Raw Water Quality Requirements For ALS2 Closed-Loop Recycling Systems
Water is a working resource in any compact precious-metals recovery plant. In an ALS2 closed-loop system, it supports separation, washing, cooling, cleaning and other process duties before being treated and returned for reuse. Its quality therefore affects equipment reliability, recovery performance, maintenance intervals and the volume of make-up water required.
The acidless approach removes the need for aggressive mineral acids, but it does not make water quality irrelevant. Suspended solids, dissolved salts, oils, hardness and trace metals can build up as the loop operates. A suitable feedwater programme keeps these contaminants within a controlled range and prevents gradual deterioration from becoming a production problem.
For Australian operators, the practical target is consistent, testable water rather than a single ideal laboratory result. A WEEE processor in Smithfield, Welshpool or the outer suburbs of Melbourne may receive highly variable feedstock, operate under water restrictions and rely on municipal water with changing seasonal characteristics. The ALS2 water circuit should be designed around those realities.
| Water characteristic | Practical target for initial design | Why it matters |
|---|---|---|
| pH | Approximately 6.5–8.5 | Protects pumps, tanks, seals and treatment media |
| Suspended solids | Preferably below 10 mg/L after pre-treatment | Limits fouling, sediment and blocked filters |
| Oil and grease | Non-detectable or near-zero | Prevents coating of surfaces and interference with treatment |
| Total hardness | Low to moderate, preferably below 100 mg/L as CaCO₃ | Reduces scale on heat exchangers and pipework |
| Chloride | Keep low and monitor concentration over time | Helps control corrosion and loop accumulation |
| Conductivity | Establish a site baseline and trend it continuously | Indicates dissolved-salt build-up |
| Dissolved metals | As low as practical, with copper, iron and zinc monitored | Prevents contamination and unwanted precipitation |
| Microbiological activity | Controlled, especially in warm storage tanks | Reduces biofilm, odour and filter loading |
These figures are sensible starting points for engineering and commissioning, not a substitute for the ALS2 equipment supplier’s specifications, local water analysis or a site-specific mass balance.
Why Feedwater Consistency Matters
Closed-loop recycling systems repeatedly use the same water, so contaminants that leave with evaporation, sludge or filter backwash may remain in the circuit. A small amount of chloride or hardness in incoming water can become significant after many cycles. The risk is greater where the plant has low discharge rates and high reuse targets.
Consistent water supports stable separation conditions. It also makes troubleshooting easier: if conductivity, turbidity or pH changes unexpectedly, operators can connect the event to a clear cause such as a new e-waste batch, a failed filter or excessive make-up water. Without a reliable baseline, process issues can be mistaken for changes in the feed material.
Australian sites often receive mains water that is perfectly suitable for general industrial use but unsuitable for unrestricted recirculation. Perth water can be relatively hard, while regional supplies may vary considerably after drought, heavy rain or changes in bore-water use. A laboratory report taken once at installation is useful, but scheduled retesting is essential.
Key Physical And Chemical Parameters
Suspended solids should be removed before water enters sensitive parts of the loop. Fine particles from shredded printed circuit boards, dust, glass fibre, solder residue and treatment sludges can settle in tanks or load cartridge filters quickly. A settling stage, bag filter, disc filter or equivalent pre-treatment may be appropriate, depending on particle size and flow.
Oil, grease and organic residues deserve special attention. E-waste can arrive with lubricants, plastic residues, cutting fluids, packaging contamination or workshop grime. Even a thin oily film can affect sensors, pumps and filtration media. Incoming water should also be checked for chemical oxygen demand, surfactants and other organic matter where the site has mixed industrial activities.
pH should remain within the operating range specified for the ALS2 plant. Rapid swings can indicate chemical dosing faults, contamination from a new feedstock or incorrect cleaning practice. Operators should use calibrated instruments and take samples from both the incoming water and the circulating loop, since the two results may differ substantially.
Dissolved Salts, Hardness And Corrosion Risk
Hardness is mainly associated with calcium and magnesium. When concentrated or heated, these minerals can form scale on pipe walls, tanks, heat exchangers and dosing equipment. Scale reduces heat transfer and flow capacity, while deposits can shelter fine particles and microorganisms. Softening, reverse osmosis or controlled blowdown may be considered when hardness is high.
Conductivity is one of the simplest ways to identify dissolved-salt accumulation. It does not identify a particular contaminant, so it should be read alongside chloride, sulphate, alkalinity and selected metals. A rising trend is often more useful than a single number. Establish the normal operating band during commissioning, then define investigation and alarm points.
Chloride deserves careful monitoring because it can contribute to corrosion in stainless steel components and fittings, particularly where oxygen, heat and deposits are present. Australian coastal locations such as Newcastle, Geelong and parts of Brisbane may also face salt-laden air, which can add an external corrosion burden around tanks and electrical cabinets. Good plant design separates water chemistry controls from environmental corrosion protection.
Metals And Contaminants From E-Waste
The water loop may encounter dissolved or particulate copper, iron, aluminium, zinc, nickel, lead and tin from electronic assemblies. Precious metals such as gold, silver, palladium and platinum are valuable process targets, but other metals can affect selectivity, sludge characteristics and downstream water treatment. Testing should therefore cover the full expected feedstock profile rather than focusing only on the saleable metals.
A representative sampling plan is more important than an occasional grab sample. Samples should be collected from make-up water, process return, clarified water and any concentrated waste stream. Use clean containers, preserve samples according to the laboratory’s instructions and record the material being processed at the time. This creates a traceable link between water chemistry and production behaviour.
Where water passes through a treatment stage, confirm that the treatment media are compatible with the expected contaminant load. Activated carbon, ion exchange, membrane systems and precipitation stages each respond differently to suspended solids, oil, pH and dissolved metals. Pretreatment can extend media life and reduce unexpected pressure loss.
Monitoring, Sampling And Control
A practical monitoring programme combines online instruments with laboratory verification. Online pH, conductivity, temperature, flow and turbidity measurements provide immediate warning of drift. Laboratory tests can then confirm alkalinity, hardness, chloride, sulphate, total dissolved solids, dissolved metals, oil and grease, and microbiological activity where necessary.
Sampling points should be accessible and clearly labelled. Avoid relying only on a tank surface sample, since solids may settle and contamination may stratify. A good procedure specifies whether the sample is taken before or after filtration, how long the loop has been operating and whether the sample represents normal production or a cleaning cycle.
The control system should record trends rather than isolated readings. A gradual increase in conductivity may call for partial replacement or improved purification, while a sudden turbidity spike could indicate a ruptured filter or an upset in upstream separation. Alarms should lead to defined operator actions, including isolation, retesting and inspection.
Digital records also need sensible access controls. Keep process instruments and plant networks separate from general browsing; even unrelated online entertainment services should never be accessed from control-system terminals. This is a basic safeguard for a facility where water-quality data, production records and safety functions depend on reliable industrial connectivity.
Australian Site Conditions And Compliance
Australian water management must account for local supply constraints. A plant in South Australia may need to minimise potable-water use, while a Queensland facility may need robust stormwater separation during intense rainfall. In Western Australia, bore water can have a different mineral profile from scheme water. Each site should test its actual source and confirm whether a rainwater or recycled-water supply is suitable for make-up duties.
Storage tanks should be protected from dust, insects, direct sunlight and uncontrolled stormwater entry. This matters in dry areas around Adelaide and inland New South Wales, where airborne dust can quickly increase filter loading. Tank vents, lids, bunding and overflow arrangements should be included in the design rather than added after commissioning.
Discharge and waste handling must align with the relevant state or territory requirements and the conditions imposed by the local water authority or trade-waste regulator. A Sydney operation, for example, may need approval for trade-waste discharge, while a remote facility may have tighter practical limits because disposal and laboratory services are less accessible. The water balance should identify evaporation, sludge, filter backwash, blowdown and any wastewater leaving the site.
Commissioning And Ongoing Optimisation
Before commissioning, analyse the proposed make-up water and compare it with the ALS2 supplier’s limits. Confirm the required treatment train, instrument ranges, sampling points and cleaning chemicals. The system should be flushed and inspected before production water is introduced, particularly where new pipework contains fabrication debris or passivation residues.
During the first operating period, establish a baseline under normal feedstock conditions. Record water consumption, conductivity, turbidity, pH, filter pressure drop, sludge generation and any visible scaling. Repeat the analysis after the loop has completed a representative number of cycles, since early make-up water results do not show how contaminants accumulate.
Operators should review the trend data alongside recovery performance and maintenance records. If a filter blocks faster after a particular feed category arrives, the response may involve better feed preparation rather than simply installing a larger filter. If hardness drives scale, a softener or revised blowdown strategy may be more efficient than repeated manual cleaning.
A controlled water-quality specification helps ALS2 deliver its environmental benefits in everyday operation. It reduces avoidable water consumption, supports stable precious-metal recovery and limits the transfer of contaminants into waste streams. For Australian recyclers, the right approach is to test the source, design for concentration effects and maintain the loop with disciplined monitoring.
Speak with the ALS2 technical team before finalising plant utilities, filtration or water-treatment equipment. Provide recent source-water results, expected feedstock, operating hours and local discharge conditions so the closed-loop system can be matched to the site from the start.