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.


  • Regarding the processes of wastewater treatment as a very specific production of high-quality irrigation water, which is reused in a hydroponic system for growing lettuce.

  • Investigation of the effects of various treatment processes (activated sludge process, expanded granular sludge bed reactor, ozonation, biological activated carbon filtration) on the quality and suitability of the produced waters for hydroponic lettuce production.

  • Comparison of different modes of operation of the hydroponic system (flow-through and modified circulation system (feed & deplete)).

  • Evaluation of nutrient and heavy metal content of the hydroponically cultivated lettuce.

  • Verification of the achieved results in regard to the nutrient elimination and nutrient content of the lettuce by mass balances (N, P, K).

Graphical Abstract

Graphical Abstract
Graphical Abstract
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