Heavy Metals Removal Companies
Heavy metals treatment, precipitation, IX, sorbents, and membranes for lead, mercury, cadmium, chromium, arsenic.
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Buyer's guide
The buyer's guide to heavy metals removal
Heavy Metals Removal Technologies: Precipitation, Ion Exchange, and Membrane Processes
Heavy metals in industrial wastewater (lead, cadmium, chromium, mercury, arsenic, nickel, zinc, copper) are removed by chemical precipitation, ion exchange, adsorption, or membrane processes. Chemical precipitation raises pH to 8.5 to 11 (lime, NaOH, or Na2S dosing) to form insoluble metal hydroxides, sulphides, or carbonates with residual concentrations of 0.05 to 0.5 mg per L for most metals.
Chromium (VI) requires reduction to Cr (III) at pH 2 to 3 using sodium bisulphite or ferrous sulphate before precipitation. US EPA Best Available Technology (BAT) for electroplating wastewater specifies effluent limits: Cd 0.69 mg per L, Cr 0.38 mg per L, Pb 0.69 mg per L, Hg 0.032 mg per L (40 CFR Part 413).
Ion exchange resins provide polishing to below 0.01 mg per L for most heavy metals. Chelating resins (iminodiacetic acid type) offer high selectivity for heavy metals over calcium and sodium, enabling treatment of high-TDS effluents where strong-acid cation exchange would be saturated by competing ions. Activated carbon is not effective for most dissolved metals but removes organic-metal complexes (e.g. EDTA-metal, amino-metal). Adsorbent media including iron oxide-coated sand, granular ferric hydroxide, and activated alumina achieve arsenic residuals below 10 micrograms per L (WHO and US EPA MCL). Fixed-bed adsorbers are designed at EBCT of 3 to 6 minutes for arsenic removal, with media regenerated by NaOH at pH 12 to 14.
Nanofiltration and reverse osmosis achieve removal of 95 to 99 percent of dissolved heavy metals by size exclusion and charge repulsion. NF is selective for divalent ions (90 to 98 percent rejection of Pb2+, Cd2+, Cu2+) while passing monovalent ions (Na+, Cl-); this enables concentration of metals for recovery while producing low-TDS permeate for reuse. Electrocoagulation (EC) applies sacrificial iron or aluminium electrodes to generate coagulant in-situ, achieving metals removal to below discharge limits without chemical dosing; capital cost $50,000 to $500,000 for 10 to 1,000 m3 per day capacity. Zero-valent iron (ZVI) reactive barriers treat groundwater metals and chlorinated solvent plumes at contaminated sites at low operating cost.
Frequently asked questions
What is the most effective method for removing heavy metals from water?
For industrial wastewater with metals above 10 mg per L, chemical precipitation (lime or NaOH to pH 9 to 11) is the most cost-effective first step, reducing concentrations to 0.5 to 2 mg per L. For polishing to below 0.1 mg per L (discharge or reuse standards), follow with: ion exchange (chelating resin, achieves below 0.01 mg per L), adsorption media (granular ferric hydroxide or iron-oxide media for arsenic below 10 micrograms per L), or nanofiltration (95 to 99 percent rejection). For low-concentration influents (0.1 to 10 mg per L), direct ion exchange or adsorption may be more economic than two-stage precipitation plus polishing. Emerging electrochemical methods (electrocoagulation, electrodialysis) are gaining adoption for selective metals recovery and zero liquid discharge applications.
What are the discharge limits for heavy metals in industrial wastewater?
US EPA effluent limits (40 CFR Part 413, Electroplating) in mg per L: cadmium 0.69, chromium total 0.38 (Cr6+ 0.05), copper 1.2, lead 0.69, mercury 0.032, nickel 1.9, silver 0.43, zinc 2.6 (30-day average limits for POTW discharge). EU Industrial Emissions Directive (2010/75/EU) and associated BAT Conclusions set sector-specific limits; non-ferrous metals sector BAT-AEL: nickel 0.5 mg per L, zinc 1.0 mg per L, lead 0.3 mg per L. UK Environment Agency regulated limits are set in discharge consents and typically align with EU BAT-AEL values. WHO Drinking Water Guidelines (2017) are relevant for treated water: arsenic 10 micrograms per L, lead 10 micrograms per L, mercury 6 micrograms per L, cadmium 3 micrograms per L.
How is chromium removed from wastewater?
Chromium exists in two forms requiring different treatment. Cr(VI) (hexavalent, chromate and dichromate, highly toxic) must first be chemically reduced to Cr(III) (trivalent, far less toxic) at pH 2 to 3 using sodium metabisulphite, ferrous sulphate, or SO2 gas. The reduction reaction (Cr6+ + 3 Fe2+ yields Cr3+ + 3 Fe3+ in alkaline rearrangement) is complete within 5 to 15 minutes at pH 2 to 3. Then pH is raised to 8.5 to 9 with lime to precipitate Cr(III) as Cr(OH)3 (s); residual Cr after precipitation is typically 0.05 to 0.2 mg per L. Sludge from chromium precipitation contains Cr(OH)3 and is classified as hazardous waste in most jurisdictions. Ion exchange with strong-acid cation resin further polishes Cr(III) to below 0.01 mg per L.
Can heavy metals be recovered and recycled from wastewater?
Yes, for sufficiently concentrated waste streams. Selective ion exchange using chelating resins allows metal-rich eluates to be recovered and sold as metal salt solutions or processed by electroplating suppliers. Nickel recovery from electroplating rinse water by evaporator concentration and crystallisation produces nickel sulphate (minimum 98 percent purity) for direct reuse. Copper recovery by cementation (scrap iron addition to acidic Cu2+ solution, Cu deposits as metal) is used in printed circuit board manufacturing; copper purity 85 to 90 percent is achievable. Lead-acid battery wastewater lead recovery by electrowinning achieves 99.99 percent purity lead. Economic recovery thresholds: copper above 100 mg per L, nickel above 500 mg per L, gold above 0.5 mg per L are typically worth concentration and recovery versus chemical precipitation and landfill disposal.
Illustrative scenario · Surface finishing
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A metal finishing company in the West Midlands operating nickel electroplating and chromium plating lines generated 150 m3/day of mixed rinse water containing Cr(VI) at 15 to 80 mg/L, Ni at 20 to 60 mg/L, and Zn at 5 to 25 mg/L. The company held a Trade Effluent Consent to sewer with limits of Cr total 1 mg/L, Ni 2 mg/L, and Zn 3 mg/L, which it was regularly breaching. The EA had issued an enforcement notice requiring compliance within 6 months.
- Approach
- Installed a three-stage treatment system: (1) Cr(VI) reduction at pH 2.5 using sodium metabisulphite (residence time 20 minutes, ORP control to below -250 mV); (2) pH adjustment to 9.5 with lime for co-precipitation of Cr(III), Ni, and Zn hydroxides in a lamella settler; (3) polishing by chelating ion exchange resin (iminodiacetic acid type) to achieve Ni below 0.1 mg/L. Sludge dewatered by filter press to 35 percent solids, classified as hazardous waste, and disposed to licensed landfill.
- Outcome
- Trade Effluent Consent compliance achieved: Cr total 0.12 mg/L (limit 1 mg/L), Ni 0.08 mg/L (limit 2 mg/L), Zn 0.4 mg/L (limit 3 mg/L) at the 95th percentile. EA enforcement notice closed. Annual chemical cost for the treatment system (NaHSO3, lime, acid for IX regeneration) was 28,000 GBP. Sludge disposal 18 tonnes per year at 450 GBP per tonne. Capital cost 320,000 GBP, payback 4.2 years versus the Trade Effluent Consent penalty tariff.
Questions to ask shortlisted providers
5
- 01
What characterisation data do you need from us (flow, heavy metal concentrations, pH range, organic load, and complexing agents), and how will your design handle the variability in our batch discharge pattern?
Heavy metals treatment performance depends critically on the speciation and complexing agents in the wastewater. EDTA-complexed metals (common in circuit board and PCB processes) do not precipitate at standard pH because the metal-EDTA complex is more stable than the metal hydroxide. Understanding whether complexing agents are present and designing pretreatment accordingly is essential; a designer who does not ask about complexing agents has not done adequate characterisation.
- 02
What Cr(VI) reduction method do you propose, and how will you control ORP (oxidation-reduction potential) and pH during the reduction stage?
Cr(VI) reduction is the most failure-prone stage of chromium treatment. Incomplete reduction (ORP not reached, insufficient residence time, pH too high) results in Cr(VI) passing to the precipitation stage where it does not precipitate and breaches the consent limit. ORP online monitoring with automatic sodium metabisulphite dosing, and pH control at 2 to 3, are the minimum controls. Manual batch dosing without online ORP control is inadequate for regulatory compliance.
- 03
What sludge production rate (kg dry solids per m3 of wastewater), cake solids content (percent), and disposal route have you assumed in the cost model?
Heavy metals sludge disposal is a hazardous waste cost that can equal the annual chemical treatment cost. Design assumptions for sludge production rate (varies with metal concentration, pH, and lime dose) and cake solids (12 to 25 percent for belt press, 25 to 35 percent for filter press) directly affect the disposal cost. A design that underestimates sludge production by 50 percent creates a disposal budget overrun within the first year of operation.
- 04
What ion exchange resin do you propose for polishing, and have you tested it against our wastewater matrix to confirm selectivity for Ni and Cr over the competing cations (Ca, Mg, Na) present in our water?
Chelating resins for heavy metal polishing are highly selective when properly matched to the wastewater matrix. Strong-acid cation resins in hard water will be saturated by Ca and Mg before removing sufficient Ni, requiring very frequent regeneration and adding chemical cost. A bench-scale or pilot test of the specific resin on your actual wastewater (after precipitation, simulating the actual IX feed) is required before committing to the design.
- 05
How will the hazardous waste sludge be characterised, classified, and disposed of, and do you have an agreement with a licensed hazardous waste carrier and disposal facility for the anticipated sludge volume?
Heavy metal hydroxide sludge from electroplating wastewater is classified as hazardous waste under the UK Hazardous Waste Regulations 2005. A pre-disposal waste characterisation test (WC test) is required to confirm the European Waste Catalogue code and leachate toxicity. Disposal must be with a licensed hazardous waste carrier and at a permitted facility. Failure to correctly classify and manifest hazardous waste is a criminal offence with unlimited fines.
What drives cost in this category
4
- Heavy metal concentration and flow rate
- Chemical precipitation costs scale directly with metal load (kg/day of heavy metals requiring treatment). A plant treating 150 m3/day at 50 mg/L Ni requires 7.5 kg/day Ni in sludge. At 2.5 kg NaOH per kg Ni precipitated, this requires 18.75 kg/day NaOH (approximately 10 GBP/day chemical cost). For the same flow at 5 mg/L Ni, chemical cost falls 90 percent. Accurate metal concentration data from representative sampling is the most important input to cost modelling.
- Cr(VI) specific pre-treatment step
- Chromium treatment requires an additional reduction step (sodium metabisulphite, ferrous sulphate, or SO2) before precipitation, adding 20 to 40 GBP per kg Cr(VI) removed in chemical cost. This makes chromate wastewater significantly more expensive to treat per m3 than nickel or zinc-only streams. An online ORP control system for the reduction step costs 8,000 to 20,000 GBP but prevents under-reduction events that cause consent breaches.
- Polishing stage for stringent discharge limits
- Chemical precipitation achieves Ni at 0.5 to 2 mg/L, which may satisfy some Trade Effluent Consents but not direct river discharge standards (typically 0.1 to 0.3 mg/L). Adding chelating ion exchange polishing to achieve below 0.1 mg/L adds 40,000 to 120,000 GBP in CAPEX and 15,000 to 40,000 GBP per year in regenerant chemicals and resin replacement. This cost must be weighed against the consent limit and enforcement risk.
- Sludge dewatering and disposal
- Filter press (25 to 35 percent cake solids) costs 30,000 to 80,000 GBP CAPEX for a small industrial plant; belt press (18 to 22 percent cake solids, lower operating cost) costs 50,000 to 120,000 GBP. Disposal cost is 300 to 600 GBP per tonne for hazardous waste landfill. For 18 tonnes per year of filter cake, disposal is 5,400 to 10,800 GBP per year. Investing in higher cake solids (filter press over belt press) reduces disposal cost by 30 to 50 percent: typically 2 to 4 year payback.
Key regulations and standards
4
- Water Industry Act 1991: Trade Effluent Consent Limits for Heavy Metals
- Trade Effluent Consent under the Water Industry Act 1991 Section 119 specifies discharge limits for heavy metals to public sewer. UK sewer consent limits for electroplating and surface finishing typically include: Cr total 1 to 5 mg/L, Cr(VI) 0.1 mg/L, Ni 2 to 5 mg/L, Zn 3 to 10 mg/L, Pb 1 to 2 mg/L, Cd 0.1 to 0.5 mg/L. Consents must be obtained before discharge; breach is a criminal offence. Consent conditions are reviewed and may be tightened when the sewerage undertaker conducts periodic consent reviews.
- Environmental Permitting Regulations 2016: IED Permit for Surface Treatment Facilities
- Surface treatment facilities (electroplating, anodising, phosphating) above thresholds in Schedule 1 of the Environmental Permitting Regulations 2016 require an Environmental Permit from the Environment Agency, applying IED BAT conclusions from the Surface Treatment with Solvents (STS) BREF and related sectors. BAT-AELs set discharge standards for heavy metals to water. EA environmental permits include wastewater monitoring and reporting requirements.
- UK Hazardous Waste Regulations 2005: Heavy Metal Sludge Classification
- Heavy metal hydroxide sludge from electroplating and surface finishing wastewater treatment is classified as hazardous waste under the UK Hazardous Waste Regulations 2005 (EWC code 19 08 13* for metal-bearing sludge). A pre-disposal waste characterisation test (WC3 for landfill acceptance) is required. Sludge must be transported by a licensed hazardous waste carrier with consignment notes per the Hazardous Waste (England and Wales) Regulations 2005. Disposal at a permitted hazardous waste facility only.
- REACH (UK REACH): Hexavalent Chromium as SVHC
- Hexavalent chromium (Cr(VI)) compounds (chromates, dichromates) are Substances of Very High Concern (SVHC) under UK REACH (retained EU REACH Regulation 1907/2006). Articles containing Cr(VI) above 0.1 percent by weight cannot be supplied to UK consumers without notification. Industrial uses of Cr(VI) in chrome plating require authorisation under REACH Annex XIV. The water treatment system must ensure Cr(VI) does not pass to the receiving environment and that Cr(VI) in process residues is correctly classified and managed.
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