Editorial: Higher education well-being: A balancing Act

Introductory Article and no abstract included

Enhanced Biogas Production through Anaerobic Co-Digestion of Agricultural Wastes and Wastewater: A Case Study in South Africa

Received: 6 March 2023. Accepted: 30 May 2023.The authors wish to express their appreciation to the Green Engineering Research Group at the Durban University of Technology for proving necessary equipment to make this study a success. Also, the eThekwini Municipality and the REFFECT Africa project team for their kind assistance and support.The sustainable management of agricultural wastes (AWs) and their valorization for biogas production offer promising alternatives to fossil fuels and contribute to environmentally responsible waste management strategies. This study examines the anaerobic co-digestion (Co-AD) of various AWs, including apples, bananas, carrots, butternuts, and potatoes, combined with wastewater (WW) from a local fruit and vegetable market, using activated sludge (AS) as the inoculum. The biomethane potential test (BMP) was performed in 1L capacity digesters with an 80% working volume and maintained at 40℃ over a 21-day period. A mixing ratio of 1:1 (% w/w) between WW and AWs and 1:2 between the cosubstrates and inoculum was utilized. Biogas production was monitored daily to evaluate the effectiveness of the Co-AD process. The control group yielded a total production of 450 mL/day, while the apple and banana substrates demonstrated the highest biogas output at 595 mL/day and 585 mL/day, respectively. The potato substrate generated 525 mL/day, mixed AWs produced 485 mL/day, and butternut and carrot substrates resulted in 485 mL/day and 475 mL/day, respectively. These findings suggest that the Co-AD of AWs and WW, in combination with AS, presents a viable and eco-friendly approach to enhanced biogas production

Correlations for the Prediction of NTU and Mass Transfer Coefficient for a VPE

Liquid-liquid extraction is the separation of the constituents of a liquid solution by contact with another insoluble liquid and belongs to the class of countercurrent diffusional separation processes, where it ranks second in importance to distillation. There are many different types of columns that are available for liquid-liquid extraction and the reciprocating column and vibrating plate column are two types of mechanically aided columns. This paper aims at developing appropriate correlations for the prediction of NTU/HETS and the mass transfer coefficient, kox for the VPE based on the agitation level of the plates (af – the product of frequency and amplitude of the plate motion), the plate spacing and the flow rates which will allow for the simplification in the design of this type of column

Characteristics of greywater from different sources within households in a community in Durban, South Africa

The reuse of greywater is steadily gaining importance in South Africa. Greywater contains pollutants that could have adverse effects on the environment and public health if the water is not treated before reuse. Successful implementation of any greywater treatment process depends largely on its characteristics in terms of the pollutant strength. This study investigated the physico-chemical characteristics of greywater from different sources within 75 households in a community in Durban, South Africa. The study was undertaken to create an understanding of greywater quality from different sources within and between households. Greywater samples were collected from the kitchen, laundry and bathing facilities within each of the households. The samples were analysed for: pH, conductivity, turbidity, total solids, chemical oxygen demand (COD) and biological oxygen demand (BOD). There was a significant difference in the parameters analysed between the greywater from the kitchen compared with the greywater from the bathtub/shower and laundry. It was also observed that the characteristics of greywater from the different households varied considerably. The characteristics of the greywater obtained in this study suggest that the greywater generated cannot be easily treatable using biological treatment processes and/or technologies due to the very low mean BOD : COD ratio (<0.5)

Effects of a polymeric organic coagulant for industrial mineral oil wastewater treatment using response surface methodology (RSM)

In this study, treatment of a local South African oil refinery effluent using a coagulation flotation process is designed using&nbsp;response surface methodology (RSM). A Box-Behnken design (BBD) implementing the RSM is applied to evaluate the effects&nbsp;and interactions of three operating parameters, viz., pH, coagulant dosage and flotation time, on the treatment of mineral oil&nbsp;wastewater (MOW). Polyacrylamide (Zetag-FS/A50), which is a water-soluble compound, is applied to enhance the adsorption&nbsp;mechanism and intermolecular bridging to minimise the amount of oil droplets. In addition, due to the monomeric nature&nbsp;and the charge density of the Zetag-FS/A50, its efficiency was evaluated to serve as an alternative coagulant for the pretreatment&nbsp;of the MOW. The removal of chemical oxidation demand (COD), soap oil and grease (SOG), total suspended solids&nbsp;(TSS) and turbidity from the MOW were used as the response variables for the coagulation flotation process. This was done&nbsp;with a standard dissolved air flotation jar test. The results show that the actual COD, SOG, TSS and turbidity percentage&nbsp;removal at optimised conditions with a coagulant dosage of 50 mg/L were 82%, 83%,70% and 83% respectively, while the&nbsp;predicted response was 92%, 96%, 73% and 87% for COD, SOG, TSS and turbidity, respectively. The analysis of variance&nbsp;(ANOVA) showed that the proposed models are significant at a 95% confidence level. A quadratic model was generated&nbsp;for response variables COD and SOG, while TSS and turbidity produced a linear model. The models fitted well with the&nbsp;experimental data with correlation coefficients (actual R2) of 0.94 for COD, 0.91 for SOG, 0.81 for TSS, and 0.75 for turbidity.&nbsp;The outcome of the study shows that the RSM has merit to optimise and identify the most important factor to control and the&nbsp;Zetag-FS/A50 coagulant has the potential to adsorb the oil droplets in order to enhance the treatment efficiency of the process

Evaluation of different polymeric coagulants for the treatment of oil refinery wastewater

Wastewater from oil refinery industries has major pollution potentials with mutagenic and toxic compounds. Due to water scarcity in South Africa, oil refinery industries are compelled to find appropriate technology to treat their wastewater for reuse. With regards to this, most of the chemo-physical treatment processes are inadequate and are faced with major environmental and economic challenges. Therefore, this study aimed to find replaceable and cost-effective coagulants to the conventional coagulant for the treatment of a local South Africa oil refinery wastewater using dissolved air flotation (DAF) Jar tests. Three polymeric coagulants for the removal of turbidity, total suspended solids, chemical oxygen demand, and soap oil and grease (SOG) were investigated. At defined experimental conditions of recycle ratio (10%), air saturator pressure (350 kPa) and pH at 5, each coagulant was evaluated from a dosage of 10 mg/L to 50 mg/L. Above 80% of the aforementioned oily pollutants were removed at the coagulant dosage of 50 mg/L. Among the coagulants evaluated, PASS was found as the most suitable alternative coagulant to alum, to enhance and aggregate the air bubble–oil droplet interface for easy separation by the DAF. From the results, PASS is foreseen as promising and economical for pre-treatment of industrial wastewater, which is due to its lower cost and easy degradability

Modelling competitive BTEX compounds removal from industrial wastewater in packed-bed columns using polystyrenic resin

The competitive simultaneous removal of petrochemical hydrocarbons including benzene, toluene, ethylbenzene and isomers of xylene (BTEX) from an aqueous solution by polystyrenic resin (PAD 910) was investigated at dynamic conditions in a packed bed column. The column was operated under conditions of bed length (Z = 30–90 cm), flow rate (Q = 18.5–53.5 cm/min), bed diameter (D = 2.5–5 cm) and initial concentration of (C0 = 5–14.5 mg/l) to investigate the adsorption characteristics of BTEX at an influent pH of 6.85. There was evidence of improved column performance with increasing operating height and decreased flow rate. Breakthrough curves of fixed-bed adsorption process were developed by the constant-pattern approach using a constant driving force model in the liquid phase. A fairly good fit to the experimental data was obtained using the constant-pattern approach and a Langmuir isotherm model obtained from previous work. In addition, a prediction of volumetric mass transfer coefficient correlation in the liquid phase was suggested. Desorption from polystyrenic resin adsorbed with BTEX was investigated by using two different organic solvents as desorbates

Prospects of Synthesized Magnetic TiO2-Based Membranes for Wastewater Treatment: A Review

Global accessibility to clean water has stressed the need to develop advanced technologies for the removal of toxic organic and inorganic pollutants and pathogens from wastewater to meet stringent discharge water quality limits. Conventionally, the high separation efficiencies, relative low costs, small footprint, and ease of operation associated with integrated photocatalytic-membrane (IPM) technologies are gaining an all-inclusive attention. Conversely, photocatalysis and membrane technologies face some degree of setbacks, which limit their worldwide application in wastewater settings for the treatment of emerging contaminants. Therefore, this review elucidated titanium dioxide (TiO2), based on its unique properties (low cost, non-toxicity, biocompatibility, and high chemical stability), to have great potential in engineering photocatalytic-based membranes for reclamation of wastewater for re-use. The environmental pathway of TiO2 nanoparticles, membranes and configuration types, modification process, characteristics, and applications of IPMs in water settings are discussed. Future research and prospects of magnetized TiO2-based membrane technology is highlighted as a viable water purification technology to mitigate fouling in the membrane process and photocatalyst recoverability. In addition, exploring life cycle assessment research would also aid in utilizing the concept and pressing for large-scale application of this technology

The applicability of nanofiltration for the treatment and reuse of textile reactive dye effluent

CITATION: Chollom, M. N. et al. 2015. The applicability of nanofiltration for the treatment and reuse of textile reactive dye effluent. Water SA, 41(3), doi:10.4314/wsa.v41i3.12.The original publication is available at http://www.wrc.org.zaThe main aim of the study was to test the feasibility of using nanofiltration (NF) processes for the treatment of reactive dyebath effluents from the textile industry, in order to recover the water and chemicals (salts) for reuse purposes. The study of the reusability of nanofiltered water for dyeing has been given little or no attention. About 30% of reactive dyes remain unfixed on fibres; the unfixed dyes are responsible for the colouration in effluents. Membrane processes were employed to treat reactive dye-bath effluents to recover the salts and water. Investigations were conducted firstly with ultrafiltration (UF) used as a pretreatment for NF. Secondly, evaluations were performed for 2 types of NF membranes (SR90 and NF90), in terms of quality of permeate produced and fluxes achieved for 2 different samples of effluent. The effect of cleaning on membrane performance was assessed. A reusability test was carried out on both permeate samples for dyeing light and dark shade recipes. The use of UF as pre-treatment to NF resulted in rejection of colloidal substances > 90% and a 15% flux improvement. Permeate from NF90 had a conductivity of 76 µS/cm and total organic carbon (TOC) of 20 mg/ℓ, as compared to SR90 which had a conductivity of 8.3 mS/cm and a TOC of 58 mg/ℓ. Light shade from NF90 gave satisfactory results on dyeing, with no colour difference. However a variation in colour was noticed when the medium sample was used to dye the light shade. Both NF permeates gave satisfactory results when used to dye the dark shades. Permeate from NF90 was within the accepted range for reuse, while permeate from SR90 had a higher salt recovery. Chemical cleaning resulted in 80% flux recovery. From the reusability test it was concluded that permeate from NF90 met the reuse criteria for feed water to the dye bath.Publisher's versio