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Applications

  • Desalination
  • Effluent
  • Clean water
  • Biological

Desalination refers to the removal of salts and minerals from water. In recent years, reverse osmosis technology has dominated this sector.

Brackish water

Brackish water desalination technologies can be divided into two main groups: ion exchange and reverse osmosis. Ion exchange is the most widely applied and more economical for desalination of waters with a low salt content.

This market is currently dominated by reverse osmosis technology due to its favourable economics in the brackish water range.

PROXA has extensive experience in the use of brackish water membranes for the desalination of surface, water, process water and effluent. These brackish water systems operate at pressures of 8 – 25 bar (g) and water recoveries of 55 – 99%. Both of which is determined by the feed water composition. Brackish water RO systems are also commonly used in double pass mode to produce ultra pure water for boiler applications.

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Seawater

Seawater desalination is a well-established option for supplying drinking and industrial process water when there is limited availability of good quality surface or groundwater.

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Mine water and ZLD

The treatment of mine waters to recover potable water is a well known and proven technology. The bigger challenge is what to do with the resultant salts that are now concentrated into a smaller brine stream in a cost effective manner. The protection of the environment, space limitations related to the building of new brine ponds and long term legacy risks led the PROXA R&D teams to focus on sustainable brine treatment solutions.

Numerous Zero Liquid brine generation (ZLD) mine water treatment plants have been built by PROXA using a range of different technologies and solutions depending on the composition of the clients feed water, specifically calcium and sodium ions.

In some cases it is possible to achieve ZLD using only membrane processes with the salts being safely exported back into the environment from where they came.

In other cases where high levels of monovalent ions are present (for example sodium), thermal processes are required to treat the highly concentrated brine stream, to recover salt crystals.

Thermal processes include either heating the solution up to boil off and recover the water or freezing to recover the water as ice. In both cases the resultant salt is left behind in a solid form. In addition, PROXA has been a key player in piloting of Eutectic freeze crystallisation for the selective recovery of high purity saleable by-products from brines.

PROXA has used both heating and freezing to produce by-products from mine water effluents.

Our ability to control water chemistry and selectively target specific components in effluent has a significant advantage in ensuring that effluent waters are safe for discharge or alternately can be used to produce drinking water in water scarce areas.

Brine treatment has become an area of concern for the mines due to the high level of salts stored on site, the associated legacy risk and the volumes required for storage. Maximising water recovery from mine waters using membrane processes ensures cost effective solutions.

PROXA has been able to achieve recoveries exceeding 99% using membrane process. The resultant small volume, highly concentrated salt or brine stream can then be treated further to recover the salts in a solid form where required. PROXA has a number of references for brine treatment of sodium and gypsiferous feeds and is the only company running more than five zero liquid brine (ZLD) generation sites at full production in Africa.

Another key advantage from our ability to control water chemistry is to selectively remove high quality saleable products from brine. These products include, amongst others, gypsum used in construction, sodium sulphate used in the detergent manufacture and phosphates used in fertiliser.

PROXA has developed and implemented brine treatment solutions which are cost effective and meet all legislative requirements throughout South Africa, Zambia, Mozambique, Zimbabwe, Tanzania, Ghana, Namibia and Botswana.

Case Studies

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Effluent treatment covers the processes and technologies used to treat wastewater that’s produced as a by-product of industrial or commercial activities. After treatment, the industrial wastewater (or effluent) may be:

  • reused within the process
  • released to a sanitary sewer
  • discharged to a river
  • used as a potable water source for human consumption.

Case studies

Mine water and ZLD

Our ability to control water chemistry and selectively target specific components in effluent has a significant advantage in ensuring that effluent waters are safe for discharge or alterantley can be used to produce drinking water in water scarce areas.

Brine treatment has become an area of concern for the mines due to the high level of salts stored on site, the associated legacy risk and the volumes required for storage. Maximising water recovery from mine waters using membrane processes ensures cost effective solutions.

PROXA has been able to achieve recoveries exceeding 99% using membrane process. The resultant small volume, highly concentrated salt or brine stream can then be treated further to recover the salts in a solid form where required. PROXA has a number of references for brine treatment of sodium and gypsiferous feeds and is the only company running more than five zero liquid brine (ZLD) generation sites at full production in Africa.

Another key advantage from our ability to control water chemistry is to selectively remove high quality saleable products from brine. These products include, amongst others, gypsum used in construction, sodium suphate used in the detergent manufacture and phosphates used in fertiliser.

PROXA has developed and implemented brine treatment solutions which are cost effective and meet all legislative requirements throughout South Africa, Zambia, Mozambique, Zimbabwe, Tanzania, Ghana, Namibia and Botswana.

Case studies

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Sewage

Sewage treatment is the process of removing pollution from household sewage. It includes physical, chemical, and biological processes to remove pollutants and produce environmentally safe treated wastewater.

Normally, the heart of the sewage treatment system is the activated sludge process, which removes organic pollution, and nitrogen and phosphorous compounds, if required.

The activated sludge process may be preceded by grit removal, primary clarification and equalization and superseded by sand filtration, ultra-filtration, maturation, disinfection etc. A by-product of sewage treatment is usually a semi-solid waste or slurry, called waste activated sludge (WAS), that has to undergo further treatment/stabilisation before being suitable for disposal or land application. In most cases, the bulk of the wastewater treated is of household (or municipal) origin, but a fraction can also be of industrial origin.

Sewage treatment systems can vary in size from 2.4 million person equivalent Stickney sewage treatment plant in Illinois to modular “package plants” suitable for treatment of as little as 10 to a few hundred person equivalents. Sewage treatment systems can also vary in complexity ranging from rudimentary reed beds and trickling filters in developing countries to energy efficient moving bed bioreactors (MBBRs) and highly advanced membrane bioreactors that implements ultra-filtration membranes to ensure superior effluent quality. PROXA has in-house design and build capacity to supply both MBBR and MBR turnkey packaged solutions in this field. PROXA has a number of references in this area.

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Landfill leachate

Treatment of landfill leachate is one of PROXA’s key strengths (the treatment of difficult-to-treat industrial water). PROXA has been involved in treatment of landfill leachate water since 2006, which has enabled us to understand the special requirements and unique characteristics of landfill leachate.

Typical characteristics of this liquid include high COD, high Ammonia, high nitrates, high phenol, high hardness and high salt concentrations.

Integration of different processes is required for treatment and can include a combination of processes such as biological nitrification, COD removal, de-nitrification, ultra-filtration, chemical precipitation, ion exchange, membrane desalination and evaporation crystallisation.

Our ability to successfully treat landfill leachate is made possible due to the following capabilities:

  • In-house research and development facility and process laboratory.
  • Pilot plant testing capability.

Case Studies

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Ground water

The remediation of saline or contaminated groundwater for potable or industrial use is often the only reliable water source in arid or remote areas.

The range of applicable treatment processes can vary depending on the nature of the groundwater, e.g. softening for the treatment of hard water, desalination for saline water, remineralisation of corrosive water, or specific processes for the removal of selected contaminants such as nitrate or heavy metals. Hyper-saline groundwater may be treated by thermal processes.

Adequate consideration must be given to the disposal or potential beneficiation of brine and waste streams as the treatment site is typically located inland. The application of a Zero Liquid Discharge (ZLD) scheme may be considered based on the respective economic and environmental drivers.

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Recovery for reuse

The treatment of mine waters to recover potable water is a well known and proven technology. The bigger challenge however, is what to do with the resultant salts that are now concentrated into a smaller brine stream in a cost effective manner.

The protection of the environment, space limitations related to the building of new brine ponds and long term legacy risks led the PROXA R&D teams to focus on sustainable brine treatment solutions.

Over the years, we’ve built numerous Zero Liquid brine generation (ZLD) mine water treatment plants using a range of different technologies and solutions – depending on the composition of the clients feed water, specifically calcium and sodium ions. In some cases, it’s possible to achieve ZLD using only membrane processes with the salts being safely exported back into the environment from where they came. In other cases where high levels of monovalent ions are present (for example sodium), thermal processes are required to treat the highly concentrated brine stream, to recover salt crystals.

Thermal processes include either heating the solution up to boil off and recover the water or freezing it to recover the water as ice. In both cases the resultant salt is left behind in a solid form.

In addition, PROXA has been a key player in piloting of Eutectic freeze crystallisation for the selective recovery of high purity saleable by-products from brines.

PROXA has used both heating and freezing to produce by-products from mine water effluents.

Read more

Side stream filtration

Cooling water forms an integral part of the majority of production processes. The optimisation of the cooling water chemistry is key to mitigating environmental impact by reducing necessary blow-down; preserving life of equipment by reducing the potential for scale formation, and ultimately minimising costs associated to cooling water chemistry control, blow-down storage/management, fresh make-up supply and equipment maintenance/replacement.

Side-stream cooling water treatment, inclusive of both suspended and dissolved solids removal technologies, is a proven method that enables cycles of concentration in the cooling water system to be maximized, while maintaining quality specifications. Implementing side-stream treatment enables cooling water systems to align themselves with the overall target objectives.

PROXA has the necessary expertise to realize these benefits and has successfully assisted their clients in meeting both these objectives in past projects.

Case studies

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Oil separation

Oil/water separation is required by most companies in the mining, power, petrochemical, steel and mineral sectors. Water becomes typically contaminated with oil either through production activities, rotating equipment failure or sporadic oil spills on site.

Oil/water separation becomes necessary when the client’s effluent exceeds the effluent discharge quality specification, or when there is a viable opportunity for water reuse.

This oil, whether it is in free, emulsified or dissolved form, can be separated and then concentrated for disposal, while the treated effluent can either be discharged safely into the receiving environment or alternatively reused in on-site processes.

PROXA has the necessary know-how to successfully employ the latest technology development in oil water separation including the use of chemical demulsifiers, emulsion breakers, oil-skimmers, hydro cyclones, dissolved-air flotation (DAF), API separators and adsorption filtration technology.

Case studies

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Potable

PROXA has a proven track record of treating effluent water, or contaminated water to potable water standards. PROXA has designed and constructed a number of water treatment plants for our industrial clients, where contaminated effluent water is upgraded to potable water, either for re-use on the mine or for drinking water for the community.

PROXA has also constructed a number of plants in which acid mine drainage (AMD) effluent is treated and upgraded to potable water, and in addition to which, generates no liquid waste stream thus being classified as a Zero Liquid Discharge (ZLD) plant.

Furthermore, PROXA is able to treat river, borehole or sea water to a quality suitable for human consumption. The processes used can range from softening, filtration and disinfection to more complex membrane applications.

The use of modular skids is of importance for rural areas, commercial buildings and the military, where simple “plug and play” solutions are required.

In both instances, a number of technologies are employed to achieve the required product water quality.

PROXA also offers a full range of emergency mobile skids for use during periods of drought to water stricken areas.

Case Studies

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Boiler feed water

Thermal power plants generate power through the combustion of a feed source, which superheats water to steam in a boiler. This high-pressure steam is then used to drive the power generation process.

Over time, the generation of steam results in the concentration of impurities within the boiler system. This leads to scaling of the boiler, which in turn results in lower efficiency through heat retardation.

As such, the quality of the feed water to the boilers needs to be of an exceptional quality to lessen the risk of scaling, corrosion and damage to equipment; in addition to limiting the loss of production due to blowdown of the system.

The treatment of the feed water is critical to the operation of the boiler and ensuring high availability of the power plant. A number of treatment technologies can be used to remove the contaminants in the feed water – depending on the nature and quantity of the pollutants and the required water quality in the power generation cycle. External water treatment is preferred so that there’s no corrosion of equipment. These processes include reverse osmosis, deionisation (IX or EDI), softening and evaporation.

PROXA understands the dangers of poor boiler feed water quality and is able to custom design plants based on the process requirements. To date, we’ve designed and built a number of custom plants to suit the needs of the client. These plants produce exceptional quality water and achieve high availabilities, ensuring that the power generation plant remains in service.

 

ansaldo dedisa plant    view of ansaldo dedisa

Case Studies

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Process water

PROXA serves a number of industrial sectors, including: mining, power, petrochemical, steel, mineral, food & beverage and more. In each of these sectors water plays a critical role in the various processes being employed.

However, this process water is often contaminated and needs to be treated prior to discharge, or reuse for alternative applications. PROXA has assisted a number of clients in treating their process water to various qualities for reuse elsewhere on the plant. Process water and/or contaminated effluent can also be treated to qualities suitable for human consumption where water can be distributed to communities.

The treatment required depends on the contaminants present in the process water, and the quality required for either reuse of the process water or for discharge to the environment. In some instances, clients need to treat their potable water further for use as process water where a superior quality is required, such as boiler feed water. PROXA has the experience, skill and technology available to tailor the treatment process to the client requirement on a case-by-case basis.

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Recovery for reuse

The re-use of domestic and industrial effluents by treatment with the various membrane-based processes, ranging from filtration to desalination in different configurations, can be implemented to augment water supplies.

The choice of treatment technology is a function of both the nature of the pollutants in the effluent and the quality, including the type of end-use, of the treated water. A distinction is made between direct or indirect and potable or industrial re-use applications. The best practice in water re-use projects applies the multiple barrier approach to achieve the desired removal and control of pollutants.

To this end, the cost of recovering water for re-use is strongly related to the required water quality and the associated treatment requirements and costs for both supply and discharge. Where water quality requirements are relatively low, or where wastewater discharge costs are high, the re-use of water is likely to be more attractive.

We realise that the direct re-use of treated effluent from domestic wastewater treatment works, rather than indirect re-use for industrial use, has a psychological component. However, we are of the opinion that water should not be judged by its history, but rather by its quality.

References:

  • Radiant – Dubai, UAE
  • AL HILAL – Fujairah, UAE
  • Voltas – Abu Dhabi, UAE
  • IBIS Novotel Hotel – Dubai, UAE
  • Palm Beach Linen – USA
  • West Port Linen – USA

Case Studies

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Bio energy

Bio energy recovery is emerging as one of the leading forms of sustainable energy/electricity generation and has seen a strong positive growth in application over the past decade. Typically, these processes have a significantly reduced CO2 footprint compared to conventional feedstocks such as coal, oil and even natural gas.

Although a number of emerging technologies like microbial fuel cell technology and microbial hydrogen production are currently in the R&D phase, the primary commercially practiced methods are incineration and biogas combustion. Biomass incineration becomes economical if the biosolids concentration is such that it can be combusted. This process might be preceded by a drying step. The heat of combustion is used to generate steam which can be returned to the process, or applied to generate electricity via a steam turbine.

The anaerobic digestion process uses organic pollution in waste water as a source of food and produces a gas mixture of carbon dioxide and methane as waste product. The gas mixture is known as biogas. This biogas is combustible and can therefor be applied to electricity or steam generation. Anaerobic biogas has been applied for steam generation in dedicated and co-fired boilers and also in reciprocating gas engines and turbines for electricity generation.

The monetary value of electricity recovered from biogas generated on the waste water treatment system is so significant that it normally yields a positive payback period between of 4 and 15 years, depending on a number of factors.

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