeration power for nitrification
- Gypsum and fluoride sludge handling
- RO chemicals and membranes
Where plants lose money
- Product lost to drains as ammonia and urea
- Condensate not reused as boiler feed
- Low cooling tower cycles
- Mixing acidic and alkaline streams
- Stripped ammonia released to air
We review your cooling water chemistry, supply treatment programmes that raise cycles, and design blowdown recovery so less water is drawn and discharged.
Troubleshooting
Common fertilizer ETP problems, and how we fix them.
- 01The problem
Ammoniacal nitrogen at the outlet keeps crossing the limit.
What we doTest drains stream by stream to find the leak, often a urea condensate or scrubber bypass, fix it at source, then size stripping or biological removal for what remains.
- 02The problem
Nitrification stops after a shock load or in winter.
What we doAdd equalisation, control pH and alkalinity, keep sludge age long enough for nitrifiers, and protect the tank from toxic streams.
- 03The problem
Stripping tower packing scales up with lime.
What we doSettle lime solids before the tower, consider caustic for pH adjustment, and set acid cleaning schedules.
- 04The problem
Fluoride after lime treatment is still above the limit.
What we doOptimise the two-stage pH profile and settling time, add an alum or activated alumina polish, and check that clarifier carry-over is not the cause.
- 05The problem
Gypsum pond seepage is raising fluoride in nearby wells.
What we doTest groundwater around the stack, collect and treat leachate, and support lining and run-off control in line with CPCB's phosphogypsum guidelines.
- 06The problem
Cooling tower blowdown is high and the RO fouls.
What we doRework the cooling water programme, add suitable pretreatment ahead of RO, and supply antiscalants and cleaning chemicals tested on your water.
What we offer
What Rispri does for fertilizer plants.
Nitrogen and fluoride testing
Ammoniacal nitrogen, TKN, nitrate, fluoride, phosphate and metals in our NABL-accredited lab, including groundwater around gypsum stacks.
Testing services →Fertilizer ETPs
Ammonia stripping, biological nitrogen removal and lime treatment for fluoride and phosphate.
Effluent treatment plants →Non-thermal evaporator
RCD vaporisers that evaporate RO reject with air and waste heat instead of steam.
Non-thermal evaporators →OCEMS
Online monitoring of pH, ammonia, fluoride and flow connected to CPCB and the state board.
Smart water management →Cooling and boiler chemicals
Cooling water, boiler, RO and effluent treatment chemicals matched to your water.
Water treatment chemicals →Buying guide
What to ask before you buy a fertilizer ETP.
Use these questions with any supplier, including us.
- Was every stream tested separately? A composite sample hides where the nitrogen comes from.
- Is ammonia recovered or destroyed? And if stripped with air, where does it go.
- How does the biology cope with shocks? Equalisation, pH control and a recovery plan.
- Which outlet values are guaranteed? Ammoniacal nitrogen, TKN, nitrate, fluoride and phosphate in writing, against my consent.
- Are the materials right for acidic, fluoride-bearing water? Linings, pumps and instruments.
- What happens to the sludge? Calcium fluoride and gypsum sludge handling and authorisation.
- How much water will be reused? And for which uses.
- Who maintains OCEMS and the analysers? Calibration, spares and data upkeep.
Why Rispri
Treatment that starts at the source.
Our own NABL lab
Stream-by-stream testing before design and outlet certification after start-up.
Engineering since 1999
1,498+ plants and turnkey projects and 499+ clients across industry and cities.
Chemicals in house
Cooling, boiler, RO and effluent chemicals from the same team that designs the plant.
Research partners
We work in collaboration with IIT Bombay, IIT Kharagpur and ICT Mumbai on water recovery and evaporation.
Questions
Fertilizer plant wastewater FAQs.
What pollutants are in fertilizer plant wastewater?
Nitrogenous plants discharge ammonia, urea and sometimes nitrate, plus cooling and boiler blowdown. Phosphatic plants add acidity, fluoride, phosphate and sulphate from phosphoric acid production and gypsum ponds. Metals such as chromium and zinc can come from cooling water treatment.
How is ammonia removed from industrial effluent?
Strong ammonia is removed by raising the pH to about 11 and stripping it with air or steam, ideally recovering it as aqueous ammonia or ammonium sulphate. Lower levels are removed biologically by nitrification and denitrification. Ion exchange or selective adsorbents can polish reuse water.
How is urea plant process condensate treated?
In a hydrolyser-stripper. Urea is hydrolysed to ammonia and carbon dioxide with steam at high temperature and pressure, and both are stripped out and returned to synthesis. The treated condensate is then polished and reused as boiler feed water.
What is the discharge limit for ammonia in India?
Under the general standards of the Environment (Protection) Rules, 1986, ammoniacal nitrogen is limited to 50 mg/L and free ammonia to 5 mg/L for discharge to inland surface water. Fertiliser plants also have industry-specific standards, and their consent may set tighter values.
How is fluoride removed from phosphatic fertilizer effluent?
By lime treatment, usually in two stages, which precipitates calcium fluoride and calcium phosphate that settle in a clarifier. Where very low fluoride is needed, alum or activated alumina is used as a polishing step.
What is phosphogypsum and how is it managed?
Phosphogypsum is the calcium sulphate by-product of making phosphoric acid from rock phosphate, about five tonnes per tonne of P₂O₅. It is stored in lined stacks with run-off and leachate collection under CPCB guidelines, and can be used in cement, building materials and as a soil amendment.
Is OCEMS mandatory for fertilizer plants?
Yes. Fertiliser is one of the 17 categories of highly polluting industries that CPCB requires to install online continuous effluent and emission monitoring connected to CPCB and the state board.
Why does nitrification fail in fertilizer ETPs?
Nitrifying bacteria grow slowly and are sensitive to low pH, low temperature, high free ammonia and toxic shocks. Fertiliser effluent is also short of alkalinity and carbon. Equalisation, pH and alkalinity control, a long sludge age and protection from shock loads keep nitrification stable.
Can treated fertilizer plant water be reused?
Yes. Treated process condensate is commonly reused as boiler feed after polishing, and treated effluent and cooling blowdown can be recovered by RO for cooling make-up. Reuse reduces both fresh water intake and the discharge load.
How much does an ammonia stripping plant cost?
As an indication, an ammonia stripping unit of 100 to 500 KLD with an acid scrubber costs about ₹80 lakh to ₹4 crore for equipment and installation, excluding civil works. Ammonia load, recovery requirements and materials change the figure, so we price after testing.
Is air stripping of ammonia allowed?
Air stripping moves ammonia from water into air, so boards expect the off-gas to be scrubbed, normally with sulphuric acid to form ammonium sulphate. Releasing stripped ammonia without capture can breach air consent conditions and cause odour complaints.
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