Zero Liquid Discharge (ZLD)
As an essential and limited resource, water must be used wisely. In parallel the cost of obtaining fresh water is rising fast. As such, treatment of effluent as an opportunity to harvest water for re-use. Reducing pollution is no longer the end goal, but a key component in a broad strategy to re-cycle water, recover by-products and discharge zero harmful liquids to the environment.
Jord is committed to finding creative solutions that achieve Zero Liquid Discharge (ZLD) from effluent streams at a sensible cost. We combine a range of practical pre-treatments to modify the chemistry of effluents, followed by proven evaporation and crystallisation technology to separate clean water for re-cycle and to recover solid by products.
Molybdenum is a valuable by product of copper refining in Chile. When it is separated and purified for sale, an effluent that is a highly acidic mixture of ferrous and sodium sulphates is generated. Recently Jord and its technology partners developed a two part ZLD process to treat this effluent at affordable capital and operating costs.
Firstly the effluent is successively oxidised, treated with lime, softened and then neutralised in a process optimised by extensive testing. The resulting liquor is freed of troublesome ferritic compounds and is then evaporated in a forced circulation crystalliser to recover a by product salt that is mainly sodium chloride. The energy input required for evaporation is minimised using mechanical vapour recompression (MVR).
Wool scouring effluent is a complex emulsion of waxes, salts and particulate solids that is difficult to treat by conventional biological and chemical processes.
Jord designed and built a ZLD plant to screen and remove fibres and coarse particulates, then evaporate and concentrate the effluent. The fully integrated process produced a spadeable product that could be used as fertiliser and a clean water stream for recycle to the wool washing process.
Efficient evaporation was achieved in parallel falling film units each fitted with MVR for energy efficency.
Due to demanding specifications for the cleanliness of the wash water it was necessary to steam strip the condensate from evaporation to remove water soluble volatile components.
The turnkey plant included extensive storage to buffer effluent inflow and the return of clean water to process both a hot and cold stream. A dedicated boiler was provided to raise steam for stripping.
