Abstract
Abstract Within the research project HypoWave, a hydroponic system for plant production was investigated. The hydroponic system was fed with wastewater that had undergone specially adapted treatment. The principal aim was to develop a combined system for water treatment and hydroponic plant production, where water and nutrients were reused efficiently to produce marketable food products. Another goal was to find out whether the reuse of pre-treated wastewater for plant growth in a hydroponic system could also present an additional alternative wastewater treatment step for enhanced nutrient removal. A pilot plant, consisting of various treatment steps such as activated sludge process, ozonation and biological activated carbon filtration, was used to produce lettuce with irrigation water of different qualities. The hydroponic pilot plant was operated in two different modes – flow-through and feed & deplete. This paper focuses on the influence of the various modes of operation and accordingly varying nutrient concentrations (N, P, K) on plant growth. Furthermore, heavy metal content in the various types of treated wastewater and in the produced plants was investigated. In addition, the results of the different modes of operation were verified by mass balances for N, P and K.
Highlights
Agriculture, which consumes 70% of the fresh water resources utilized by mankind, is the greatest water user of all (FAO )
In the existing wastewater treatment plant (WWTP), chemical oxygen demand (COD) could be decreased by 96%
This is contrasted by treatment process C, where due to the operation of the sequencing batch reactor (SBR), the elimination of the COD only amounted to η 1⁄4 89%
Summary
Agriculture, which consumes 70% of the fresh water resources utilized by mankind, is the greatest water user of all (FAO ). Climate change, growing population and urbanization are expected to increase the pressure on water resources and on the availability of arable land and nutrients (WHO a, b; Jiménez & Asano ). This makes it increasingly difficult to guarantee food security and to prevent the deterioration of ecosystems. The investigation of alternative water resources for agricultural irrigation and production is necessary. Even treated wastewater contains problematic substances, such as heavy metals, salts, micropollutants or human pathogens. Treated wastewater could cause salination of the soil and groundwater resulting in losses of plant productivity (WHO b; Marcar et al ; Jaramillo & Restrepo ). Once a critical concentration is reached in the human body, heavy metals become toxic
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