Waterworks residues: dispose or recycle?

Waterworks residues are generated during the treatment of drinking water, especially during flocculation and filtration. Residues include both the accrued slurries and the filtration materials. As a result of changing requirements and statutory regulations (e.g. Waste Management Act, German Soil Protection Act, Fertiliser Ordinance, Act on Fertilisers and Fertilising), water supply companies must increasingly work on finding recycling pathways for their waterworks residues, as the method of waste management used to date is no longer possible. Landfill sites no longer accept every residue and waste management companies demand test reports with details on ingredient concentrations and may refuse to dispose of them. In some cases it may be useful to collect together the same type of residues that occur in the different treatment stages to make it easier to reuse them. In the short-term, this generally requires investment, however it can pay off in the medium to long term. Calcareous residues collected from a single origin can be used, for example, to raise the pH value or for liming, whereas they cannot usually be reused when mixed with flocculant slurries.

In a joint project funded by the German Federal Environmental Foundation (DBU), which was managed by DBI Gas- und Umwelttechnik GmbH, TZW addressed the possibilities of using filtering sand from the iron removal step for hydrogen sulphide in the gas cleaning process. The filter sand can be seen as a starting material for iron-based gas cleaning materials, which is especially attractive to operators of biogas plants. Preliminary measurements by DBI show that used filter sand, provided by water supply companies due to decontamination work, provide comparable or in some cases even better hydrogen sulphide removal rates than the adsorbents available on the market. This therefore opens up a new recycling path for filter sand from iron removal. As the prevailing boundary conditions in individual water supply companies are very different, there are no universal solutions. In fact, each case has to be considered on an individual basis. As an innovative company, TZW advises water supply companies on this topic and develops tailored solutions. It draws on findings from numerous R&D initiatives and projects with multiple water supply companies.

Contact and further information:

Dr. Pia Lipp, Tel.: +49 721 9678-127, E-mail: pia.lipp@tzw.de

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