Roberta Pedrazzani

The influence of different disinfectants on mutagenicity and toxicity of urban wastewater

Many human pathogenic micro-organisms can be transmitted by waters contaminated by wastewater effluents. Wastewater disinfection helps prevent the spread of these pathogens in aquatic environments. Chlorination is the most widely used method for the disinfection of wastewater, but can cause the formation of mutagenic/carcinogenic and toxic by-products which are potentially harmful to human and aquatic organisms. The aim of this research was to study the influence of disinfectants alternative to chlorine, such as chlorine dioxide, ozone, peracetic acid and UV radiation, on the formation of mutagenic and toxic compounds in wastewater. Wastewater samples were collected before and after disinfection in summer and in winter and then adsorbed using silica C18 cartridges. Concentrates were tested for mutagenicity using the Ames test. For toxicity test, a bioluminescence assay using Vibrio fischeri photobacteria was employed. To detect DNA damage activity non-concentrated water samples were tested using two genotoxicity plant tests (Allium test and Tradescantia/micronuclei test). All disinfectant treatments produced bacterial mutagenicity, particularly after treatment with ClO2 or ozone. The Allium cepa test gave positive results only for PAA-treated wastewater sampled in winter and the Tradescantia/MCN test always gave negative results. Raw wastewater, ClO2- and PAA-disinfected waters showed toxic effects in the marine bacteria test.

Effect of biological and chemical oxidation on the removal of estrogenic compounds (NP and BPA) from wastewater: An integrated assessment procedure

A major source of the wide presence of EDCs (Endocrine Disrupting Compounds) in water bodies is represented by direct/indirect discharge of sewage. Recent scientific literature reports data about their trace concentration in water, sediments and aquatic organisms, as well as removal efficiencies of different wastewater treatment schemes. Despite the availability of a huge amount of data, some doubts still persist due to the difficulty in evaluating synergistic effects of trace pollutants in complex matrices. In this paper, an integrated assessment procedure was used, based on chemical and biological analyses, in order to compare the performance of two full scale biological wastewater treatment plants (either equipped with conventional settling tanks or with an ultrafiltration membrane unit) and tertiary ozonation (pilot scale). Nonylphenol and bisphenol A were chosen as model EDCs, together with the parent compounds mono- and di-ethoxylated nonylphenol (quantified by means of GC-MS). Water estrogenic activity was evaluated by applying the human breast cancer MCF-7 based reporter gene assay. Process parameters (e.g., sludge age, temperature) and conventional pollutants (e.g., COD, suspended solids) were also measured during monitoring campaigns. Conventional activated sludge achieved satisfactory removal of both analytes and estrogenicity. A further reduction of biological activity was exerted by MBR (Membrane Biological Reactor) as well as ozonation; the latter contributed also to decrease EDC concentrations.

Licit and illicit drugs in a wastewater treatment plant in Verona, Italy.

The occurrence of 12 active substances among licit and illicit drugs was investigated over a 2 week period inflowing and outflowing in an activated sludge wastewater treatment plant in the city of Verona, Northern Italy. Chemical analyses were performed by means of on-line solid phase extraction coupled to high performance liquid chromatography-tandem mass spectrometry in order to minimize sample pre-treatment. Quantifiable concentrations, up to hundreds of ng/L, were detected in influent and in effluent only for carbamazepine, codeine and benzoylecgonine. Such values are in accordance with literature data, so as removal efficiencies: it was observed that there was pretty much no abatement for carbamazepine, while average removal percentages of about 60% and 90% were calculated for codeine and benzoylecgonine, respectively. These results provide useful information (also concerning some active principles never or rarely detected, up to now, such as lormetazepam) for integrated water cycle managing, also taking into account the specific characteristics of the receiving water basin.

EDCs, estrogenicity and genotoxicity reduction in a mixed (domestic + textile) secondary effluent by means of ozonation: A full-scale experience

WWTP (wastewater treatment plant) effluents are considered to be a major source for the release in the aquatic environment of EDCs (Endocrine-Disrupting Compounds), a group of anthropogenic substances able to alter the normal function of the endocrine system. The application of conventional processes (e.g. activated sludge with biological nitrogen removal) does not provide complete elimination of all these micropollutants and, consequently, an advanced treatment should be implemented. This experimental work was conducted on the tertiary ozonation stage of a 140,000 p.e. activated sludge WWTP, treating a mixed domestic and textile wastewater: an integrated monitoring, including both chemical (nonylphenol, together with the parent compounds mono- and di-ethoxylated, and bisphenol A were chosen as model EDCs) and biological (estrogenic and genotoxic activities) analyses, was carried out. Removal efficiencies of measured EDCs varied from 20% to 70%, depending on flow conditions (ozone dosage being 0.5 gO3/gTOC). Biological tests, furthermore, displayed that the oxidation stage did not significantly reduce (only by 20%) the estrogenicity of the effluent and revealed the presence and/or formation of genotoxic compounds. These results highlight the importance of the application of an integrated (biological+chemical) analytical procedure for a global evaluation of treatment suitability; poor performances recorded in this study have been attributed to the presence of a significant industrial component in the influent wastewater.

Biodegradability, toxicity and mutagenicity of detergents: Integrated experimental evaluations.

The widespread use of detergents has raised concern with regard to the environmental pollution caused by their active ingredients, which are biorefractory, toxic and persistent. Since detergents are complex mixtures of different substances, in which synergistic effects may occur, we aimed to assess the mutagenicity of different detergent formulations, taking into account aquatic toxicity and ready biodegradability. We performed a ready biodegradability test (OECD 301 F), Daphnia magna and Vibrio fischeri toxicity tests, and mutagenicity tests (Salmonella/microsome test, Allium cepa test and comet assay). Six detergent formulations were examined, 3 pre-manufacture and 3 commercially available. All detergents presented ready biodegradability. EC50 values varied for all products, according to the marker organism used, but were always higher than the more stringent value considered for aquatic toxicity assessment (V. fischeri 10-60 mg/L; D. magna 25-300 mg/L; A. cepa 250-2000 mg/L). None of the detergents caused mutations in bacteria. However, one commercial ecolabelled product induced an increase in micronucleus frequency in A. cepa root cells. All pre-manufacture detergents and one commercial one, which gave negative results in the Ames and A. cepa tests, induced DNA damage in human leukocytes. A more accurate evaluation of the environmental impact of complex mixtures such as detergents requires a battery of tests to describe degradation, as well as toxicological and mutagenic features.

Integration between chemical oxidation and membrane thermophilic biological process

Full scale applications of activated sludge thermophilic aerobic process for treatment of liquid wastes are rare. This experimental work was carried out at a facility, where a thermophilic reactor (1,000 m(3) volume) is operated. In order to improve the global performance of the plant, it was decided to upgrade it, by means of two membrane filtration units (ultrafiltration -UF-, in place of the final sedimentation, and nanofiltration -NF-). Subsequently, the integration with chemical oxidation (O(3) and H(2)O(2)/UV processes) was taken into consideration. Studied solutions dealt with oxidation of both the NF effluents (permeate and concentrate). Based on experimental results and economic evaluation, an algorithm was proposed for defining limits of convenience of this process.

How green are environmental technologies? A new approach for a global evaluation: The case of WWTP effluents ozonation

The research on the impact of chemical pollution is now increasingly attracted by the topic of organic micropollutants: as secondary biological treatment of wastewater does not provide the complete elimination of these substances, an advanced treatment downstream the biological process can be implemented. Notwithstanding, the benefits of improved effluent quality can be weakened by the negative effects on air quality, when energy consumption and related pollutants emissions deriving from the advanced treatment technologies are taken into account. It is the aim of this work to present an innovative methodology to judge the environmental compatibility of wastewater treatment processes on the basis of the damage on human health produced/avoided, expressed as an economic value. In particular, while for air pollution the established external costs were applied, for water pollution the rates of the impacts on human health have been evaluated in terms of Global Burden of Disease and measured in units of DALY (Disability-Adjusted Life Years), then converted into costs based on Gross Domestic Product. As a first application, this procedure was used for assessing environmental compatibility of a final ozonation: the results of this study showed that the reduction of water pollution achieved by means of ozonation might be beneficial for human health at an extent which is in the same order of magnitude of damage caused by air pollution, emphasizing that the question if the use of advanced (energy-intensive) treatments is a proper solution to remove organic micropollutants from wastewater remains still open.

Removal of endocrine disrupting compounds from wastewater treatment plant effluents by means of advanced oxidation.

Municipal sewage and WWTP effluents are considered to be a major source of pollution, regarding the occurrence of endocrine disrupting compounds (EDCs) in the environment. Although removal potential of many EDCs by conventional WWTPs is recognised, literature data are not easily comparable. Besides, in order to reach very low concentrations, a further treatment might be sometimes required. Positive results can be achieved by tertiary chemical oxidation; nevertheless, technical-economic suitability is still to be fully demonstrated. In this work, two estrogen-like susbstances were considered: nonylphenol (NP) (and its parent compounds) and bisphenol A (BPA). The experimental work was conducted at Verona (Northern Italy) WWTP (370,000 p.e.): after a 15 days sampling campaign, which was carried out in order to calculate mass balance of target compounds, chemical oxidation tests were performed on effluent by means of UV/H(2)O(2) process and ozonation. Technical-economic feasibility of these solutions is discussed.

Is anaerobic digestion effective for the removal of organic micropollutants and biological activities from sewage sludge

The occurrence of emerging organic micropollutants (OMPs) in sewage sludge has been widely reported; nevertheless, their fate during sludge treatment remains unclear. The objective of this work was to study the fate of OMPs during mesophilic and thermophilic anaerobic digestion (AD), the most common processes used for sludge stabilization, by using raw sewage sludge without spiking OMPs. Moreover, the results of analytical chemistry were complemented with biological assays in order to verify the possible adverse effects (estrogenic and genotoxic) on the environment and human health in view of an agricultural (re)use of digested sludge. Musk fragrances (AHTN, HHCB), ibuprofen (IBP) and triclosan (TCS) were the most abundant compounds detected in sewage sludge. In general, the efficiency of the AD process was not dependent on operational parameters but compound-specific: some OMPs were highly biotransformed (e.g. sulfamethoxazole and naproxen), while others were only slightly affected (e.g. IBP and TCS) or even unaltered (e.g. AHTN and HHCB). The MCF-7 assay evidenced that estrogenicity removal was driven by temperature. The Ames test did not show point mutation in Salmonella typhimurium while the Comet test exhibited a genotoxic effect on human leukocytes attenuated by AD. This study highlights the importance of combining chemical analysis and biological activities in order to establish appropriate operational strategies for a safer disposal of sewage sludge. Actually, it was demonstrated that temperature has an insignificant effect on the disappearance of the parent compounds while it is crucial to decrease estrogenicity.

The assessment of WWTP performance: Towards a jigsaw puzzle evaluation?

A chemical and bio-analytical protocol is proposed as a holistic monitoring framework for the assessment of WWTPs (Wastewater Treatment Plants) performance. This combination of tests consists of: i) an analysis of emerging contaminants, to be added to the established physico-chemical parameters in order to understand the causes of (new) pollution phenomena and ii) some of the bio-analytical tools most widely applied in the field of wastewater research, which provide information on groups of chemicals with a common mode of toxic action (baseline toxicity, estrogenicity and mutagenicity/genotoxicity, selected as the most representative for human health). The negative effects of the discharge can thus be highlighted directly and used to assess the global environmental impact of WWTPs. As a validation, this multi-tiered approach was applied to a full-scale WWTP (150,000 p.e.), where different measurements were carried out: EDCs (Endocrine Disrupting Compounds) detection; algal growth inhibition, bioluminescence inhibition and acute toxicity test (for baseline toxicity); an E-Screen-like assay (for estrogenic activity); Ames, Allium cepa and Comet tests (for mutagenic/genotoxic activity). As a result, the WWTP showed good performance for all these issues, displaying its ability to enhance effluent quality, except for residual mutagenic behaviour, probably due to the by-products generated by the tertiary ozonation.