Investigations into Scum Formation and Management

Investigation into the Scum Formation in Pump Stations in eThekwini

2015 to 2017

Project description

Scum is generally observed as a thick murky layer on wastewater and is commonly comprised of discarded fat, oil and grease (FOG) along with many cleaning chemicals used on a daily basis. Scum management is an important aspect of wastewater treatment. If scum is not removed at the correct rate from the pump stations or wastewater treatment plants (WWTP) during the screening process, the WWTP will not function properly, resulting in odours and effluent quality standards not being met.

To successfully treat and process the scum, the operator of a WWTP needs a clear understanding of the composition of scum, how it is produced, and how it should be managed. In general, scum is heterogeneous and, depending on how it was formed, varies in colour from black to grey or pale brown. Scum is frequently observed in anaerobic reactors of WWTP and accumulates in sewer lines.

The objective of this research project is to (i) obtain a comprehensive knowledge on the composition and biodegradability of scum, and (ii) quantify scum build up in the settler of a decentralized wastewater treatment system (DEWATS), in a tank in a sewage pump station and in the clarifier of a WWTP in Durban (South Africa) that are susceptible to blocked screens. Estimating the scum effect is complicated due to the difficulty in undertaking scum analysis but it is important to undertake research on ways in which pump-stations, screens and other installations can be protected from scum coagulation and hardening.

The outputs from this research will assist eThekwini Municipality in improving the operation of pump stations in the city of Durban.

The Aims of the study are to:

  • Quantify the amount and composition of material removed during Screening of water borne sewage.
  • Quantify Scum build up in the suction well of the wastewater pump stations.
  • Determine the composition and biodegradability of Scum and Screenings.
  • Investigate external factors affecting rate of scum formation.
  • Identify suitable disposal and management on the landfill site.
  • Investigate the reuse of the scum as bio charcoal.
  • Identify the role of scum in leachate treatment and biogas generation. 
  • Srivastava S, Buckley C and Trois C.  An analysis of scum of the pump stations in Durban. Presented at Young Water Professionals, Pretoria, 16 to 18th November 2016
  • Srivastava S, Buckley C and Trois C. Investigations into Scum Formation and Management. Presented at WISA Conference, Durban, 15th – 17th May 2016:


Relevant Publications and Reports

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