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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.

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Constructed wetlands are an eco-friendly technology used for decades for treating various types of wastewater. To gain new insight into plant selection for wastewater treatment systems in tropical areas, this research investigated growth and ecophysiological responses of Typha angustifolia to different concentrations of anaerobic digester effluent from a swine farm and assessed their influence on wastewater treatment effectiveness. Twelve plants (n = 4 per treatment) were separately grown in 3 concentrations of wastewater (25% and 50% diluted wastewater and undiluted wastewater). All plants grew well in all concentrations. However, the plants tended to have reduced root biomass, root length and decreased pigment contents when exposed to high concentrations. High removal efficiency for electrical conductivity, total dissolve solids, total suspended solids, biochemical oxygen demand, chemical oxygen demand, ammonium nitrogen and orthophosphate was found (73%, 70%, 93%, 99%, 82%, 99% and 80%, respectively, from undiluted wastewater). The dissolved oxygen concentration in the anaerobic digester effluent increased over time because of released root oxygen. The study showed that T. angustifolia developed aerenchyma in its root cortex even under stress conditions. This ability makes this plant tolerant to high strength wastewater. Furthermore, oxygen released from its roots also supports growth of microorganisms and enhances microbial biodegradation processes leading to highly efficient treatment systems.