The Hadwaco system for treatment of industrial and municipal waste water, leachate from landfills and for preparing drinking and process water has in a relatively short time become an attractive alternative to conventional evaporation solutions.  Based on mechanical vapour recompression (MVR) and the falling film principle, the system is reported to have several benefits when compared with competing technologies. The advantages include, for example, good purification results, lower energy consumption and lower investments costs. 

Evaporation is generally considered the ideal method for industrial and municipal waste water treatment. However, high investment and operational costs make it an expensive solution. With the new system, the costs of evaporation and the consumption of energy can be lowered by using new materials and better evaporator design.
In the Hadwaco process, the effluent stream is concentrated by vaporising its water content. Dry substances remain in the concentrate and the clean water can be used for processes or simply discharged into the environment.
Thanks to a low operating pressure, the water boils at 50-60 °C. This means that polymeric materials can be used for the heat transfer surface. In principle, the evaporator operates like a heat pump, i.e. the vapour pressure and temperature are increased by fans. The vapour is then reused as heat releasing medium in the same unit for further evaporation of the effluent.
The heart of the new system is the polymeric heat transfer surface, on which the water boils. By using such material, large heat transfer areas can be constructed at significantly lower cost, when compared with metallic surfaces of the same size. With the Hadwaco evaporator, a large heat transfer surface results in low energy consumption, i.e. 8-12 kWh/m3 .
Hadwaco technology is being developed through extensive testing in Europe. Over the last few years, projects with a 12 m3/d pilot unit have been carried out in various applications. Currently, test runs on landfill leachate are underway in Sweden, Italy, Spain and the USA, and on pulp and paper effluents in Norway.
The technology is also being demonstrated in a full-scale model, which, with the help of funding from the European Commission's Innovation Programme, will run for two to three years at Stora Paper Board's Pulp Mill with ECF (elemental chlorine free) bleaching at Gruvön, Sweden.

Recent deliveries
Recently, the company has delivered complete evaporation plants, for example, to a waste managing company in Lahti, Finland, and to a paper mill in Damman, Saudi Arabia. An order from a steel manufacturer in South Africaand has just been secured.
At the Lahti plant, the evaporator is used for the treatment of leachate from a landfill. The feed to the evaporation system is 140 m3 daily. After purification, 130 m3 of clean water, the condensate, is released into the environment. The concentrate, amounting to 10 m3 a day, is returned to the landfill body. The plant is designed to handle about 44,000 m3 of leachate yearly at operating costs of some USD 2 per m3.
In 1996, the Arab Paper Manufacturing Company became the first pulp and paper enterprise to invest in a full-scale evaporation for both effluent treatment and water purification. The evaporation plant, comprising two prefabricated evaporation units complete with instrumentation and control systems, is used at the company's production facility in Damman. One line takes care of the effluent from the paper mill, while the other is used for the purification of salty ground water from a well. The total feed flow to the system is 1,242 t/day of which 1,200 t/day is returned to the paper manufacturing process after purification.
The latest order was received from the South African steel manufacturer Saldanha Steel Pty, which is building a new steel mill in an environmentally sensitive area near Johannesburg. Because of strict regulations concerning the water supply, storm water and sewage effluent must be recovered. The water is carried in a closed system with make-up water as required.
Hadwaco has also made an agreement with the Finnish company Aquamax Oy for the delivery of two evaporator units. The units will be used for producing drinking water from sea water. The final destinations for the units, which will be delivered in September this year, are Egypt and Singapore.


For further information, please contact:
Hadwaco Ltd Oy
Mr. Peter Koistinen
Hämeentie 135, FIN-00560 HELSINKI
Tel. +358 204 3911, fax. +358 204 39 5655

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Technical details on the evaporation plant at the Lahti landfill

Technical data for the plant:
Leachate handling capacity: 44,000 m3/a
Leachate feed: 140 m3/d
Purified water: 130 m3/d
Concentrate to be returned: 10 m3/d
Energy consumption: 12 kWh/m3
Operating pressure: 0.12 bar
Operating temperature: 55 °C

Properties of the purified water:
Ammonium concentration: < 1 mg NH4-N/l
CODCr: < 30 mg O2/l
Conductivity: < 3 mS/m

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