SOLVIA LeachateX is a modular system for treating the leachate of municipal solid waste landfills. The leachate and the reverse osmosis concentrate are handled as separate streams: the concentrate is conditioned by lime and aeration, split by electrodialysis and sent to adaptive destruction under by-product control.
The development gathers into one controlled line what is usually installed as separate blocks: physico-chemical pre-treatment with coagulation and flotation, ultrafiltration, reverse osmosis, lime-and-aeration conditioning of the concentrate, electrodialysis separation of the streams and adaptive destruction of hard-to-treat pollutants. The osmosis permeate goes on to quality control, the concentrate into a separate accumulation and reaction tank, and the further route of treatment is set from analytical readings rather than once and for all.
It is meant for the leachate of municipal and household solid waste landfills and for the concentrates of membrane plants already in service. The build is block-modular or containerised, and the solution is deployed in three ways: as a new leachate treatment line, as a concentrate module tied into an existing membrane line without rebuilding it, and as a centralised point that receives concentrate delivered from other waste handling sites.
Landfill leachate is not domestic sewage. Its composition depends on the age of the landfill, on the waste it holds, on the season and the rainfall, on how far the organics have decomposed and on the pre-treatment already in place. Mature leachate from old landfills is more difficult still: a low BOD₅/COD ratio, a high concentration of ammonium nitrogen, high salinity, raised chlorides, manganese, calcium, magnesium, humic substances and organics that resist oxidation.
The usual scheme — screening, physico-chemical pre-treatment, ultrafiltration, reverse osmosis and concentrate disposal — does not remove the problem, it moves a large part of the load into the concentrate. Salts, ammonium nitrogen, manganese, organics, PFAS, residual antiscalants and chlorides end up there together. SOLVIA LeachateX is built on carrying the leachate and the concentrate onward as two different streams, each with a regime of its own.
Manganese is one of the awkward components of leachate, and in the osmosis concentrate it reaches high values. Once inside an electrodialysis module manganese oxidises and settles as MnO₂ on the cation-exchange membranes: the stack voltage rises, mass transfer worsens, the service life of the membranes shortens. Magnesium, heavy metals and ammonium nitrogen load the module in the same way, and the concentrate is therefore not fed to separation as it comes.
The conditioning comes before the separation. At pH 10.5–11.0 and with aeration, Mg(OH)₂, MnO₂ and the hydroxides of heavy metals settle out, while the ammonium nitrogen leaves the stream in part — by 30–70 %. The sludge is drawn off, and electrodialysis receives a stream without the bulk of what fouls membranes. Below 15 °C the lime-and-aeration unit is heated to 20–25 °C, otherwise reaction rates and aeration efficiency fall.
The return to a working regime is done in two steps. The first is CO₂ down to pH 8.0–8.5, the second CO₂ down to pH 5.0–5.5 or HCl down to pH 3.5–5.0 with a limit on the chloride gain. The choice of acid matters here: sulphuric raises the risk of CaSO₄ where calcium remains, so with a raised Ca²⁺ the H₂SO₄ is limited or ruled out. The stream then passes a 5–20 µm guard filter that takes off the suspended matter and the humic aggregates formed during acidification.
The electrodialysis module divides the conditioned concentrate into a low-chloride stream and a salt stream. The point of the division is that chlorides stand in the way of oxidative destruction of the organics: a high-chloride stream sent straight to anodic oxidation yields chlorates, perchlorates, monochloramine and adsorbable organic halides. The target in the low-chloride stream is below 500 mg/l at a conductivity above 1500 µS/cm, and where such a reduction costs too much energy the control unit switches to a partial reduction of chlorides with a larger share of plasma treatment.
The low-chloride stream goes to the adaptive destruction block, where the composition of the water decides between electro-Fenton oxidation, anodic oxidation, a combination of the two and plasma treatment, and where single stages are bypassed under a low organic load. Electro-Fenton breaks down the organics that resist oxidation and the organic complexes of metals, after which the stream is neutralised, the Fe(OH)₃ is filtered off and the residual H₂O₂ is decomposed.
Feed into the anodic zone is allowed only with iron and hydrogen peroxide under control — otherwise the BDD/Ti₄O₇ anodes are fouled. In the zone itself pH 8.0–9.5 is held and the chlorides, the current density, the chlorates, the perchlorates, the monochloramine and the AOX are watched, and above the set values the system lowers the current density, switches the regime or blocks the blending of the stream with the treated water.
After electrodialysis the salt stream is not blended with the treated water automatically but goes to a treatment of its own: ammonia stripping, work on PFAS, plasma or hydrothermal alkaline treatment, sorption, ion exchange, evaporation, crystallisation, storage or separate removal. Crystallisation is allowed only after toxicological control and a confirmed reduction of PFAS measured as total organic fluorine.
The ammonium nitrogen is taken out in stages. Part of it leaves at the lime-and-aeration step, and beyond that ammonia stripping, a membrane gas-liquid contactor, vacuum stripping or ion exchange are used. For the blended stream of osmosis permeate and the treated stream after destruction a final removal is provided at a reduction factor of no less than 98 %, and at a low temperature the membrane contactor is brought in, because classical stripping loses efficiency.
SOLVIA LeachateX is SOLVIA's own technological development in the treatment of landfill leachate and of reverse osmosis concentrates; it holds patent protection in Russia. The solution brings together physico-chemical pre-treatment, ultrafiltration, reverse osmosis, lime-and-aeration conditioning of the concentrate, electrodialysis separation, adaptive destruction, ammonium removal, PFAS control and treatment of the salt stream under one control system driven by analytical readings. Structural parameters, treatment regimes, reagent dosages, control algorithms and layout decisions are chosen for the individual site and are not disclosed in open materials.
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