Effect of Bio-Electrochemical Treatment of Hydroponic Effluent on the Nutrient Content

Abstract

This study examined the effect of bio-electrochemical treatment processes on nitrogen and phosphorus removal, but it also evaluated the impact of the treatment processes on the concentration of other nutrients present in hydroponic effluent. A bio-electrochemical reactor (BER) was used in the experiment to treat effluent from the hydroponic cultivation of tomatoes. It was stated that the nitrogen removal efficiency decreased with increasing current density. The study showed that an electric current density of 0.63 A/m2 ensured the lowest effluent nitrate concentration. The nitrogen removal efficiency ranged from 41.6%-R1 (density of 0.63 A/m2) to 8.9%-R4 (density of 5 A/m2). Electric current density higher than 1.25 A/m2 resulted in lower total nitrogen removal efficiency. The total phosphorus removal efficiency increased with increasing electric current density. The phosphorus removal efficiency was the lowest—95.1%—in the R1 reactor, whereas it was the highest in R4—99.1%. The concentration of the other elements in the effluent was determined. The content of molybdenum, boron, sulphates, and potassium did not meet the acceptable norms for discharging hydroponic effluent into the environment. The study showed that bio-electrochemical processes taking place in BER caused secondary contamination of hydroponic wastewater with molybdenum ions.

The Impact of Electric Current for Sewage Sludge Characteristics from Anaerobic Sequencing Bio-Electrochemical Treatment of Sewage Generated During Soilless Tomato Cultivation

“…Trends observed in the changes of the contents of the above elements are consistent with the results of physicochemical analyses of effluent described by Bryszewski et al [2022]. Similar trends in the contents of phosphorus, carbon, calcium and magnesium have also been reported by Bryszewski et al [2021].…”

“…Zinc present in the sewage sludge was most likely removed by electrocoagulation, which resulted in its content decrease by 81% (R3 and R4) to 95% (R1 and R2) from the initial value of 1.65±0.26 mg Zn 2+ /L [Bryszewski et al 2022]. As Chen et al [2018] posited, the removal of zinc during electrocoagulation is likely to be due to: (I) precipitation of hydroxides, (II) adsorption on iron hydroxide flocs, (III) cathode reduction to the metallic form, and (IV) co-precipitation of counter-charged colloidal particles formed during the electrocoagulation process.…”

Evaluation of the Characteristics of Pollutant Discharge in Tomato Hydroponic Wastewater (HWW) for Sustainable Water Management in Korea

“…Heavy metals are also an essential requirement for hydroponics [130,131]. The mean value of Fe was 1.72 ± 1.08 mg/L, that of Mn was 0.33 ± 0.31 mg/L, that of Zn was 0.46 ± 0.32 mg/L, that of Cu was 0.16 ± 0.28 mg/L, that of B was 0.96 ± 0.50 mg/L, and that of Mo was 0.02 ± 0.02 mg/L.…”

Water Nutrient Management in Soilless Plant Cultivation versus Sustainability

“…In turn, in the study conducted by Kwon et al [27], these values oscillated between 48-494 mg N/L and 12.7-106 mg P/L. Apart from nitrogen and phosphorus compounds, other macronutrients and micronutrients contained in the nutrient medium, such as calcium, magnesium, or potassium, are discharged with the drainage water [27,36]. Table 1 presents an overview of the physicochemical indicators of greenhouse effluents.…”