Degradation of gaseous volatile organic compounds (VOCs) by a novel UV-ozone technology.

In this study, a UV-assisted ozonation (UV/O3) process for the degradation of VOCs emissions with a final scrubbing phase was implemented to evaluate the removal efficiency of toluene and to prevent the release of polluting intermediates of the single-step process. Inlet toluene concentration and applied voltage were varied in order to investigate several operating conditions. The results highlighted that at higher inlet concentration the abatement of toluene was lower, while increase in ozone concentration led to an increase of the degradation efficiencies. The additional water scrubbing step enhanced the abatement of UV/O3 up to 98.5%, due to the solubilisation of ozone and by-products in the process water and, thus, the further oxidation of the contaminants within this phase. A maximum Elimination Capacity (ECmax) of 22.6 g m-3 h-1 was achieved with the UV/O3 + Scrubbing. The combined system boosted higher performance and stability compared to the stand-alone (UV/O3) process along with a more economical and environmental sustainability.

Next-generation of instrumental odour monitoring system (IOMS) for the gaseous emissions control in complex industrial plants.

Odour emissions from complex industrial plants may cause potential impacts on the surrounding areas. Consequently, the validation of effective tools for the control of the associated environmental pressures, without hindering economic growth, is strongly needed. Nowadays, senso-instrumental methods by using Instrumental Odour Emissions Systems (IOMSs) is among the most attractive tool for the continuous monitoring of environmental odours, allowing the possibility of obtaining real-time information to support the decision-making process and proactive approach. The systems complexity and scarcity of real data limited their wider full-scale employment. The study presents an advanced prototype of IOMS for the continuous classification and quantification of the odours emitted in ambient air by complex industrial plants, to continuously control the plants emissions with backwards approach. The IOMS device was designed and optimized and included the system for the automatic control of the conditions inside the measurement chamber. The designed operational procedures were presented and discussed. Results highlighted the influence of temperature and air flow rate for the measurement repeatability. Accurate prediction model was created and optimized and resulted able to distinguish 3 different industrial odour sources with accuracy approximately equal to 96%. The models were optimized thanks to the software features, which allowed to automatically apply the designed statistical procedures on the identified dataset with different pre-processing approach. The usefulness of having a fully-developed and user-friendly flexible system that allowed to select and automatically compare different settings options, including the different feature extraction methods, was demonstrated in order to identify the best prediction model.

Ultrasonic processes for the advanced remediation of contaminated sediments.

Sediments play a fundamental role in the aquatic environment, so that the presence of contaminants poses severe concern for the possible negative effects on both environmental and human health. Sediment remediation is thus necessary to reduce pollutant concentrations and several techniques have been studied so far. A novel approach for sediment remediation is the use of Advanced Oxidation Processes, which include ultrasound (US). This paper focuses on the study of the ultrasonic effects for the simultaneous reduction of both organic and inorganic contaminants from sediments. To this end, the US technology was investigated as a stand-alone treatment as well as in combination with an electro-kinetic (EK) process, known to be effective in the removal of heavy metals from soil and sediments. The US remediation resulted in higher organic compound degradation, with an average 88% removal, but promising desorption yields (47-84%) were achieved for heavy metals as well. The combined EK/US process was found to be particularly effective for lead. Experimental outcomes highlighted the potential of the ultrasonic technology for the remediation of contaminated sediments and addressed some considerations for the possible scale-up.

Control of odour emission in wastewater treatment plants by direct and undirected measurement of odour emission capacity.

Odour emissions from wastewater treatment plants (WWTPs) are considered to be the main causes of disturbance noticed by the exposed population and have relevant impacts on both tourism economy and land costs. Odour impact from WWTPs is generated by primary and secondary odour emissions. Primary odour emissions are related especially to the wastewater type and variability discharged into the sewer and directed to the WWTP, and to the wastewater collection and sewage system. Secondary odours are related to the treatment units of the plant. Several studies describe the key role of primary odour emissions and how they are strongly related to odour impacts of WWTPs. In this way, a opportune characterization of the emission capacity of primary odour could be an effective way to control odour emission in the WWTPs. In this study the odour emission capacity (OEC) of different domestic sewers was described and investigated; a correlation between the OEC and the main physical-chemical parameters of wastewater quality was also carried out. Results of this study identify the optimum conditions for sampling and measuring OEC in wastewaters and define its dependence by wastewater quality. These results can contribute to setting the standards for the maximum odourant content of wastewater that are discharged into the publicly owned sewage system.

Ultrasonic degradation, mineralization and detoxification of diclofenac in water: optimization of operating parameters.

The 20 kHz ultrasound-induced degradation of non-steroidal, anti-inflammatory drug diclofenac (DCF) was investigated. Several operating conditions, such as power density (25-100 W/L), substrate concentration (2.5-80 mg/L), initial solution pH (3.5-11), liquid bulk temperature and the type of sparging gas (air, oxygen, argon), were tested concerning their effect on DCF degradation (as assessed measuring absorbance at 276 nm) and hydroxyl radicals generation (as assessed measuring H(2)O(2) concentration). Sample mineralization (in terms of TOC and COD removal), aerobic biodegradability (as assessed by the BOD(5)/COD ratio) and ecotoxicity to Daphnia magna and Artemia salina were followed too. DCF conversion is enhanced at increased applied power densities and liquid bulk temperatures, acidic conditions and in the presence of dissolved air or oxygen. The reaction rate increases with increasing DCF concentration in the range 2.5-5mg/L but it remains constant in the range 40-80 mg/L, indicating different kinetic regimes (i.e. first and zero order, respectively). H(2)O(2) production rates in pure water are higher than those in DCF solutions, implying that decomposition basically proceeds through hydroxyl radical reactions. Mineralization is a slow process as reaction by-products are more stable than DCF to total oxidation; nonetheless, they are also more readily biodegradable. Toxicity to D. magna increases during the early stages of the reaction and then decreases progressively upon degradation of reaction by-products; nevertheless, complete toxicity elimination cannot be achieved at the conditions in question. Neither the original nor the treated DCF samples are toxic to A. salina.

Heterogenous photocatalytic degradation kinetics and detoxification of an urban wastewater treatment plant effluent contaminated with pharmaceuticals.

Degradation kinetics and mineralization of an urban wastewater treatment plant effluent contaminated with a mixture of pharmaceutical compounds composed of amoxicillin (10 mg L(-1)), carbamazepine (5 mg L(-1)) and diclofenac (2.5 mg L(-1)) by TiO(2) photocatalysis were investigated. The photocatalytic effect was investigated using both spiked distilled water and actual wastewater solutions. The process efficiency was evaluated through UV absorbance and TOC measurements. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Lepidium sativum) was performed to evaluate the potential toxicity of the oxidation intermediates. A pseudo-first order kinetic model was found to fit well the experimental data. The mineralization rate (TOC) of the wastewater contaminated with the pharmaceuticals was found to be really slow (t(1/2)=86.6 min) compared to that of the same pharmaceuticals spiked in distilled water (t(1/2)=46.5 min). The results from the toxicity tests of single pharmaceuticals, their mixture and the wastewater matrix spiked with the pharmaceuticals displayed a general accordance between the responses of the freshwater aquatic species (P. subscapitata>D. magna). In general the photocatalytic treatment did not completely reduce the toxicity under the investigated conditions (maximum catalyst loading and irradiation time 0.8 g TiO(2) L(-1) and 120 min respectively).

Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation.

The application of sonolysis (US) for remediation of wastewater is an area of increasing interest. The aim of this study was to evaluate the ultrasonic (US) process on the degradation of pharmaceuticals (diclofenac (DCF), amoxicillin (AMX), carbamazepine (CBZ)) in single solutions and also in three mixtures spiked in urban wastewater effluent. Several operating conditions, such as power density (25-100 W L(-1)), initial substrate concentrations (2.5-10 mg L(-1)), initial solution pH (3-11), and air sparging were varied for the evaluation and understanding of the process. The degradation (as assessed by measuring UV absorbance), the generation of hydroxyl radicals (as assessed measuring H(2)O(2) concentration), the mineralization (in terms of TOC and COD removal), and the aerobic biodegradability (as assessed by the BOD(5)/COD ratio) were monitored during sonication. Ecotoxicity to Daphnia magna, Pseudokirchneriella subcapitata and Lepidium sativum before and after treatment was also evaluated. It was found that the pharmaceuticals conversion is enhanced at increased applied power densities, acidic conditions and in the presence of dissolved air. The reaction rate increases with increasing initial concentration of single pharmaceuticals but it remains constant in the mixtures, indicating different kinetic regimes (i.e. first and zero order respectively). Mineralization is a slow process as reaction by-products are more stable than pharmaceuticals to total oxidation; nonetheless, they are also more readily biodegradable. The toxicity of the wastewater samples before and after contamination with pharmaceuticals both in mixtures and in single substance-containing solutions was observed more severely on P. subcapitata; a fact that raises concerns in regards to the discharge of such effluents. D. magna displayed less sensitivity compared to P. subcapitata because it belongs in a lower taxonomic species than D. magna. The germination index of L. sativum in the presence of the drugs' mixture was stimulated instead of inducing any toxicity effect and this might be attributed to the fact the sample, laden with very low drug concentrations was able to act as a provider of additional nutrient elements.

Instrumental characterization of odour: a combination of olfactory and analytical methods.

Odour emissions are a major environmental issue in wastewater treatment plants and are considered to be the main cause of disturbance noticed by the exposed population. Odour measurement is carried out using analytical or sensorial methods. Sensorial analysis, being assigned to the "human sensor", is the cause of a considerable uncertainty. In this study a correlation between analytical and sensorial methods was investigated. A novel tool was used to both define odour indexes and characterise the odour sources and the volatile substances that cause annoyance in a wastewater treatment plant, with the aim to remove the subjective component in the measure of the odours and define the induced impact. The sources and the main chemical substances responsible for the olfactory annoyances were identified. Around 36 different substances were detected, with more than half being smell relevant components as well as responsible. Dimethyl disulphide was identified as key compound. Results highlight the applicability of highly correlation between analytical and sensorial methods in odour emission monitoring.

Wastewater disinfection by combination of ultrasound and ultraviolet irradiation.

Reclamation and reuse of wastewater is one of the most effective ways to alleviate water resource scarcity. In many countries very stringent limit for chlorination by-products such as trihalomethanes has been set for wastewater reuse. Accordingly, the use of alternative oxidation/disinfection systems should be evaluated as possible alternative to chlorine. Recently ultrasound (US) was found to be effective as pre-treatment for wastewater disinfection by UV irradiation. The aim of this work is to investigate the wastewater advanced treatment by simultaneous combination of UV and US in terms of bacteria inactivation (Total coliform and Escherichia coli) at pilot-scale. The pilot plant was composed of two reactors: US-UV reactor and UV reactor. The influence of different reaction times, respective US and UV dose and synergistic effect was tested and discussed for two different kinds of municipal wastewater. An important enhancement of UV disinfection ability has been observed in presence of US, especially with wastewater characterized by low transmittance. In particular the inactivation was greater for T. coliform than for E. coli. Furthermore, the results obtained showed also that the fouling formation on the lamps was slower in US-UV reactor than in UV reactor both with and without solar radiation.

Degradation of diclofenac by TiO(2) photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays.

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO(2) photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5-80mgL(-1)) and photocatalyst loadings (0.2-1.6gTiO(2)L(-1)) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80mgL(-1)) and at 1.6gTiO(2)L(-1) photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate.

Odour monitoring of small wastewater treatment plant located in sensitive environment.

Small wastewater treatment plants are often localized nearby tourist areas. Odour emissions are a major environmental issue in these plants and are considered to be the main cause of disturbance noticed by the exposed population. Odour measurement is carried out using analytical or sensorial methods. Sensorial analysis, being assigned to the "human sensor", is the cause of a considerable uncertainty.In this study, a novel procedure based on highly innovative analytical tool was used to identify and characterise the odour sources and the volatile substances that cause annoyance in a SWWTP located in a sensitive area, with the aim to remove the subjective component in the measure of the odours and define the induced impact. At the same time key odour compounds are detected, and the relationship between their concentration and the performances of the plant are investigated.The sources and the main chemical substances responsible for the olfactory annoyances were identified. Results highlight the applicability of the highly innovative tool in odour emission monitoring. Around 39 different substances were detected, with almost half being smell relevant components as well as responsible. Dimethyl disulphide was identified as key compound connected to the efficiency of the process.

Wastewater toxicity of tannin- versus chromium-based leather tanneries in Marrakesh, Morocco.

The toxicity of leather tanning wastewater from a traditional tannery (TT), which is based on vegetable tannin (VT), was compared with wastewater from a tannery combining the use of chromium-based tanning (CT) with VT-based tanning operations. Wastewater samples from a TT and a CT plant as well as from five sewer sampling points were collected in Marrakesh, Morocco, and the concentrations of VT and some selected inorganics were measured. A set of bioassays were used to test wastewater toxicity in sea urchin (Paracentrotus lividus) embryos and sperm, in Daphnia magna, and in marine microalgae (Dunaliella tertiolecta). Toxicity end points included: (1) developmental defects, embryonic mortality, sperm fertilization success, and offspring damage in sea urchins; (2) D. magna immobilization; and (3) algal growth rate inhibition. Toxicity tests on TT and CT effluents (TTE and CTE) were run at dilutions ranging from 0.1% to 2% (sea urchins and algae) or up to 12% in D. magna. Parallel bioassays were run on VT extract (VTE) at nominal tannin concentrations ranging from 0.1 to 10 mg l(-1). The results showed higher toxicity of CTE compared with TTE. CTE toxicity in sea urchins and algae showed concentration-related trends, whereas TTE exerted hormetic effects at levels of 0.1% to 0.2% and toxic effects at levels >or=1%. The same trends were observed for VTE, suggesting a prevailing role of tannin in TTE-associated effects. The moderate wastewater toxicity of VT-based tanneries might prompt interest in the VT tanning process.

Fenton and photo-Fenton treatment of a synthetic tannin used in leather tannery: a multi-approach study.

The aim of this work was to compare the behaviour of Fenton and photo-Fenton (UV-A, UV-C) processes to treat synthetic tannin (syntan) used in leather tannery which is one of the most polluting industries, releasing many xenobiotics. Both oxidation processes were performed at pH 3.0 and temperature 40-45 degrees C, which is the original temperature of the re-tanning process, in synthetic solutions containing 100 and 300 mg/L of COD equivalent of syntan. The efficiency of the applied oxidation processes was monitored by chemical oxygen demand (COD), oxidation redox potential (ORP) and aromaticity (UV280) and double bond (UV254) absorbance measurements. Acute toxicity test on Daphnia magna was performed to monitor toxicity in untreated and treated syntan solution. Gas chromatography-mass spectrometry (GC-MS) was applied to identify by-products of partial oxidation occurring in treated samples. The effective ratio of H2O2/FeSO4 for photo-Fenton processes was found to be feasible in terms of reagents used in the process.

Tertiary filtration in small wastewater treatment plants.

Tertiary filtration can be proposed in small wastewater treatment plants with impact on protected water bodies. Rotating disk filters may be adopted, in respect to conventional sand filters, when low availability of space and low investment costs are the prevailing conditions. The overall objective of this research was to evaluate the filtration efficiency of rotating disk filters; to compare effectiveness with traditional sand filters; to analyse thoroughly the importance of particle size distribution in wastewater tertiary filtration. In the experimental activity, conventional wastewater quality parameters were investigated and particle size distribution (PSD) was characterized to discuss the filter effectiveness. The effect of design and operation parameters of tertiary filters were discussed related to particle removal curves derived from particles counts. Analysis of particle size distribution can be very useful to help comprehension of filtration processes, design of filtration treatments and to decide the best measures to improve filter performance.

Groundwater recharge in an endoreic basin with reclaimed municipal wastewater.

The aim of this paper was to evaluate the groundwater pollution in an endoreic basin in southern Italy. The aquifer circulation was carried out on two different levels: a shallow groundwater, with a water table of about 10 m, and a deep groundwater in a karst aquifer, with a water table of 140-190 m. Reclaimed municipal wastewater and superficial water collected in the catchment area were both drained in a swallow hole linked with the deep groundwater. The agricultural practice conducted in the endoreic basin produced an excess of nitrate in the soil. Nitrate was subsequently washed out and displaced in the groundwater. With regard to the EU Drinking Water Directive (98/83/EC), the research activity conducted during 2003 showed the absence of pollution in the deep groundwater used for drinking water supply. The shallow groundwater, instead, was strongly influenced by agricultural and pasture activities, with detectable levels of nitrates and bacteria. In order to reduce the load of pollution entering the swallow hole and then in the deep groundwater, the realisation of a constructed wetland plant was proposed to improve the quality of reclaimed wastewater, as well as to pursue the wastewater reuse in agriculture.

Treatment of high strength wastewater with vertical flow constructed wetland filters.

The aim of the present study was to evaluate the behaviour of vertical flow constructed wetlands to treat high strength wastewater. Influents were obtained mixing tap water with different percentages of MSW landfill leachate (5%, 10% and 20%). Phragmites australis seedlings were used as macrophytes. The reeds were nurtured during three spring months, before the start of the experimental period. Three and four days of detention time were adopted. Influent concentrations of 510-2,050 mg L(-1), 180-740 mg L(-1) and 65-260 mg L(-1) were obtained for COD, N-NH4(+) and N-NO3(-), respectively. The environmental temperature averaged around 31.0 +/- 1.4 degrees C. During the experimental period, all parameters showed an increasing removal efficiency trend. Best results in terms of COD removal were obtained for mixtures at lowest rate of landfill leachate; while, denitrification process showed an opposite behaviour; finally, the removal of ammonia nitrogen appeared to be independent upon influent concentrations. Analysis carried out on the reed tissues showed a theoretic maximum storage of TKN in the leaves of about 55 mg/g dry weight. A leachate percentage of about 35% was derived to be able to fully inhibit the growth of macrophytes.

Energy from gasification of solid wastes.

Gasification technology is by no means new: in the 1850s, most of the city of London was illuminated by "town gas" produced from the gasification of coal. Nowadays, gasification is the main technology for biomass conversion to energy and an attractive alternative for the thermal treatment of solid waste. The number of different uses of gas shows the flexibility of gasification and therefore allows it to be integrated with several industrial processes, as well as power generation systems. The use of a waste-biomass energy production system in a rural community is very interesting too. This paper describes the current state of gasification technology, energy recovery systems, pre-treatments and prospective in syngas use with particular attention to the different process cycles and environmental impacts of solid wastes gasification.