Treatment Techniques for Combined Sewer Overflows

Treatment Techniques for Combined Sewer Overflows

Scherrenberg, S.M.

Van der Graaf, J.H.J.M. (mentor)
Van Loosdrecht, M.C.M. (mentor)
Flamink, C.M.L. (mentor)
De Koning, J. (mentor)
Van Ec, L.C.J. (mentor)

Civil Engineering and Geosciences

Watermanagement

Sanitary Engineering

2006-08-01

During storm events, the flow in a combined sewer system can exceed the capacity and, as a result, a combined sewer overflow (CSO) will occur. During a CSO raw wastewater is discharged to surface water. This wastewater is a mixture of raw sanitary wastewater, raw industrial wastewater and rainwater. The receiving water will get polluted by dissolved as well as undissolved pollutants. Therefore a CSO can cause damage to the ecological and biological state of the receiving water and besides it can cause public health risks. Until now the problem, with respect to CSOs in the Netherlands, is dominated by a quantitative approach. CSO flow rates and frequencies were in the past decades the main subject of research. These frequencies were translated into the Wet Verontreiniging Oppervlaktewater (1970). In the year 1998 the Ministry of Transport and Water Management came with a renewed policy, the fourth Memorandum on Water Management, dealing with groundwater, dehydration and water quality, for the protection and the recovery of nature. At the end of 2000 the European Water Framework Directive (WFD) came into force, which charges the European members of the EU to report obligatory. The aim of the WFD is to have an ecological and biological balance for all surface waters and groundwater in Europe effectively working in 2015. Measures are required to push back the pollution by defined dangerous substances. Measures with regard to the reduction of CSO frequencies alone is not enough to fulfil the legislation. When a CSO occurs an amount of pollutants will enter the surface water. CSO water needs to be treated to prevent pollution and odour annoyances to the surroundings. The goal of this research is to find a suitable treatment technique or a combination of treatment techniques. Primary and secondary techniques, adsorption and disinfection techniques are described. Primary techniques remove suspended solids and a fraction of the organic material, secondary techniques remove suspended solids and biological degradable material. Adsorption techniques are used to remove for example endocrine disrupting substances and disinfection techniques are used to minimize health risks for the population. In the Netherlands CSOs occur five to ten times a year per location. Therefore a treatment technique needs to be able to start up in a few minutes even after a long period without feedwater and should be able to handle wide and quick variations in flow without causing any inconveniences to the surroundings. Primary techniques like sieving, the Netting TrashTrapTM system and sedimentation basins and secondary techniques like membrane filtration, sand filtration and synthetic medium filtration are described. Adsoprtion techniques like activated carbon filtration and ion exchange and disinfection techniques like ozone dosage, chlorine dosage and UV treatment are described.

sewer
overflows
CSO
combined

http://resolver.tudelft.nl/uuid:60337081-7008-4493-bf4c-89851bedd0e4

Student theses

master thesis

(c) 2006 Scherrenberg, S.M.