Struvite precipitation for nutrient recovery from wastewater and sewage sludge has been attracting interest, due to the remarkable fertiliser quality of the product. A method to recover struvite from digested sludge was developed at Stuttgart University, involving first an acidic dissolution of nutrients from digested sludge followed by a precipitation step. The application was first tested in a pilot scale plant and recently upscaled to a semi-industrial size by constructing a recovery plant at a municipal wastewater treatment plant. The study reports on the technical features and the operation of the large-scale plant with a short overview on the pathway leading to the construction, as well as quality of the product.
A medium-scale membrane bioreactor was tested in a large tourist resort on the south-western coast of Turkey with the treated wastewater subsequently being used for irrigational purposes. The wastewater treatment system was designed to eliminate carbonaceous and nitrogenous substances. Treatment efficiency was monitored by means of regular chemical and microbiological analyses. Information was collected on water use at different locations of the hotel. Specific values based on the number of guests were determined. Wastewater streams from kitchen, laundry and rooms were analysed to investigate the various contribution from these points. The social acceptance of the guests concerning the on-site wastewater treatment and reuse in the hotel was analysed using a questionnaire. The investigations indicated that the treated wastewater provides the required chemical and hygienic conditions to satisfy requirement for its reuse in irrigation. The acceptance by guests was encouraging for such applications.
The critics against the land use of sewage sludge in Germany lead the research institutions to investigate methods for nutrient recovery. Current research proved that the nutrients such as nitrogen or phosphorus can be recovered. Though, the costs still must be reduced to compete with the conventional production using fresh raw material. Recovery products are not listed in current legislations concerning fertiliser use, therefore the land use of the recovered products require some legislative replenishments.
The paper portrays the current situation concerning the above discussions with an overview on the actual recovery technologies
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