Unravelling the performance of UV/H2O2 on the removal of pharmaceuticals in real industrial, hospital, grey and urban wastewaters.

This study provides an integrated assessment of UV/H2O2 treatment of different real wastewater matrices: two urban wastewater treatment plants (WWTPs) secondary effluents, greywater, hospital, and pharmaceutical industrial effluents. It considers micropollutant removal (up to 30 pharmaceuticals and 13 transformation products at environmental concentrations), energy efficiency and effluent toxicity. The complexity of the wastewater matrix negatively affected the UV fluence in the photo-reactor, scavenged hydroxyl radicals and hindered a proper H2O2 utilization thus reducing the treatment efficiency. At the optimal treatment conditions, overall pharmaceuticals removal was the highest for urban WWTPs effluents (69%-86%), followed by greywater (59%), hospital (36%) and industrial (17%) effluents. The ecotoxicity of the treated samples was reduced around one toxicity unit after the UV/H2O2 treatment in all cases except in industrial wastewater. The average observed removal in urban wastewater effluents and greywater for photo-susceptible, moderately photo-susceptible, and most photo-resistant compounds was 93%, 73% and 46% including outliers, respectively. The calculated electrical energy per order (EEO) values were 0.9-1.5 kWh/(m3·order) for urban WWTP effluents and greywater while for hospital and industrial effluents was much higher (7.3-9.1 kWh/(m3·order)).

The use of organic wastes at different degrees of maturity as carbon sources for denitrification of landfill leachate.

In this study different garden refuses were investigated to ascertain their efficiency to act as carbon sources in a denitrification system. Six different garden refuse materials were studied: commercial and domestic garden refuse raw (CGR RAW, DGR RAW), immaturely composted domestic and commercial garden refuse (DGR 10 and CGR 10 respectively), commercial garden refuse composted by Dome Aeration Technology and by "turned windrow" technology (DAT and TW). Different concentrations of synthetic nitrate solution were used to assess the efficiency of each substrate. The results demonstrate that all substrates were able to sustain the denitrification process. However, due to its higher C/N ratio the CGR RAW was the better performing of the materials, reaching 100% removal after 8 and 12h for the 100 and 500 mg L(-1) respectively and after 11 days for 2000 mg L(-1). Kinetic studies revealed that the zero-order reaction better describes the process indicating a denitrification rate independent from the nitrate concentrations investigated when 100 and 500 mg L(-1) of nitrate were used. The study demonstrated the suitability of organic municipal solid wastes to sustain denitrification, opening a new scenario towards a low cost and in situ solution for treatment of landfill leachate by using wastes, otherwise disposed of in landfill.

Biotreatment of Cr(VI) contaminated waters by sulphate reducing bacteria fed with ethanol.

Biological treatment of Cr(VI) contaminated waters was performed in fixed bed reactors inoculated with SRB (sulphate-reducing bacteria) growing on ethanol. Treatment efficiency was evaluated by checking chemical abatement of Cr(VI) and by ecotoxicological tests using the nematode Caenorhabditis elegans. A preliminary comparison between ethanol and lactate was performed, denoting that using ethanol, the same values of final sulphate abatement were obtained. In addition ethanol showed to be a substrate more competitive than lactate in kinetic terms. Fixed bed column reactors were continuously fed with a solution containing sulphates (3 g L(-1)), ethanol (1.5 g L(-1)) and Cr(VI) (50 mg L(-1)). At steady state the column inoculated with SRB removed 65 ± 5% of sulphate and 95 ± 5% of chromium. Bioactive removal mechanisms predominated over biosorption. Diminution of Cr(VI) toxicity was assessed by using the nematode C. elegans as a test organism showing that the survival of nematodes was 20% in the presence of the untreated influent and raised up to 53% when the nematodes were exposed to the treated effluent.

Biotreatment and bioassessment of heavy metal removal by sulphate reducing bacteria in fixed bed reactors.

In this work a batch-optimised mixture (w/w %: 6% leaves, 9% compost, 3% Fe(0), 30% silica sand, 30% perlite, 22% limestone) was investigated in a continuous fixed bed column reactor for the treatment of synthetic acid-mine drainage (AMD). A column reactor was inoculated with sulphate-reducing bacteria and fed with a solution containing sulphate and heavy metals (As(V), Cd, Cr(VI), Cu and Zn). At steady state, sulphate abatement was 50+/-10%, while metals were totally removed. A degradation rate constant (k) of 0.015+/-0.001h(-1) for sulphate removal was determined from column data by assuming a first order degradation rate. Reduction of AMD toxicity was assessed by using the nematode Caenorhabditis elegans as a test organism. A lethality assay was performed with the toxicants before and after the treatment, showing that only 5% of the animals were still alive after 48h in presence of the contaminants, while the percentage increased to 73% when the nematodes were exposed to the solution eluted from the column.