Photocatalysis and flocculation processes for recycling aquaculture effluent into nutrient-rich irrigation water

This research aimed to create a novel technique for recovering fertilizers from aquaculture effluent to overcome potential non-renewable fertilizers shortages. There are two steps: Photocatalyst technique for nutrient mobilization, succeeded by solids precipitating with two natural and one synthetic flocculant. The photocatalytic degradation of organonitrogen compounds in batch experiments started under the irradiation of sunlight. Following that, photocatalytic breakdown of organonitrogen compounds produces inorganic nitrogen constituents like NH4+, NO2−, and NO3−, which could be used as manure. It was found that, after 12 h of circulating, the concentration of inorganic nitrogen become as NH4+ = 17.2 g/L, NO2− = 18.1 mg/L, and NO3− = 15.9 mg/L. The jar test was adopted to assess the capacity of two natural compounds (tamarind kernel polysaccharide (TKP) and tannin-based product (TBS)) and synthetic water-soluble polymer cationic polyacrylamide (SWP) to reduce turbidity, total suspended solids (TSS), COD and colour. The findings reveal that with a dose of 20 mg/L of TBS, 20 mg/L of TKP, and 50 mg/L of SWP, the maximum turbidity reductions were 95, 93, and 94%, respectively. The TBS was slightly better than TKP and highly better than SWP in terms of coagulation activities with TSS, COD and colour maximum removal efficiencies.

EFFECTIVENESS OF EICHHORNIA CRASSIPES IN THE TREATMENT OF AQUACULTURE EFFLUENT FROM A FISH FARM IN BENIN CITY, NIGERIA

Aquaculture production has seen much increase in Nigeria in recent times due to the rise in fish farming occasioned by the availability of water and materials for setting up, the profit turn-over, increase in demand for fish, and the effort to curb the rising youth unemployment rate. However, this massive surge of interest in aquaculture and fish farming is accompanied by the challenge of pollution as the effluent from aquacultural settings gets discharged into nearby water bodies hence the need for remediation. Aquatic plants have been used to remediate polluted water bodies and possess many advantages over other methods. Therefore, this study aimed to investigate the effectiveness of Eichhornia crassipes in the clean-up of aquaculture effluent. Wastewater collected from a commercial fish pond in Benin City, Nigeria, were divided into two treatment groups. One group was diluted with an equal volume of distilled water (50%), and the other group consisted of 100% wastewater. Distilled water was used as a control (0%). The samples were treated with Eichhornia crassipes for 14 days, following which samples were collected for physicochemical analysis. The result showed that E. crassipes reduced significantly the pH from 7.44 to 5.98 and 7.28 to 6.10 in the 50% and 100% effluent samples, respectively. The removal efficiency of E. crassipes in the 100% effluent sample was 69% for phosphate, and 94% for nitrate. The study suggests that E. crassipes may be effective in improving the quality of aquaculture wastewater.

Performance of Greenhouse-Grown Beit Alpha Cucumber in Pine Bark and Perlite Substrates Fertigated with Biofloc Aquaculture Effluent

Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for use in AE. This study was conducted from January to July in 2016 and September to October in 2019 to evaluate greenhouse-grown Beit Alpha cucumber (Cucumis sativus L. ’Socrates’) performance fertigated with AE in pine bark or perlite substrates, grown either as one plant or two plants per pot. A 2 × 2 factorial arrangement in a randomized complete block design with four replications for each season was used. The substrate effect on yield in 2016 depended on the density and season. The pooled yield over seasons in 2016 showed pine bark had a significantly higher yield than perlite by 11% in one plant per pot but lowered by the same amount in two plants per pot. In 2019, pine bark significantly reduced the leachate pH in both plant densities and reduced the leachate EC by about 15% in two plants per pot. The foliar boron was occasionally below sufficiency whilst manganese was above sufficiency in pine bark due to its inherently low pH. We conclude that the effect of the substrates on cucumber yield fertigated with AE is dependent on the season and the number of plants per pot. Therefore, due to the local availability of pine bark, it could be a potential substitute for perlite especially when using one plant per pot for AE. In addition, pine bark could be used as an intermediate substrate to reduce the pH in AE for downstream use.