Treatment of Anaerobic Digester Effluent Using Acorus calamus: Effects on Plant Growth and Tissue Composition.

The responses of Acorus calamus under greenhouse conditions for 56 days when exposed to three dilutions (25%, 50%, and undiluted) of anaerobic digester effluent from a swine farm were determined. Plant growth, morphology, pigments, and minerals in plant tissues as well as water quality were investigated. The plants grew well in all concentrations of anaerobic digester effluent with no statistically significant effects on plant growth and morphology, and without any toxicity symptoms. The NH₄⁺ concentrations in leaves and roots and the NO₃− concentrations in leaves as well as the nitrogen, phosphorus, and potassium concentrations in the plant tissues increased with increasing effluent concentration. The nutrients in the anaerobic digester effluent were removed effectively (NH₄-N > 99% removal; PO₄-P > 80% removal), with highest removal rates in the undiluted digester effluent. The removal of total suspended solids (>80% in 42 days) and chemical oxygen demand (37⁻53%) were lower. The dissolved oxygen concentration in the anaerobic digester effluent increased overtime, probably because of root oxygen release. It is concluded that Acorus calamus could be a promising species for treating high-strength wastewater with high nutrient concentrations, such as effluents from anaerobic digesters as well as other types of agricultural wastewaters.