Hydroponic system for the treatment of anaerobic liquid

Abstract

The effluent from anaerobic digestion process has high concentrations of nutrients, particularly nitrogen essential for plant growth but is not suitable for direct disposal or application due to high chemical oxygen demand (COD), low dissolved oxygen (DO), odour issues and potentially phytotoxic.This research explored the optimum conditions of anaerobic effluent for application and dilutions of the effluent required to obtain better plant growth. A small-scale hydroponic system was constructed in glasshouse to test different concentrations of anaerobic effluent against a commercial hydroponic medium as the control for the growth of silverbeet. It was found that the survival of silverbeet was negatively affected at 50% concentration due to low DO and NH 4 -toxicity. The concentration of 20% anaerobic liquid was found to be the most efficient with highest foliage yield and plant growth. The hydroponic system with 20% concentrated effluent had better utilisation of nutrients for plant growth and a COD reduction of 95% was achieved during the 50 days growth period. This preliminary evaluation revealed that the growth and development of silverbeet was significantly lower in anaerobic effluent compared to a commercial hydroponic plant growth solution.The nutrient quality of anaerobic effluent could be highly variable with the process and the waste material used and dilution may depend on the nutrient content of the effluent. It is recommended that, a pre-treatment of the effluent to increase DO and reduce ammonium content is required before plant application and simple dilution by itself is not suitable for optimum plant growth in a hydroponic system.

The Effect of Anaerobic and Aerobic Fish Sludge Supernatant on Hydroponic Lettuce

“…Although some research was carried out on the impact of domestic sewage and industrial wastes on plant growth [9][10][11], to date, the impact of aerobically and anaerobically treated RAS-derived sludge on plant growth has not yet been experimentally investigated. Effluents from anaerobic digestion generally have high concentrations of nutrients, as sources of carbon are metabolized preferentially during treatment [9,11].…”

“…Effluents from anaerobic digestion generally have high concentrations of nutrients, as sources of carbon are metabolized preferentially during treatment [9,11]. However, most anaerobic effluents are characterized by high chemical oxygen demands (CODs), hydrogen sulfides (H 2 S) content, and low dissolved oxygen (DO) concentrations, and thus can be considered phytotoxic.…”

Opportunities and Challenges of Multi-Loop Aquaponic Systems

“…However, just like the temporary H2S availability in system ANA, the observed SO4 concentration is much lower than recommended for hydroponic practice (Resh, 2012;Sonneveld and Voogt, 2009c). Another factor that decreases plant growth is a high COD level (Krishnasamy et al, 2012), which is much higher in anaerobic effluents than in aerobic effluents. Since our systems were highly aerated and showed a saturated DO level over the entire experimental period, we can reject this assumption.…”

“…Although some research was carried out on the impact of domestic sewage and industrial wastes on plant growth (Krishnasamy et al, 2012;Penetra et al, 1999;Salminen et al, 2001), to date, the impact of aerobically and anaerobically treated RAS-derived sludge on plant growth has not yet been experimentally investigated. Effluents from anaerobic digestion generally have high concentrations of nutrients, as sources of carbon are metabolized preferentially during treatment (Krishnasamy et al, 2012;Salminen et al, 2001).…”

“…Effluents from anaerobic digestion generally have high concentrations of nutrients, as sources of carbon are metabolized preferentially during treatment (Krishnasamy et al, 2012;Salminen et al, 2001). However, most anaerobic effluents are characterized by high chemical oxygen demands (COD), hydrogen sulphides (H2S) content, and low dissolved oxygen (DO) concentrations, and thus can be considered phytotoxic.…”