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    The Effect of Retention Time and Seasonal Variation on the Characterization of Phyto-Remediated Aquaculture Wastewater in a Constructed Wetland
    (2025-10-01)
    Akadiri, Shadrach A.
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    Dada, Pius O.O.
    ;
    Badejo, Adekunle A.
    ;
    Adeosun, Olayemi J.
    ;
    Ogunrinde, Akinwale T.
    The insufficient availability of safe water has emerged as a prevalent issue severely impacting public health in developing nations. Moreover, studies reporting the efficacy of treatment plants (TPs)—specifically Phragmites karka and Typha latifolia—in removing toxic elements in aquaculture wastewater are scanty. Therefore, this study is aimed at investigating the effects of hydraulic retention time (HRT), seasonal variations, and TPs on the removal efficiency of pollutants from a vertical subsurface flow constructed wetland (VSSF-CW) in Nigeria. The experiments spanned three seasons (November–December–January—NDJ; March–April–May—MAM; and July–August–September—JAS) of the year, with samples collected from the CW at 7 day intervals for analysis. The aquaculture wastewater was analyzed in the laboratory to determine its chemical and toxic compositions before and after the introduction of treatment plants. Three-way ANOVA was used to analyze the main and interactive effects between HRT, seasons, and TPs on the physicochemical properties of the CW’s effluents. The removal efficiency was determined to evaluate the performance of the constructed wetland in comparison to the treatment plants. Results showed that these constructed wetlands effectively removed contaminants, with significant differences (p < 0.05) mostly observed in the effects of treatment plant types and seasons on the chemical and heavy metal concentrations. This was further confirmed by the main effects of HRT, seasons, and treatment plant choice, which significantly (p < 0.05) influenced treatment efficiency. Removal efficiencies increased with longer HRTs, reaching peak removal efficiencies of approximately 69, 67, and 61% for Na, K, and Ca, respectively. The BOD and COD reached 85 and 90% removal efficiency, while removal efficiency of 100% was achieved for most heavy metals at 21 day retention time. In summary, the study found that TPs (Phragmites karka and Typha latifolia), HRT, and seasonal variation are important for treating integrated poultry and aquaculture wastewater in a VSSF CWs.
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    Immobilisation of soil cadmium and lead by an integrated approach of SICP and absorbent additives
    (2025-09-30)
    Wang, Yuchen
    ;
    Li, Mingdong
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    Zhang, Shiai
    ;
    Ni, Junjun
    ;
    Kamchoom, Viroon
    The combined effects of various soil additives and soybean urease-induced carbonate precipitation (SICP) on soil heavy metal immobilisation remain poorly understood. This study aims to immobilise the soil cadmium (Cd) and lead (Pb) using the SICP technique in combination with various additives, as well as to determine their optimal application dosages. Three additional additives (i.e. porous silicon, coconut shell biochar, and sorbitol) were examined. Among the three additives, coconut shell biochar combined with SICP showed the most significant improvement in the immobilisation of soil cadmium. With an optimal mixing ratio of 10% (by mass), the content of cadmium in the exchangeable state was reduced by 41% compared with the SICP-only group, and the Cd leaching concentration decreased by 45%. In the case of lead-contaminated soils, sorbitol combined with SICP yielded the most significant enhancement. An optimal dosing of 1% (by mass) reduced the lead content in the exchangeable state by 66% and the leaching concentration by 45% compared with the SICP-only group. This was attributed to the ability of sorbitol as a nucleating agent to provide additional carbonate binding sites for the formation of carbonate precipitates with lead ions. This study provides valuable experimental data and guidance for heavy metal immobilisation in contaminated sites.