Jabulani R. Gumbo

An update on synthetic dyes adsorption onto clay based minerals: A state-of-art review

Dyes are growing to be a problematic class of pollutants to the environment. The disposal of dyes in water resources has bad aesthetic and health effects, hence the need to remove them from the environment. The need for treatment methods that are effective and low in price is rising hence a lot of research interest is being diverted towards adsorbents that are cheap, preferable naturally occurring materials like clays. In most reported dye adsorption studies, limited information on the relationship between characterization results with adsorbent performance on dye removal has been given. This review article seeks to report on the link between the adsorption characteristics of the clays and their adsorption capacities and to gather information on the modifications done on clays to improve their adsorption capacities. A critical analysis of the different mechanisms involved during the decolouration process and their application for dye removal has been discussed in detail in this up-to-date review. From a wide range of consulted literature review, it is evident that some clays have appreciable adsorption capacities on top of being widely available. It was also noted that several parameters like contact time, dosage, concentration, temperature and pH affect the removal of dyes. Furthermore, the application of clay minerals for decolourising water represents economic viable and locally available materials that can be used substantially for pollution control and management. Conclusions were also drawn and suggestions for future research perspectives are proposed.

Assessment of heavy metals in municipal sewage sludge: a case study of Limpopo province, South Africa.

Heavy metals in high concentrations can cause health and environmental damage. Nanosilver is an emerging heavy metal which has a bright future of use in many applications. Here we report on the levels of silver and other heavy metals in municipal sewage sludge. Five towns in Limpopo province of South Africa were selected and the sludge from their wastewater treatment plants (WWTPs) was collected and analysed. The acid digested sewage sludge samples were analysed using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) methods. The concentrations of silver found were low, but significant, in the range 0.22 to 21.93 mg/kg dry mass. The highest concentration of silver was found in Louis Trichardt town with a concentration of 21.93 ± 0.38 mg/kg dry mass while the lowest was Thohoyandou with a concentration of 6.13 ± 0.12 mg/kg dry mass. A control sludge sample from a pit latrine had trace levels of silver at 0.22 ± 0.01 mg/kg dry mass. The result showed that silver was indeed present in the wastewater sewage sludge and at present there is no DWAF guideline standard. The average Cd concentration was 3.10 mg/kg dry mass for Polokwane municipality. Polokwane and Louis Trichardt municipalities exhibited high levels of Pb, in excess DWAF guidelines, in sludge at 102.83 and 171.87 mg/kg respectfully. In all the WWTPs the zinc and copper concentrations were in excess of DWAF guidelines. The presence of heavy metals in the sewage sludge in excess of DWAF guidelines presents environmental hazards should the sludge be applied as a soil ameliorant.

Knowledge, Attitude and Practices (KAP) Survey on Water, Sanitation and Hygiene in Selected Schools in Vhembe District, Limpopo, South Africa

This study assessed the knowledge, attitude and practices (KAP) of learners on issues related to water, sanitation and hygiene in selected schools in Vhembe District, South Africa. The methodology relied on a questionnaire, an inspection of sanitary facilities and discussion with the school authorities. The data was analyzed using the Statistical Package for Social Science. The study revealed that the level of knowledge about waterborne diseases was relatively high (76.7 ± 1.75%), but knowledge on transmission routes was inadequate. The majority of the respondents had no knowledge when it comes to water-based diseases and their prevention (78.4 ± 1.71%).The attitude and practice on hygiene was also found to be high (91.40 ± 1.16%). Some schools from the urban area had proper handwashing facilities, but there was no soap available. The borehole water quality for rural schools appeared clear, but the microbial quality was unknown. The water supply and sanitation facilities were inadequate in rural schools, with no handwashing areas and no sanitary bins for girls. Some schools had toilets with broken doors which did not offer privacy. The only water tap, located at the centre of the school premises, was not enough for the whole school community.

The health implications of wastewater reuse in vegetable irrigation: a case study from Malamulele, South Africa

Malamulele is located in an arid region where small-scale irrigation with wastewater is rife. A study was conducted to investigate the health implications of wastewater reuse in vegetable irrigation. Results showed that there are potential health hazards associated with this practice. The wastewater contained 103 helminth eggs/100 ml and zero helminth eggs for control group; vegetable wash water had 3 helminth eggs/100 ml for the exposed group and zero for control. The wastewater results exceeded the WHO guidelines whereas the vegetable wash water counts were within the guideline. Stool samples of farmers and their children indicated common infections with hookworm and Giardia lamblia. Hookworm infections were high (42%) among exposed group in comparison to the control group (27.5%). The farmers were able derive their livelihood from the sale of vegetables. The findings suggest that the health risks of using wastewater are real but can be managed by using the incomes that the farmers earn.

Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation

ABSTRACT The quest to reduce fluoride in groundwater to WHO acceptable limit of 1.5 mg/L to prevent diseases such as teeth mottling and skeletal fluorosis was the motivation for this study. Al/Fe oxide-modified diatomaceous earth was prepared and its defluoridation potential evaluated by batch method. The sorbent with pHpzc 6.0 ± 0.2 is very reactive. The maximum 82.3% fluoride removal attained in 50 min using a dosage of 0.3 g/100 mL in 10 mg/L fluoride was almost attained within 5 min contact time; 81.3% being the percent fluoride removal at 5 min contact time. The sorbent has a usage advantage of not requiring solution pH adjustment before it can exhibit its fluoride removal potential. A substantial amount of fluoride (93.1%) was removed from solution when a sorbent dosage of 0.6 g/100 mL was contacted with 10 mg/L fluoride solution for 50 min at a mixing rate of 200 rpm. The optimum adsorption capacity of the adsorbent was 7.633 mg/g using a solution containing initially 100 mg/L fluoride. The equilibrium pH of the suspensions ranged between 6.77 and 8.26 for 10 and 100 mg/L fluoride solutions respectively. Contacting the sorbent at a dosage of 0.6 g/100 mL with field water containing 5.53 mg/L at 200 rpm for 50 min reduced the fluoride content to 0.928 mg/L—a value below the upper limit of WHO guideline of 1.5 mg/L fluoride in drinking water. The sorption data fitted to both Langmuir and Freundlich isotherms but better with the former. The sorption data obeyed only the pseudo-second-order kinetic, which implies that fluoride was chemisorbed.

Willingness to Pay for Water Services in Two Communities of Mutale Local Municipality, South Africa: A Case Study

Abstract The provision of reliable and adequate drinking water services in rural communities is important. Here, the researchers reported on a study that evaluated the respondents’ willingness to pay for water services in the two communities in Mutale Local Municipality, South Africa. The study was accomplished through open-ended questionnaire interviews with selected respondents. The study showed that respondents were dissatisfied with the unreliable water services (89.9%) but were willing to pay for water services to secure reliable water services (95.5%). The respondents with tertiary level education were willing to pay R 150 per month per 6 kilolitres. The maximum 6 kilolitres is the free basic water services that the municipality can provide without collecting water revenues. The following variables: literacy levels; household size of 3 to 6 members; the age of 40; and monthly incomes, had a significant effect (p = 0.005) on the monetary amount and the willingness to pay.

Assessing the environmental context of hand washing among school children in Limpopo, South Africa

ABSTRACT Despite its simplicity and efficacy, the promotion of hand washing for disease prevention remains a challenge, particularly in resource-limited settings. This article reports on a quasi-experimental school-based study that aimed to improve habitual hand washing. Significant increases in hand washing occurred following improvements in hygiene and sanitation facilities (School A: t = 13.86, p = 0.0052). Smaller increases in hand washing occurred following education (School A: t = 2.63; p = 0.012; School B, no infrastructure improvements: t = 1.66, p = 0.239). Health policy and programming need to pay greater attention to the interplay of the structural, social and individual dimensions of unique contextual environments that influence habitual behaviours.

Field Study On Heavy Metal Removal In A Natural Wetland Receiving Municipal Sewage Discharge

Constructed and natural wetlands have been used successfully in the treatment and polishing of municipal wastewater all over the world, including in South Africa. Here we report on the heavy metal removal in a natural wetland that is receiving municipal sewage discharge, Limpopo province, South Africa. The natural wetland is located downstream of Makhado oxidation ponds and is dominated by the reed plant Phragmites australis. The changes in the metal variation from discharge of oxidation ponds to middle section and downstream of the natural wetland was analysed for heavy metals by ICP-MS over a 12 month period. The annual rainfall data were obtained from Agricultural Research Council. The following heavy metals: total chromium, zinc, cadmium and lead were effectively reduced during the passage through the wetland, to levels below the Department of Water & Sanitation (DWS) guidelines for waste water discharge. In contrast, the manganese and iron was reduced slightly above the DWS guideline value during the drier season and was higher during the wet season indicating a contribution of soil and water erosion. With copper it was effectively reduced during the wet and dry seasons with the exception in April, June and September when the downstream section was three times higher than the DWS guideline value. Thus the natural wetland was able to reduce considerable the heavy metals in the municipal discharge during its passage in the wetland. This is able to render the water in downstream of the wetland safe for rural communities to use the water for irrigation purposes.

Calcined magnesite as an adsorbent for cationic and anionic dyes: characterization, adsorption parameters, isotherms and kinetics study

The ability of calcined magnesite for Methylene Blue (MB), Direct Red 81 (DR81), Methyl Orange (MO) and Crystal Violet (CV) dye removal was evaluated in this study. The experiments were designed to test the hypothesis that alkaline earth carbonates can remove dyes from water through a combination of sorption and coagulative reactions involving Mg2+. To achieve that, several operational factors like residence time, dosage, adsorbent concentration and temperature were appraised. The batch study proved that calcined magnesite is effective in the treatment of MB, DR81, CV and MO contaminated water and moreover it performed well in terms of color removal. The adsorption equilibrium data were analysed by the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherm models, and the Dubinin–Radushkevich and Temkin models were found to be the most appropriate fit to MB and MO dyes respectively. The adsorption kinetics process primarily followed the Elovich and Pseudo-second order model, a possible indication that chemisorption was the rate limiting step during the dye uptake process. With the adsorption–desorption cycle repeated four times, the calcined magnesite regeneration efficiency for DR81 and MO loaded dyes remained very high. According to the results of this study, it can be concluded that calcined magnesite can be used effectively for the adsorption of MB, DR81, CV and MO from wastewater.