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Posted on 20 December 2017 by Hubert Colas
Posted in Utility management, Wastewater Management, Water and wastewater community, Tagged Quebec, sludge, solar,

Sludge management, a complex challenge

Sludge management originating from wastewater treatment plants has always been a highly complex, costly activity and quite dangerous. If poorly executed, the environmental and sanitary advantages may be jeopardized. (von Sperling, M and Andreoli, C.V., 2007, in Sludge Treatment and Disposal, IWA publishing, London UK.) A new approach using concentrated solar technology may prove a viable and cost-effective alternative to traditional technology.

Cutting-edge techniques to improve sludge management: concentrated solar sludge drier

A pilot system has been implemented for the municipality of Surprise Arizona in the summer of 2017. The system consists of two parabolic trough solar concentrators of 33.58 m in length (110 ft) and 2.34 m in width (7.7 ft). Water is heated by the sun in an absorber tube to 121 °C at 5 bars. It is then pumped to a storage tank via underground pipes. The stored heat can then be used for day and night operations. The heated water the circulates through pipes in drying beds filled with sludge. The two rows of collectors, with a total surface area of 150 m2, generates heat at an effective power of 98 kW.

This simple solar and piping system dries the sludge from the wastewater treatment plant sludge down to a staggering 90-97% solids content. This system can process 2 Tons of sludge per day. The resulting dried, sterile, granular biosolid can then be safely used as a fertilizer supplement, soil conditioner, or green fuel. It Is rated as a Class A sludge that complies with EPA Part 503 Biosolids Rule. The volume of the resulting dry product saves enormously on the cost of transportation of the sludge disposal.

Implemented by Heat2Hydro Inc, a New York based company and the solar troughs are manufactured by Rackam Inc. (Sherbrooke, QC), the pilot plant outcomes demonstrate that this approach is very efficient. The municipality of Surprise AZ is now planning to expand the facility to process up to  100 Tons of sludge per day by 2020, which would increase its capacity of 5 MW at full scale. The turnkey project is expected to cost 1,000 USD/kW or 10 USD/kg/d capacity.

Compared to other traditional methods of sludge treatment and disposal, such as land application as fertilizer, disposing of it in landfills, drying and/or incineration, the solar alternative seems a very viable alternative.

Although a few regions may benefit from the sun and heat available in Arizona, a new project is to be implemented, using the same technology in Quebec, Canada, in the summer of 2018. The initial studies also proved cost-effective even in such a northern climate.



About the author

Hubert Colas, Eng., Ph.D., is a senior executive at FluksAqua with more than 25 years of experience in consulting engineering and technology development.
In previous functions, Mr. Colas spearheaded a world-class leader in the design and operation of real time control of urban drainage systems. Hubert Colas implemented complex solutions to manage wet weather in real time and provided services and solutions to water and wastewater utilities.