WET News

Odour control criteria is shifting. Is the long-term cost of equipment as important as the initial investment? The challenge: Lowest investments can lead to higher costs INSIGHT ODOUR CONTROL The PLC allows very easy control and data acquisition via internet / plant SCADA, and also automatic control and optimisation of the water usage T echnologies for odour control, including biolog- ical, have been widely re- viewed and their optimal range of application and perfor- mance has been clearly estab- lished. From a process perspective it is proven that the performance and reliability of biotricking fil- ters with synthetic media are equally as good, if not better than lava filters, chemical scrub- bers, activated carbon, thermal oxidisers and other conven- tional technologies. However, looking at the process economics more and more organisations realise that odour treatment technologies with the lowest investments present the highest operating costs. This means that the Net Pre- sent Value (NPV) will increas- ingly become a selection crite- ria rather than investment costs. Biotrickling filters with synthetic media are also the most cost-effective and likely technology to be considered first for odour treatment at WwTP's considering NPV. With this change just beginning in the UK, Pure Air Solutions has already installed four Sulphus systems in the UK in the past year – one at an industrial plant and three at sewage treatment works. Activated carbon One of the systems is installed at one of the largest sewage treatment works in the North- east, treating wastewater from a population equivalent to more than 800,000 people including wastewater from industrial sites. At this sewage treatment works the Odour Control Sys- tem comprises a Sulphus biotrickling filter system fol- lowed by an activated carbon adsorber as a polishing unit, to get even below 0.1ppm H2S at the stack outlet. Since the activated carbon unit would only need to handle peaks of less biodegradable compounds, the Sulphus sub- stantially increases the life time of the activated carbon. More recently at a sewage treatment works south of Lon- don, an existing chemical scrubber was converted into a Sulphus as a feasible and cost- saving alternative to control H2S and odorous air emissions. Like in a lot of other cases and scientific research biotrickling filtration proves to be a feasible and cost-saving alternative to control H2S and odorous air emissions. The low operational costs of a Sulphus in comparison with chemical scrubbers is mainly due to its lower energy con- sumption, very low mainte- nance and the fact that biotrickling filters require no chemicals. That is why an increasing number of full scale wet chemi- cal scrubbers are successfully being converted into biotrick- ling filters when using an inert synthetic packing of 600m 2 /m 3 of specific surface area like the Sulphus, while with 125m 2 /m 3 performance is very poor. n "The low operational costs of a Sulphus in comparison with chemical scrubbers is mainly due to its lower energy consumption, very low maintenance and the fact that biotrickling filters require no chemicals." THE CONCEPT • Sulphus can treat H2S and other (in)organic odours in one single reactor • The OdourPack winded plastic packing media inside the vessel serves as the support material for the development of the biofilm • Operationally, the oxygen and pollutants mass transfer from the gas phase to the biofilm where the biodegradation takes place. The high specific surface area of the OdourPack enhances this mass transfer • All of the OdourPack's surface is available for biomass growth, and there are no internal pores that can get clogged • The OdourPack can be easily removed and installed again in the bioreactor vessel NEED TO KNOW Odour treatment technologies with the lowest investments present the highest operating costs An increasing number of full scale wet chemical scrubbers are successfully being converted into biotrickling filters The low operational costs of a Sulphus in comparison with chemical scrubbers is mainly due to its lower energy consumption THE VERDICT At the sewage treatment works in the North-east, using the Sulphus instead of a chemical scrubber the savings in chemicals amounted to more than £207,000 a year, and there are savings in energy consumption as well as in the maintenance work. • SHARE YOUR OPINION... yoursaywn@fav-house.com SEPTEMBER 2014 WET NEWS 21

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