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This study was aimed at predicting greywater reuse in a municipality of a developing country using the theory of planned behaviour (TPB). It sought to identify the beliefs that influence people’s intentions to reuse greywater for potable and nonpotable purposes. Residents within the municipality completed a questionnaire designed with the TPB constructs and other demographic data. Results revealed an excellent fit for potable reuse intention and a mediocre fit for nonpotable reuse intentions. Attitudes and behavioural control were the constructs that significantly influenced intentions to reuse greywater for both potable and nonpotable purposes. Location of the source of water to the respondents and level of education were introduced as background factors. Location of the source of water had no significant direct or indirect influence on intentions to reuse greywater for potable or nonpotable purposes. Level of education had a nonsignificant indirect and direct effect on intentions to reuse greywater for potable purpose but is mediated through attitudes and perceived behavioural control for nonpotable reuse intentions. Strategies aimed at promoting greywater reuse should be targeted at a specific reuse option and not a wholesale intervention that is expected to address all reuse interventions. [ABSTRACT FROM AUTHOR]

The relationship between sunlight effect, algal biomass and faecal coliform inactivation in wastewater pond treatment systems is still not clearly understood. Increased pH and dissolved oxygen concentration in treatment ponds results in an increased destruction of faecal coliforms. Increased algal growth however results in a decreased destruction of faecal coliforms due to light attenuation. Algae also releases variable amounts and types of organic matter at various rates and quantities depending on environmental conditions and this can either aid or retard faecal bacteria destruction. We investigated the effect of algal density on faecal coliform destruction under field conditions in sunlight and darkness and how this can be affected by light intensity. In darkness, increased inactivation of faecal coliform occurred with increasing algal density. Rates of decay of faecal coliforms were much faster in sunlight than in darkness even in the absence of algae. In sunlight, rates of decay of faecal coliforms increased with increasing algal density up to a chlorophyll-a concentration of 1.3 ± 0.1 mg/L after which rates of decay decreased. Increased decay rates of faecal coliforms occurred with increasing light intensity or light input. With decreased light input of 20% of 213 W/m2, the optimum algal density for maximum faecal coliform decay decreased to a value which is 6–7 times the value of that under normal insolation of 213 W/m2. It is recommended that in future studies relating to the assessment of performance and estimation of rate ofEscherichia colior faecal coliform inactivation, one of the parameters that need to be reported as well is the insolation. [ABSTRACT FROM AUTHOR]

The biosorption properties ofCocos nuciferashell andMoringa oleiferaseeds for Pb(II) were investigated under batch mode. The optimum pH values obtained for the removal of Pb(II) by theCocos nuciferashell and theMoringa oleiferaseeds were 5 and 2, respectively. The equilibrium biosorption capacities obtained were 2.3 mg g−1 (Moringa oleiferaseeds) and 1.6 mg g−1 (Cocos nuciferashell). The Freundlich isotherm model described the removal of Pb(II) by the biosorbents better than the Langmuir model. TheCocos nuciferashell sorbed 83.34% of the Pb(II) ions in 30 min, while 94.03% was sorbed by theMoringa oleiferaseeds in the same time. The results indicated a fast kinetics for Pb(II) sorption by the biosorbents investigated. The biosorption of Pb(II) ontoCocos nuciferashell andMoringa oleiferaseeds followed the pseudo second-order kinetics withR2values of 0.9997 and 0.9999, respectively. The second-order rate constant (k2) obtained were 0.205 g mg−1min−1(Cocos nuciferashell) and 0.067 g mg−1min−1(Moringa oleiferaseeds). The results indicate that intraparticle diffusion controls the rate of biosorption in this study. This study shows thatCocos nuciferashell andMoringa oleiferaseeds can be important low-cost biosorbents for Pb(II) ions. [ABSTRACT FROM AUTHOR]

Sorption is a viable treatment technology for copper-rich gold mine tailings wastewater. For continuous application, the sorbent should be regenerated with an appropriate desorbent, and reused. In this study, the sequential sorption/desorption characteristics of Cu(II) on coconut shell (CS) and iron oxide coated sand (IOCS) were determined. In batch assays, CS was found to have a Cu(II) uptake capacity of 0.46 mg g−1and yielded a 93% removal efficiency, while the IOCS had a Cu(II) uptake capacity and removal efficiency of 0.49 mg g−1and 98%, respectively. Desorption experiments indicated that HCl (0.05 M) was an efficient desorbent for the recovery of Cu(II) from CS, with an average desorption efficiency of 96% (sustained for eight sorption and desorption cycles). HCl (0.05 M) did not diminish the CS's ability to sorb copper even after eight sorption/desorption cycles, but completely deteriorated the iron oxide structure of the IOCS within six cycles. This study showed that CS and IOCS are both good sorbents for Cu(II); but cyclical sorption/desorption using 0.05 M HCl is only feasible with CS. [ABSTRACT FROM PUBLISHER]

This study compared the effectiveness of different biosorbents, viz. materials commonly present in natural treatment systems ( Scenedesmus quadricauda and reed) and commonly produced fruit wastes (orange and banana peel) to remove Cr(III) and Cr(VI) from a synthetic wastewater simulating tannery wastewater. The Cr(III) removal efficiency followed the order S. quadricauda > orange peel > banana peel > reed, whereas the Cr(VI) removal followed the order banana peel > S. quadricauda > reed > orange peel. The chromium biosorption kinetics were governed by the intraparticle diffusion mechanism. Isotherm data obtained using the different biosorbents were fitted to the Langmuir, Freundlich, and SIPS models, revealing that the experimental data followed most closely the monolayer sorption theory-based Langmuir model than the other models. The maximum Cr(III) sorption capacity, calculated using the Langmuir model, was found to be 12 and 9 mg/g for S. quadricauda and orange peel, respectively, and the maximum Cr(VI) sorption capacity calculated for banana peel was 3 mg/g. The influence of biosorbent size, pH, solid-liquid ratio, and competing ions were examined for Cr(III) biosorption by S. quadricauda and orange peel and for Cr(VI) sorption by banana peel. The solution pH was found to be the most influential parameter affecting the biosorption process: whereas pH 5 was found to be optimum for maximum removal of Cr(III), Cr(VI) was best removed at a pH as low as 3. Interference to chromium sorption by various ions revealed that Cr(III) binding onto orange peel occurs through electrostatic forces, whereas Cr(VI) binding onto banana peel through non-electrostatic forces. [ABSTRACT FROM AUTHOR]

The physical and chemical qualities of the process effluent and the tailings dam wastewater of AngloGold-Ashanti Limited, a gold mining company in Ghana, were studied from June to September, 2010. The process effluent from the gold extraction plant contains high amounts of suspended solids and is therefore highly turbid. Arsenic, copper and cyanide were identified as the major pollutants in the process effluent with average concentrations of 10.0, 3.1 and 21.6 mg L, respectively. Arsenic, copper, iron and free cyanide (CN) concentrations in the process effluent exceeded the Ghana EPA discharge limits; therefore, it is necessary to treat the process effluent before it can be discharged into the environment. Principal component analysis of the data indicated that the process effluent characteristics were influenced by the gold extraction process as well as the nature of the gold-bearing ore processed. No significant correlation was observed between the wastewater characteristics themselves, except for the dissolved oxygen and the biochemical oxygen demand. The process effluent is fed to the Sansu tailings dam, which removes 99.9 % of the total suspended solids and 99.7 % of the turbidity; but copper, arsenic and cyanide concentrations were still high. The effluent produced can be classified as inorganic with a high load of non-biodegradable compounds. It was noted that, though the Sansu tailings dam stores the polluted effluent from the gold extraction plant, there will still be serious environmental problems in the event of failure of the dam. [ABSTRACT FROM AUTHOR]

Adsorption kinetic studies are of great significance in evaluating the performance of a given adsorbent and gaining insight into the underlying mechanism. This work investigated the sorption kinetics of Cu(II) on to coconut shell and Moringa oleifera seeds using batch techniques. To understand the mechanisms of the biosorption process and the potential rate-controlling steps, kinetic models were used to fit the experimental data. The results indicate that kinetic data were best described by the pseudo-second-order model with correlation coefficients (R 2) of 0.9974 and 0.9958 for the coconut shell and Moringa oleifera seeds, respectively. The initial sorption rates obtained for coconut shell and Moringa oleifera seeds were 9.6395×10−3 and 8.3292×10−2 mg g−1 min−1, respectively. The values of the mass transfer coefficients obtained for coconut shell (1.2106×10−3 cm s−1) and Moringa oleifera seeds (8.965×10−4 cm s−1) indicate that the transport of Cu(II) from the bulk liquid to the solid phase was quite fast for both materials investigated. The results indicate that intraparticle diffusion controls the rate of sorption in this study; however, film diffusion cannot be neglected, especially at the initial stage of sorption. [ABSTRACT FROM PUBLISHER]

This paper presents a literature review of the quality of greywater generated in different, especially developing, countries, constituents found in greywater, some treatment systems, natural materials for treatment, some reuse strategies and public perception regarding greywater reuse. The review shows that generation rates are mostly influenced by lifestyle, types of fixtures used and climatic conditions. Contaminants found in greywater are largely associated with the type of detergent used and influenced by other household practices. Many of the treatment systems reviewed were unable to provide total treatment as each system has its unique strength in removing a group of targeted pollutants. The review revealed that some naturally occurring materials such as Moringa oleifera, sawdust, can be used to remove targeted pollutants in greywater. The study further showed that user perceptions towards greywater treatment and reuse were only favourable towards non-potable purposes, mostly due to perceived contamination or lack of trust in the level of treatment offered by the treatment system. [ABSTRACT FROM AUTHOR]