Small wastewater treatment plants in Flanders (Belgium) : Standard approach and experiences with constructed reed beds

• Published in: Water Science & Technology Vol. 41; no. 1; pp. 57 - 63
• Main Authors: VANDAELE, S, THOEYE, C, VAN EYGEN, B, DE GUELDRE, G
• Format: Conference Proceeding Journal Article
• Language: English
• Published: London IWA 2000; IWA Publishing
• Subjects: Applied sciences; Belgium; Biological and medical sciences; Biological treatment of waters; Biotechnology; Buildings. Public works; Consents; Construction standards; Denitrification; Drainage area; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Limiting factors; Nitrification; Nitrogen removal; Organic phosphorus; Other wastewaters; Pathogens; Phosphorus; Phosphorus removal; Pollutants; Pollution; Reed beds; Reedbeds; Removal; Sewerage works: sewers, sewage treatment plants, outfalls; Sewerage. Sewer construction; Surface flow; Vertical flow; Vertical mixing; Wastewater; Wastewater treatment; Wastewater treatment plants; Wastewaters; Water treatment and pollution; Water treatment plants; Belgium; Europe; Flanders; Domestic waste water; Small dimension; Reed; Artificial medium; Waste water purification; Wetland; Sewage treatment plant; Biological purification
• ISBN: 1900222205; 9781900222204
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2000.0010

In Flanders (Belgium) an estimated 15% of the population will never be connected to a central wastewater treatment plant (WWTP). Small WWTPs can be a valuable option. Aquafin bases the decision to build SWWTPs on a drainage area study. To realise an accelerated construction the process choice is made accordingly to a standard matrix, which represents the different technologies in function of the size and the effluent consents. A pilot scale constructed two-stage reed bed is used to optimise the concept of the reed beds. The concept consists of a primary clarifier, two parallel vertical flow reed beds followed by a sub-surface flow reed bed. The removal efficiency of organic pollutants is high (COD: 89%, BOD: 98%). Phosphorus removal is high at the start-up but diminishes throughout the testing period (from 100% to 71% retention after 7 months). Nitrogen removal amounts to 53% on average. Nitrification is complete in summer. Denitrification appears to be the limiting factor. In autumn leakage of nitrogen is assumed. Removal efficiency of pathogens amounts to almost 99%. Clogging forms a substantial constraint of the vertical flow reed bed. Problems appear to be related with presettlement, feed interval and geotextile.