Release of colloids in saturated porous media under transient hydro-chemical conditions: A pore-scale study

The deposition and consequent release of colloids pose a significant challenge to the environment, groundwater quality and human health. Subsurface soil contains numerous types of colloids that exhibit a diverse range of interaction favorability with the soil grains and their impact on release behavior remains unclear. The objective of this study was to investigate, at the pore-scale, the impact of colloid interaction favorability on colloid deposition and subsequent release in response to perturbations of flow rate and solution chemistry in saturated porous media. Pore-scale experiments were conducted using a micromodel that is geometrically representative of a real sand-stone rock. Favorable, medium-favorable and unfavorable colloids (i.e., repulsion absent, repulsion at long-range of separation distances and attraction absent with the micromodel surface, respectively) were deposited in the micromodel and then a series of colloid release experiments were conducted at different conditions including increasing the flow rate, decreasing the ionic strength and increasing the solution pH. Favorable colloids exhibited extensive deposition on the collector center where the flow streamlines are parallel to the collector surface, as adhesion forces overcome hydrodynamic forces. However, at medium and high ionic strength, deposition in Forward Flow Stagnation Zone (FFSZ) was dominant for unfavorable colloids as the hydrodynamic forces are negligible. Pore-scale images showed that, upon perturbations in flow rate and solution chemistry, colloids that were initially deposited on collector centers were more susceptible to release as compared to colloids that were initially deposited in FFSZs. The negligible hydrodynamic drag forces in FFSZ and deep primary minimum interaction at short separation distances were the major factors that hindered the release of colloids in FFSZ under transient hydro-chemical conditions. The intensity of colloid deposition and release decreases as the favorability of colloids decreases and as the ionic strength decrease for unfavorable colloids. This study provides a clear insight to the pore-scale colloid deposition and release mechanisms during transient hydro-chemical conditions that help in the modeling of environmental and engineering applications including managed aquifer recharge, groundwater contamination and wastewater treatment processes. 2021 The Author(s)Open Access funding provided by the Qatar National Library. This publication was made possible by partial funding from NPRP grant #NPRP8-594-2-244 from the Qatar National Research Fund (a member of Qatar Foundation). Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the view of funding agencies. Safna Nishad was funded by the Graduate Assistantship program at Qatar University. The authors would like to thank the Center for Advanced Materials (CAM) at Qatar University for help in Zeta Potential Analysis.Scopu

Poultry Slaughterhouse Wastewater Treatment Using Submerged Fibers in an Attached Growth Sequential Batch Reactor

In this study, a sequential batch reactor (SBR) with different types of fibers was employed for the treatment of poultry slaughterhouse wastewater. Three types of fibers, namely, juite fiber (JF), bio-fringe fiber (BF), and siliconised conjugated polyester fiber (SCPF), were used. Four SBR experiments were conducted, using the fibers in different reactors, while the fourth reactor used a combination of these fibers. The treatment efficiency of the different reactors with and without fibers on biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia-nitrogen (NH₃-N), phosphorus (P), nitrite (NO₂), nitrate (NO₃), total suspended solids (TSS), and oil-grease were evaluated. The removal efficiency for the reactors with fibers was higher than that of the reactor without fibers for all pollutants. The treated effluent had 40 mg/L BOD₅ and 45 mg/L COD with an average removal efficiency of 96% and 93%, respectively, which meet the discharge limits stated in the Environmental Quality Act in Malaysia

Optimization of Coagulation-Flocculation Process of Landfill Leachate by Tin (IV) Chloride Using Response Surface Methodology

Landfill leachate is highly polluted and generated as a result of water infiltration through solid waste produced domestically and industrially. This study investigated the applicability of the response surface methodology (RSM) to optimize the removal performances of chemical oxygen demand (COD), color, and suspended solids (SS) from landfill leachate by coagulation process using Tin tetrachloride pentahydrate. The leachate samples were collected from Alor Pongsu Landfill (APLS) in Perak, Malaysia. Before starting the experiments, general characterization was carried out for raw leachate samples to investigate their physical and chemical properties. The effects of the dosage and pH of SnCl4 on the removal performances were evaluated as well. An ideal experimental design was performed based on the central composite design (CCD) by RSM. In addition, this RSM was used to evaluate the effects of process variables and their interaction toward the attainment of their optimum conditions. The statistical design of the experiments and data analysis was resolved using the Design-Expert software. Further, the range of coagulant dosage and pH was selected based on a batch study which was conducted at 13000 mg/L to 17000 mg/L of SnCl4 and pH ranged from 6 to 10. The results showed that the optimum pH and dosage of SnCl4 were 7.17 and 15 g/L, respectively, where the maximum removal efficiency was 67.7% for COD and 100% for color and SS. The results were in agreement with the experimental data with a maximum removal efficiency of 67.84 %, 98.6 %, and 99.3%, for COD, color, and SS, respectively. Overall, this study verified that the RSM method was viable for optimizing the operational condition of the coagulation-flocculation process

Effectiveness of Oil Palm Frond Activated Carbon for Removing COD, Color and Fe from Landfill Leachate

This study examined the applicability of oil palm frond-activated carbon (OPF-AC) as adsorbent in the treatment of landfill leachate. OPF-AC was prepared by mixing granular OPF with an aqueous solution composed of distilled water and zinc chloride (ZnCl2) at different ratios. Batch experiment studies were carried out to investigate the optimum OPF-AC dosage as well as the optimum shaking time. The optimum condition was achieved at 1.2 g of OPF-AC dosage and 50 minutes of shaking time. The highest removals of COD, color and Fe (77%, 75% and 69%, respectively) were obtained at the optimum condition. Meanwhile, the adsorption capacities were 146.93 mg/g (COD), 56.43 mg/g (color) and 0.11 mg/g (Fe). The increase in adsorbent dosage also resulted in a larger free surface area and exchangeable binding sites. However, the unsaturation of adsorption sites during the adsorption process resulted in a slight drop in removal efficiency of COD, color, and Fe. Furthermore, due to the aggregation and overcrowding of adsorbent particles, the use of a greater amount of adsorbent dosage imposed particle interactions.

Investigation of Air Pollution Impact on Kinta River Water Quality at a Tropical Region

Critical air quality levels lead to an unhealthy environment which disrupts physical activities and human health. Wet deposition of air pollutants might cause a high concentration of water pollution due to rain water washout of nitrate and particulate matter (PM). This study aimed to investigate the impacts of air pollutants deposition on river water quality in Malaysia. The methodology involved in the analysis of secondary data (January to December 2013) for air quality and river water quality using factor, correlation, and regression. Parameters of air quality were PM10, Nitrate (NO3), ozone (O3) and temperature while water quality data were turbidity, Nitrate and PM10 (Ca, As, Hg, Cd, Cr, Pb, Zn, Cl, Fe, K, Mg, Na). The results show that there were positive correlations between air quality indicators and Kinta river water quality parameters. Correlation matrix shows that in terms of turbidity, air and water data were having 96% similarities. Regarding Nitrate concentrations, air and water records had only 30% of correlation matrix, which can be due to other sources of Nitrate which was agriculture activities near Kinta River. The factor analysis results showed that PM was the main contributor to river water quality particles with 94%. © 2020 Published under licence by IOP Publishing Ltd

The removal efficiency of total coliform, escherichia coli, suspended solids, uv254 and colour using zeliac filter in riverbank filtration system

Addition of composite adsorbent Zeliac to a riverbank filtration system can enhance the removal of micropollutants in polluted river water. This paper aims to investigate the potential use of Zeliac to remove pollutants, such as total coliform, Escherichia coli, suspended solids (SSs), UV254 and colour, from the Sungai Kerian River. Two columns filled with Zeliac of different granular sizes were established and continuously run for 15 days. Maximum SS removals of 93% and 98% were recorded for Zeliac with granular sizes of 1.18–2 mm and 0.42–0.6 mm, respectively. Meanwhile, 99%–100% of total coliform was removed from the system, and no E. coli was detected in the effluent up to 15 h of the experiments. High removal efficiencies were also recorded for UV254 (>80%) and colour (>90%). Granular size showed no significant effect on the removal of the selected parameters, especially total coliform and E. coli. Zeliac showed good potential as an adsorbent to improve water treatment. © IWA Publishing 2020

Poultry Slaughterhouse Wastewater Treatment Using Submerged Fibers in an Attached Growth Sequential Batch Reactor

In this study, a sequential batch reactor (SBR) with different types of fibers was employed for the treatment of poultry slaughterhouse wastewater. Three types of fibers, namely, juite fiber (JF), bio-fringe fiber (BF), and siliconised conjugated polyester fiber (SCPF), were used. Four SBR experiments were conducted, using the fibers in different reactors, while the fourth reactor used a combination of these fibers. The treatment efficiency of the different reactors with and without fibers on biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia-nitrogen (NH₃-N), phosphorus (P), nitrite (NO₂), nitrate (NO₃), total suspended solids (TSS), and oil-grease were evaluated. The removal efficiency for the reactors with fibers was higher than that of the reactor without fibers for all pollutants. The treated effluent had 40 mg/L BOD₅ and 45 mg/L COD with an average removal efficiency of 96% and 93%, respectively, which meet the discharge limits stated in the Environmental Quality Act in Malaysia

Potential Use of Dimocarpus longan Seeds as a Flocculant in Landfill Leachate Treatment

Landfill leachate is a highly polluted and generated from water infiltration through solid waste produced domestically and industrially. In this study, a coagulation-flocculation process using a combination of Polyaluminium chloride (PACl) as a coagulant and Dimocarpus longan seed powder (LSP) as coagulant aid was used in treating landfill leachate. LSP has been tested as the main coagulant and as coagulant aid with PACl. As the main coagulant, the optimum dosage and pH for PACl were 5 g/L and 6, respectively, with removal efficiencies of 67.44%, 99.47%, and 98% for COD, SS, and color, respectively. For LSP as the main coagulant, results show that LSP is not effective where the removal efficiencies obtained for COD, SS, and color were 39.40%, 22.20%, and 28.30%, respectively, with the optimum dosage of 2 g/L and pH 4. The maximum removal efficiencies of COD, SS, and color were 69.19%, 99.50%, and 98.80%, respectively, when LSP was used as coagulant aid with PACl. Results show that using LSP as coagulant aid was found to be more effective in the removal of COD, SS, and color with less PACl dosage. The PACl dosage was decreased from 5 to 2.75 g/L when LSP was used as a coagulant aid. Cost estimation for using PACl alone and using LSP as the coagulant aid showed a reduction in the cost of approximately 40% of the cost of using PACl alone. Overall, this study confirmed the efficiency of LSP to be used as a natural coagulant aid in leachate treatment

Potential use of algae for the bioremediation of different types of wastewater and contaminants: Production of bioproducts and biofuel for green circular economy

Remediation by algae is a very effective strategy for avoiding the use of costly, environmentally harmful chemicals in wastewater treatment. Recently, industries based on biomass, especially the bioenergy sector, are getting increasing attention due to their environmental acceptability. However, their practical application is still limited due to the growing cost of raw materials such as algal biomass, harvesting and processing limitations. Potential use of algal biomass includes nutrients recovery, heavy metals removal, COD, BOD, coliforms, and other disease-causing pathogens reduction and production of bioenergy and valuable products. However, the production of algal biomass using the variable composition of different wastewater streams as a source of growing medium and the application of treated water for subsequent use in agriculture for irrigation has remained a challenging task. The present review highlights and discusses the potential role of algae in removing beneficial nutrients from different wastewater streams with complex chemical compositions as a biorefinery concept and subsequent use of produced algal biomass for bioenergy and bioactive compounds. Moreover, challenges in producing algal biomass using various wastewater streams and ways to alleviate the stress caused by the toxic and high concentrations of nutrients in the wastewater stream have been discussed in detail. The technology will be economically feasible and publicly accepted by reducing the cost of algal biomass production and reducing the loaded or attached concentration of micropollutants and pathogenic microorganisms. Algal strain improvement, consortium development, biofilm formation, building an advanced cultivation reactor system, biorefinery concept development, and life-cycle assessment are all possible options for attaining a sustainable solution for sustainable biofuel production. Furthermore, producing valuable compounds, including pharmaceutical, nutraceutical and pigment contents generated from algal biomass during biofuel production, could also help reduce the cost of wastewater management by microalgae. © 2022 Elsevier Lt