Response surface optimization of chemical coagulation for solid-liquid separation of dairy manure slurry through Box-Behnken design with desirability function

Insights to enhanced coagulation based on the control of metal forms for treating acid mine drainage: Performance and mechanisms

This study presents an enhanced oxidation-chelation-coagulation process for efficient acid mine drainage (AMD) treatment, addressing the limitations of conventional methods in terms of efficiency, cost, and environmental risks. Through systematic optimization, it was demonstrated that combined NaClO/KMnO₄ oxidation (3:1 molar ratio) at pH 8 effectively transformed Fe2 +/Mn2+ ions into insoluble Fe/Mn (hydr)oxides, while 0.40 g/L carboxymethyl cellulose (CMC) enabled effective chelation and removal of Pb/Ni. The process achieved exceptional removal efficiencies, reducing Fe from 2000 to 2.85 mg/L while maintaining Mn, Pb, and Ni below or close to China's discharge limits (2.0, 0.5, and 0.5 mg/L respectively). Surface characterization (XRD, XPS, FTIR) results revealed the flocs' composition (Fe(OH)₃/MnO₂) and identified functional groups (-COOH/-OH) onto CMC as crucial for metal chelation. Notably, 36.7-57.7 % of removed metals were stabilized in environmentally inert residual forms within the sludge, minimizing leaching potential. The synergistic combination of oxidation, chelation and coagulation mechanisms provides distinct advantages over conventional approaches, including: (1) superior simultaneous removal of multiple metals (Fe, Mn, Pb, Ni); (2) reduced chemical consumption through optimized reagent combinations; and (3) effective mitigation of secondary pollution risks via metal stabilization. These results provide a robust technical foundation for sustainable AMD remediation, offering significant improvements in treatment performance, cost-effectiveness, and environmental safety. The findings highlight the potential of hybrid chemical processes for complex wastewater treatment and provide valuable insights for practical implementation in mining-affected regions.

Green coagulation and flocculation: Scenedesmus algal extract-loaded chitosan/poly(vinyl alcohol) cryogel for effective water treatment

This study presents an eco-friendly approach to treat contaminated and turbid water through the development of cryogels loaded with bioactive compounds derived from Scenedesmus algal extract (ScAE) based on chitosan/poly(vinyl alcohol) (Cs/PVA) matrix. Scenedesmus sp., a green microalga known for its bioactive properties, was cultivated and processed to obtain extracts with coagulation potential. This extract was incorporated into cryogel at concentrations of 2, 4, 6, and 8 mL to improve coagulation and flocculation processes. Physicochemical analyses, including Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), confirmed the successful synthesis and structural integrity of ScAE-loaded cryogels, demonstrating uniform morphology, high porosity, and enhanced mechanical strength with increasing ScAE concentration. Significant results highlight the effectiveness of a 50 mg ScAE-loaded cryogel, which achieved significant reductions in turbidity, from 6 NTU to 1.6 NTU, and total suspended solids (TSS), from 16 mg/L to 6 mg/L, in water samples. The highest concentration cryogel (ScAE-8) also demonstrated a 62 % reduction in nitrate levels, underscoring its capability for broader contaminant removal. These results reveal that the ScAE-loaded cryogels not only provide an effective, biodegradable alternative to conventional chemical coagulants such as alum but also align with green chemistry approaches, potentially providing a sustainable solution for the large-scale water treatment facilities while lowering the negative environmental consequnces.

Enhanced reducing leachate pollution index through electrocoagulation using response surface methodology

Addressing the urgent need to effectively manage landfill leachate as a harmful flow for human health and the environment, this research investigates how electrocoagulation (EC) processes could alleviate the pollution potential of leachate. So far, no experimental study has been carried out on reducing the leachate pollution index (LPI) under the EC process. For this purpose, in this novel research, the LPI was utilized as a key metric to evaluate the efficiency of the treatment process. Central Composite Design (CCD) as a subset of Response Surface Methodology (RSM) was applied to enhance the LPI parameters decreasing percentage. The data were analyzed by analysis of variance and multivariate regression and 3D plots assessed variable interactions. Under optimal conditions, it showed removal of 97.48 % for COD, 91.42 % for BOD5, 98.52 % for N-NH3, and 91.6 % for TDS. Significant reductions were observed in 94.81 % TKN, 87.20 %, 82.80 %, 96.66 %, and 99.28 %, 99.18 %, and 96.56 % for TKN, Cl-, CN-, As, Cr, Zn, and Ni, respectively. Moreover, the kinetics of COD removal indicated that it follows a first-order model. Thus, based on experimental results, the LPI of raw leachate decreased from 38.06 to 7.22 (81 % decrease) under the EC treatment method. The study indicated that the EC treatment method successfully reduced leachate pollution and met the leachate discharge standard.

Cytogenotoxicity of raw and treated dairy manure slurry by two-stage chemical and electrocoagulation: An application of the Allium cepa bioassay

Livestock farming is an essential agricultural practice. However, the improper management of livestock wastes and discharge of untreated or partially treated livestock manure slurry poses significant environmental problems. In this study, we aimed to compare the cytogenotoxic potential of untreated and treated dairy manure slurry treated with a two-stage chemical and electrocoagulation (EC) using the Allium cepa bioassay. The A. cepa bioassay is a well-established standard tool for assessing the cytogenotoxic effects of environmental contaminants, especially those that are occurred as complex contaminant mixtures. The dairy manure slurry was subjected to chemical treatment utilizing polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) at optimized conditions, followed by EC utilizing either aluminum (Al) or steel anodes. The treated and untreated samples were then evaluated for their potential cytogenotoxicty using the A. cepa bioassay, by measuring the nuclear abnormalities (NAs) and chromosomal aberrations (CAs), along with the mitotic indices (MIs). Our findings revealed a significant reduction in cytogenotoxic indicators in the treated liquid fraction compared to the untreated dairy manure slurry. Specifically, the frequency of total NAs showed a significant reduction from 154 ‰ to 37 ‰ when the dairy manure slurry was treated with chemical coagulation followed by EC utilizing an Al anode. Moreover, the MI exhibited a significant improvement from 7 ‰ to 123 ‰, suggesting the mitigation of toxic effects. These results collectively demonstrate the effectiveness of the two-stage chemical and EC treatment under optimal conditions in treating diary manure slurry while reducing its cytogenotoxicity for living systems. The A. cepa bioassay proved to be a sensitive and reliable method for assessing the toxicity of the treated samples. The efficient solid-liquid separation and the reduction of toxicity in the liquid fraction for biological systems achieved through this treatment process highlight its potential for sustainable management of livestock waste and the preservation of water quality. Nevertheless, further studies are required to assess the toxicity of solid fraction.