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Coagulation experiments were done using raw water samples from two treatment plants (herein referred to LMTP and LNTP) in Mauritius in jar tests using Moringa oleifera (MO) extract and Sudfloc. Both coagulant aids reduced alum consumption. Sudfloc was required in low concentration as compared to crude extracts of MO. On samples from LMTP, salt extract of MO (MOSE) was six times more efficient than water extracts of MO (MOWE) with 10 mg/L alum (coagulation efficiency of 50%). Samples from LNTP required lower amounts of coagulant aid. MO extracts increased the organic load but gave better removal of aluminium.

Azo dyes are used in many industries such as carpet manufacturing, textiles, paint, ink, plastics and cosmetics production processes. The coloured industrial effluent can pose serious problems in the aquatic environment. It is possible to get complete mineralisation of organic pollutants in water by photocatalysts. This study was carried out to examine the feasibility to remove supra black-T dye from carpet dyeing wastewater by photocatalytic degradation on Oak charcoal under sunlight. Adsorption efficiency of dye on charcoal at various pH values and photodegradation with ZnO and TiO2 catalysts were studied. The removal efficiency of charcoal alone was 28 mg dye/g charcoal at pH 8 and 25oC in 60 min which was half that of activated charcoal. Photocatalytic degradation and adsorption with TiO2 and ZnO under sunlight was faster and almost complete removal was observed in shorter times.

Batch adsorption studies were conducted to investigate the potential of Acacia nilotica sawdust as biosorbent for removal of basic Swiss blue dye from wastewater. Sawdust was subjected to formaldehyde pretreatment (FSD) and boiling (BSD). Maximum dye removal was observed after 120 min for all conditions – FSD: 97.5% and BSD: 95.9% at pH 6, 50 mgL−1 dye concentration and 0.2 g/50 mL adsorbent dosage. Adsorption was endothermic and was accompanied by an increase in entropy and a decrease in Gibbs free energy for 288?333 K. Equilibrium data fitted excellently with the Langmuir isotherm (FSD: R² &#61 0.9955, BSD: R² &#61 0.9914). Adsorption kinetics was found to follow pseudo-second-order model (R² > 0.99, FSD and BSD). It can be concluded that formaldehyde-treated sawdust (FSD) can be used as a more efficient and low-cost alternative to the chemically untreated sawdust in aqueous solution for Swiss blue dye removal.

The performance of a laboratory-scale sequencing batch reactor (SBR) of 20-litre capacity was evaluated for simultaneous removal of soluble COD (SCOD), NH4+?N and phosphorus by changing the compositions and concentrations of substrates under different combinations of REACT period. The total cycle period of 10 h comprised 0.5 h FILL period, 8 h REACT period, 1 h SETTLE period and 0.5 h IDLE/DRAW period with the react period being divided into two combinations of anoxic (A) and aerobic (O) react period namely (4 h + 4 h) (A/O) and (3 h + 3 h + 2 h) (A/O/A). The initial SCOD concentration was kept constant at 2000 mg/l while the initial NH4+?N concentrations were taken as 90 mg/l and 180 mg/l as N tentatively. Results for total phosphorus accumulation capacity indicated that the A/O/A combination was more conducive to total phosphorus uptake at 90.26 mg P/g MLVSS than the A/O combination in the aerobic reaction period which followed the initial 3-h anoxic react period.

The conventional COD determination through reflux method, although still much in experimental practice for water and wastewater analysis, is time consuming, complex and prone to a number of errors. A simpler, more rapid, environmentally benign but still precise method would hence be more attractive and is, in point of fact, a pressing need. Contextualised within the concept of Green Chemistry, this review discusses a handful of research papers published to date on microwave-assisted COD determination and brings forward the achievable improvements in COD analysis while using this clean analytical technique.

The paper reviews the state-of-the-art technologies on sludge conditioning and stabilisation. Radiation technology, best contextualised within the concept of Green Chemistry, is yet another developing area of sludge pretreatment. Besides revisiting some important aspects of sludge treatment by composting, this review paper also appraises the application of gamma ray and ultrasound irradiations particularly in sludge pretreatment and sludge composting for monitoring, and to some extent improving, the degradation and subsequent stabilisation of sludge constituents. The scientific principle of each type of radiation and selected research work are discussed, and future needs for applied research are eventually outlined.

Samples of textile effluents were subjected to physico-chemical treatment using alum, Polyaluminium Chloride (PAC), and different anionic and cationic acrylamide copolymers. Except for alum, all chemicals were tested individually. Combinations of alum and PAC with different anionic and cationic polyelectrolytes were also tested. Results indicated the anionic polyelectrolyte to be the best polymer when used in combination with inorganic coagulants. 30-40 mg/L PAC and 0.75 mg/L of anionic polymer resulted in the best removals of Chemical Oxygen Demand (COD), Total Suspended Solids (TSS) and Turbidity of 32.0-38.2%, 80.0-85.0% and 25.3-47.0%, respectively. This study indicated that dye-loaded textile wastewater could be treated with blends of inorganic?organic coagulants to reduce the organic load. However, the colour of the wastewater could not be removed.

In this study, the annual generation of Landfill Gas (LFG) and methane using the Scholl-Canyon model have been predicted for 1998-2030 for five scenarios of landfill management at the Mare Chicose landfill in Mauritius. Using the Approved Large-Scale Methodology AM003 and Approved Baseline Methodology AM0010 of the Approved Methodologies for CDM activities, the carbon dioxide (CO2) emissions reduction and electricity generation capacities for three CO2 emissions intensities from flaring of methane have been estimated for 2008-2030. The total LFG generation has amounted to 319.8-2371.2 Mm³ for 1998-2030. At 50% (v/v), methane content and 60% recovery, the maximum LFG generation and recoverable volume of methane amounted to 1869.5 and 560.9 Mm³ for 2008-2030, respectively. This corresponded to an emissions reduction of up to 421,657.3tCO2e. Potential power generations have been found to vary from 44.6-937 GWhour for the three emissions intensities.

The co-composting of shredded waste office paper with Broiler Litter (BL) in windrows was analysed in this study. Two compost mixes were monitored for five weeks; Mix 1 comprised 322kg BL, 117 kg shredded paper and 310L water and Mix 2 consisted of 112 kg BL, 265 kg shredded paper and 290 L water. The initial wet moisture content, initial porosity and initial wet bulk density for Mix 1 were 54.6%, 74.7% and 337kg/m?, respectively. The respective parameters for Mix 2 were 48.6%, 87.7% and 185 kg/m?. The initial C:N ratio was kept at 20.8 in both mixes. Peak temperatures recorded for Mix 1 and Mix 2 at day 5 were 71.4?C and 62.7?C, respectively. Temperatures remained above 60?C for more than 10 days in both windrows. The pH for both mixes varied between 7.2 and 8.8. An increase in wet bulk density of 47.6% for Mix 1 and 150% for Mix 2 was obtained. The net decrease in Volatile Solids (VS) was of 57.1% (Mix 1) and 56.3% (Mix 2) at the end of week 5. The respiration rate peaked at 33.7 mg CO2.C/day.gVS on day 3 for Mix 1 and decreased to 0.98 mg CO2.C/day.gVS on day 37. The concentrations of lead, cadmium, total chromium and zinc were 612 mg/kg, 60.8 mg/kg 103.2 mg/kg and 5760 mg/kg, respectively, in the final compost of Mix 1. NPK content of the final compost from Mix 1 was 5-5-10 (dry matter basis) with a level of phosphorous of 20,817 ppm.