Remove high ammonia from industrial effluents and convert it into valuable fertilizer-grade ammonium sulphate without biological nitrification.
Ammonia stripping is a physical-chemical process that removes dissolved ammonia (NH3/NH4+) from wastewater by shifting the equilibrium to gaseous NH3 through pH elevation and temperature, then stripping the gas with steam or air. The ammonia-rich gas is absorbed in sulphuric acid to produce ammonium sulphate, a marketable fertilizer. This process is ideal for high-strength ammonia streams (100-2,000 mg/L) where biological nitrification would be too slow, too expensive, or inhibited by other contaminants.
Purely physical-chemical – no activated sludge, no nitrification bacteria, no sensitivity to toxins or temperature.
Ammonium sulphate fertilizer (21-0-0 NPK) sold to agriculture, offsetting 15-30% of operating overheads.
Single-pass reduction from 500 mg/L to <5 mg/L in minutes, compared to days for biological nitrification.
Can use waste steam from boilers, evaporators, or WAO processes – zero additional energy requirement.
Step-by-step breakdown of the treatment process from influent to effluent.
Caustic soda (NaOH) or lime raises pH to shift ammonium equilibrium from NH4+ to volatile NH3 gas. Online pH control maintains setpoint within ±0.2.
Wastewater preheated by heat exchanger using stripped effluent or waste steam. Higher temperature increases NH3 partial pressure for faster stripping.
Packed tower (Raschig rings or structured packing) with counter-current steam or air flow. NH3 transfers from liquid to gas phase. 95-99% removal achieved.
Ammonia-rich gas enters absorption tower with sulphuric acid mist. Reaction: 2NH3 + H2SO4 → (NH4)2SO4. Product solution at 40% concentration crystallised to solid fertilizer.
Stripped effluent pH 10.5 readjusted to 7.0-8.0 with CO2 or sulphuric acid for discharge or downstream treatment. Residual ammonia <5 mg/L.
Explore the equipment components that make this process effective.
Packed tower with structured packing, 95% NH3 transfer efficiency, SS316 construction.
Plate heat exchanger recovering heat from stripped effluent to preheat influent.
NaOH and H2SO4 day tanks with metering pumps, online pH control.
H2SO4 mist absorption tower producing 40% ammonium sulphate solution.
Stripping ammonia from wet air oxidation effluent before RO polishing.
Ammonia 800-1,500 mg/L from coke production stripped to <15 mg/L.
High-ammonia process streams where advanced biological treatment is inhibited.
Ammonium sulphate byproduct sold to local farms as nitrogen fertilizer.
This treatment stage is engineered to achieve specific contaminant removal targets while providing stable, predictable performance across variable inlet conditions. Design parameters are calculated from wastewater characterisation data, regulatory requirements, and site-specific constraints including footprint, energy availability, and operator capability.
Design validated by CFD modelling and pilot testing to confirm performance guarantees.
Equipment selected for 20-year design life with minimal wearing parts and easy access.
Automated dosing and feedback control minimise reagent consumption and sludge production.
Online monitoring and data logging demonstrate continuous consent compliance.
| Design Flow | 10 – 5,000 m³/h (application specific) |
| Inlet Variability | Designed for 1:3 peak-to-average flow ratio |
| Removal Efficiency | 85 – 99% depending on target contaminant |
| Hydraulic Retention | Calculated from kinetic constants and safety factors |
| Power Consumption | 0.5 – 5.0 kWh/100 m³ (process dependent) |
| Chemical Dose | Auto-controlled based on online analysers |
| Sludge Production | 0.2 – 1.5 kg DS/kg contaminant removed |
| Materials | SS304, SS316L, or carbon steel with coating |
No treatment stage operates in isolation. This process is designed to receive conditioned influent from upstream stages and deliver effluent quality suitable for downstream processes. Hydraulic and organic loading rates are balanced across the complete treatment train to prevent bottlenecking and ensure overall plant efficiency. Our engineers model the complete flowsheet to optimise Capital expenditure and Operating expenditure across the plant lifecycle.
Screening, equalisation, and pre-treatment protect this stage from damage and overload.
Effluent quality ensures downstream biology, filtration, or disinfection performs optimally.
Reject streams, filtrate, and centrate are routed back to appropriate upstream points.
From Henry's Law to HTU/NTU — the engineering behind column sizing.
The fraction of total ammonia present as volatile NH3 (vs ionic NH4+) is governed by pH and temperature:
NH3 fraction = 1 / (1 + 10(pKa − pH))
where pKa = 0.09018 + 2729.92/T (T in Kelvin). At 25°C, pKa ≈ 9.25. At pH 11, >98% is NH3; at pH 7, <1% is NH3.
Henry's Law constant for NH3 increases strongly with temperature:
| T (°C) | H (atm·m³/mol) | % NH3 at pH 10.5 |
|---|---|---|
| 20 | 1.7 × 10−5 | 94% |
| 40 | 3.8 × 10−5 | 94% |
| 60 | 7.5 × 10−5 | 94% |
| 80 | 1.3 × 10−4 | 95% |
Column height Z = HTU × NTU, where:
HTU = G / (KGa × P × A)
NTU = ∫ (dY / (Y − Y*))
G = molar gas flow (kmol/h), KGa = overall mass transfer coefficient (kmol/m³/h/atm), P = total pressure (atm), A = column cross-section (m²), Y = gas-phase NH3 mole fraction, Y* = equilibrium mole fraction.
Typical design values for steam stripping of high-strength ammonia:
| Component | Conditions | Recommended Material | Alternative |
|---|---|---|---|
| Stripping column shell | pH 10.5–11, 60–80°C, NH3 | SS316L clad carbon steel | SS2205 duplex |
| Structured packing | High pH, erosion | SS316L | PTFE-coated SS |
| Absorption tower | H2SO4 mist, 40–60°C | SS316L / PTFE lined | Hastelloy C-276 |
| Heat exchanger (influent) | pH 10.5, scaling risk | SS316L plate | Titanium (if chlorides >1,000 mg/L) |
| Piping (NaOH) | 50% NaOH, ambient | Carbon steel | SS304 (for <40%) |
| Piping (H2SO4) | 93–98%, ambient | Carbon steel (passivated) | SS316L for dilute acid |
| Pumps | Caustic / hot ammonia | SS316L or Alloy 20 | Mag-drive for sealing |
Check pH is >10.5 at column inlet. Verify steam flow and temperature (>100°C superheated preferred). Inspect packing for fouling (CaCO3 scaling from hard water) or channeling. Packing pressure drop should be 5–15 mbar/m; higher indicates blockage.
Surfactants in coke-oven or chemical wastewater cause stable foam, raising pressure drop and carry-over. Install foam breaker spray nozzles at column top; consider antifoam dosing (polypropylene glycol, 5–20 ppm). Monitor differential pressure as early indicator.
Product concentration depends on H2SO4 flow and NH3 gas rate. If <35% w/w, increase acid stoichiometry to 1.05–1.10 mol H2SO4 / mol NH3. Check for acid dilution from condensate carry-over.
High-pH preheated wastewater precipitates calcium carbonate and magnesium hydroxide on heat exchanger plates. Maintain inlet pH <10.8 if hardness >300 mg/L CaCO3, or install softening pre-treatment. Schedule acid cleaning (5% citric) every 3–6 months.
| Cost Item | Typical (/kg N) | Notes |
|---|---|---|
| Caustic soda (NaOH) | 0.15–0.25 | pH 10.5–11.0; 3.5–4.5 kg/kg N |
| Sulphuric acid | 0.08–0.12 | 2.9 kg H2SO4 / kg N |
| Steam | 0.10–0.40 | If waste steam: near zero |
| Power (pumps, blowers) | 0.03–0.05 | 5–15 kWh/100 m³ |
| Labor & maintenance | 0.05–0.10 | Proportional to plant size |
| Total Operating expenditure | 0.40–0.90 | Before byproduct credit |
| Byproduct credit (NH4)2SO4 | −0.10–−0.25 | 21-0-0 fertiliser, –350/t |
| Net Operating expenditure | 0.25–0.70 | Highly variable by site |
| Factor | Stripping | Biological Nitrification |
|---|---|---|
| Capital expenditure (500 m³/d) | –1.5M | –2.0M |
| Operating expenditure (/kg N) | 0.25–0.70 | 0.40–0.80 |
| Start-up time | Hours | 2–6 weeks |
| Inhibitor sensitivity | None | High (heavy metals, phenols) |
| Sludge production | Minimal | 0.15–0.25 kg TSS/kg N |
| Byproduct | Fertiliser | None (N&sub2; gas) |
| Footprint | Compact | Large (aeration + clarifier) |
| Best inlet NH3 | 200–2,000 mg/L | <100 mg/L preferred |
Our engineers design and commission complete treatment systems including all equipment, automation, and commissioning support.
Our expertise spans multiple industries with sector-specific water treatment solutions.