Wastewater-fed Aquaculture, Otelfingen, Switzerland: Influence of System Design and Operation Parameters on the Efficiency of Nutrient Incorporation into Plant Biomass

Abstract

A wastewater-fed, partly indoor aquaculture plant consisting of 36 basins with a total area of 360 m, charged with effluent from a methanization plant processing organic household waste (Kompogas System), started operation in spring 1998 in Otelfingen, Switzerland. Due to high effluent concentrations on one hand (total organic carbon, total nitrogen, and total phosphorus concentrations being 670, 255, and 52 mg l, respectively) and stringent wastewater regulations on the other hand, the aquaculture was split into modules and stocked with organisms of different environmental requirements. The modular structure, as opposed to traditional one-pond polyculture, allowed manipulation and better nutrient budgeting of the system. Research focused on nutrient-recycling efficiency of a wide array of modules, producing biomass such as algae, fish, zooplankton, and aquatic macrophytes as ornamental plants (Eichhornia, Pistia, Ipomoea, Lemna, Azolla) which were suitable for sale on the Swiss market. Different arrangements of modules, of water and wastewater flows and of nutrient concentrations were tested in 3 years, 1998–2000. Our research showed that aquaculture can be set up to either produce treated wastewater ready for discharge into surface waters or to maximize nutrient recycling through biomass production. In the first case, the recommended loadings are below 0.47 g N m day and 0.084 g P m day, in the latter 4.3 g N m day and 0.31 g P m day still resulted in a 78% removal of nitrogen and 28% removal of phosphorus. Through weekly biomass harvest, up to 0.36 g N m day and 0.06 g P m day were converted into plants. With appropriate planning and plant selection and management, it was possible to increase the fraction of nutrients eliminated via primary production up to 40%, which is significantly higher than reported in the literature. 1 University of Applied Sciences Waedenswil, Institute of Natural Resource Sciences, Section Ecological Engineering, Gruental, CH 8820 Waedenswil, Switzerland (*u ) Corresponding author: e-mail: jura@zhaw.ch J. Vymazal (ed.) Wastewater Treatment, Plant Dynamics and Management 299 in Constructed and Natural Wetlands, © Springer Science + Business Media B.V. 2008 300 A. Graber, R. Junge-Berberovic