Towards a water-wise world Annual report 2014

Tessa van den Brand doctorate 

Incorporating the sulphur cycle in sewage water treatment results in less sludge

15 October 2014Research

KWR researcher Tessa van den Brand receives her doctorate from TU Delft for her research into the sulphate-reduction process (a component of the SANI process) at low temperatures in the treatment of household wastewater. The SANI process was developed by the Hong Kong University of Science and Technology and TU Delft. The process relates to the treatment of wastewater with high sulphate concentrations, which can be treated biologically, that is, by sulphate-reducing bacteria (SRB). Van den Brand studied the operation of the process in a mild (Dutch) climate.

Sulphate-reducing bacteria (SRB) play an important role in the SANI process (SANI: Sulphate reduction, Autotrophic denitrification and Nitrification Integrated). Despite the fact that SRB are often seen as undesirable because of the associated odour nuisance and corrosion formation, this form of biological wastewater treatment, under well-controlled operational management, involves significant advantages. The application of SRB results in good removal levels of organic material and lower levels of sludge production, and makes a compact treatment system possible. Additionally, SRB can be used for the removal of heavy metals and pathogens.

Lab research

A crucial condition for the successful application of SRB is the presence of sufficient concentrations of sulphate. In a few cases, the influent in wastewater treatment plants (WWTPs) in the Netherlands contains sufficient sulphate because the plants are situated close to the coast. A high sulphate concentration can also be achieved through seawater toilet flushing or the admixture of industrial wastewater. The laboratory research conducted by Van den Brand for her doctoral work showed that the relatively low temperatures of 10 and 20° C that are typically prevalent in Dutch WWTPs, do not constitute an impediment to the application of SRB. Moreover, the regular fluctuations in nitrogen, phosphorous, salts, sulphate, sulphide and organic materials have no effect on SRB application, even when they are ten times their expected concentrations in the influent. The fact that household wastewater naturally contains propionate, which renders the SRB active, contributes positively to the results.

Continuation: pilot-research

In September 2014, KWR, Paques and Delfluent Services started a pilot research project within TKI Water Technology. The research is being carried out in a test facility at WWTP Harnaschpolder, so that the SRB are being fed with real, as opposed to artificial, wastewater from the WWTP.

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Scientific publications
Influence of acetate and propionate on sulphate-reducing bacteria activity.

Temperature effect on acetate and propionate consumption by sulphate reducing bacteria in saline wastewater