Degradation of aqueous solution of bisphenol A (BPA) has been investigated through non-catalytic and catalytic ozonation treatments conducted in a semi-batch reactor. Non-catalytic ozonation resulted in complete degradation of aqueous BPA in less than 3 min but did not completely convert the reaction intermediates of BPA ozonation into CO2 and H2O. The main goal of this study was to find an effective heterogeneous catalyst to increase the extent of BPA mineralization at different pH conditions. In this way, the most promising catalyst carrier was γ-Al2O3; at pH = 8.0, 68 % of total organic carbon (TOC) was removed in the period of 75 min, out of which 42 % was attributed to mineralization. Finally, 3.0 wt.% Ru/γ-Al2O3 catalyst exhibited over 82 % of TOC removal after 240 min of ozonation at pH = 5.9, of which 56 % was mineralized.

The proficiency testing of wastewater sampling is organized by the Laboratory for Environmental Sciences and Engineering at the National Institute of Chemistry, Slovenia (NIC). Preliminary tests started in 2010 at two candidate sites to choose for a trial the most convenient one. In 2012, we organized the first collaborative field trial on wastewater sampling and such trials continued in 2013 and 2014. Between 16 and 20 sampling teams were selected from those that (1) participate in the national wastewater monitoring program and (2) perform analytical activities in laboratories. The participants used a 6-h time proportional sampling approach. They used sampling equipment with different principles of sample collection which take a series of discrete samples at fixed time intervals. Subsequent analyses involved both field and laboratory measurements. The participants, with only one exception, exhibited required technical skills for measuring field parameters (temperature and pH value). All samples taken were also analyzed at NIC. The variability between reported values of participants in the trials, expressed as CV , was found to be 8.5 %, 11.1 % and 9.5 % for chemical oxygen demand. Of all parameters, the largest variability was found for total organic carbon concentration amounting to 23.7 % and 35.7 %. Particular attention was given to separate the measurement uncertainty contributions arising from sampling and chemical analyses.

In this contribution, a compact reactor system is presented that enables efficient processing of grey water in order to facilitate its reutilization for flushing toilet bowls. The treatment of collected grey water is performed in combination with an aerobic/anoxic biological process carried out in a submersed bioreactor with immobilized biomass for the removal of dissolved organic substances, and a procedure of adjusting the concentration of microorganisms in the liquid phase by using a simple technique of flow-through ultraviolet-light based disinfection. In this system which operates at ambient temperature as a semi-continuous recycle reactor, significant removal of organic matter was achieved (conversions up to 65%, expressed as total organic carbon) without the occurrence of malodour. A low concentration of dispersed microorganisms was measured in treated grey water; importantly, no coliforms were accumulated in the unit.

This case study gives practical guidance on how uncertainty in monitoring programs can be reduced in wastewater sampling. Seventeen sampling teams took part in a trial. The monitoring consisted of both field and laboratory measurements. The variabilities between reported results of participants in the trial, expressed as coefficients of variation (CVs), were found to be 8.5% for chemical oxygen demand (COD), 9.5% for total suspended solids (TSS) and 14.5% for sulfate ion, respectively. (C) 2013 Elsevier Ltd. All rights reserved.

Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H 2 O 2 to reactive hydroxyls and, unlike manganese in Mn 3 O 4 or Mn 2 O 3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H 2 O 2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.

The aim of our work was to compare Fenton's oxidation with existing biological SBR (sequencing batch reactor) reactor employed for treatment of the leachate, generated in local municipal landfill (35,000 inhabitants). Efficiencies of both procedures were monitored by chemical analyses and by acute toxicity studies with Vibrio fischeri and measurement of inhibition of oxygen consumption by activated sludge. Leachate was very toxic to V. fischeri and activated sludge and toxicity was not significantly reduced as well as effluent limits were not met during treatment in existing biological treatment plant. Fenton's oxidation, accomplished at different molar ratios of reagents (M(Fe2+)/M(H2O2) was 1/1; 1/3.3; 1/6.6 and 1/13.3) and various temperatures (20–45°C), assured good removal of organic compounds (80% as COD) as well as other pollutants and slightly reduced toxicity, but effluent limits were not always met. Furthermore, additional oxidation experiments with biologically treated leachate confirmed, that Fenton's oxidation is not appropriate for polishing already treated leachate in SBR, because it degraded persistent organics into more biodegradable, still toxic ones, which could affect oxygen regime in a receiving stream. Fenton's process could not replace SBR treatment plant, but it could be a viable option for pretreatment of landfill leachate.

Our work was focused on investigation of different treatment procedures for the removal of toxic fractions from a landfill leachate, because sometimes the existing treatment in biological sequencing batch reactor (SBR) is not efficient enough, leading to a hazardous environmental impact of the present persistent and toxic compounds. The efficiency of the procedures used was monitored by chemical analyses and two toxicity tests (activated sludge and Vibrio fischeri). The existing SBR (HRT=1.9 days) removed 46–78% of COD and 96–73% of NH4+-N. Experiments were conducted with three landfill leachate samples expressing significant difference in concentrations of pollutants and with low BOD5/COD ratio (0.06/0.01/0.03). The applied methods were air stripping, adsorption to activated carbon and zeolite clinoptilolite and Fenton oxidation. Air stripping at pH 11 was a viable treatment option for the removal of ammonia nitrogen (up to 94%) and reduction of toxicity to microorganisms. In the adsorption experiments in batch system with different concentration of PAC the most effective was the highest addition (50.0gL−1) where 63–92% of COD was removed followed by significant reduction in toxicity to V. fischeri. In the column experiments with clinoptilolite 45/93/100% of NH4+-N as well as 25/32/39% of COD removal was attained. The removal efficiency for metals followed the sequence Cr>Zn>Cd>Ni. The procedure with zeolite was the second most efficient one regarding reduction of toxicity to both organisms. Fenton oxidation at molar ratio Fe2+:H2O2=1.0:10.0 assured 70–85% removal of COD but it only slightly reduced the toxicity.

Proficiency testing as a means of external quality assessment plays the role of independent evidence of laboratories’ performance. To enable laboratories to fulfil the requirements stated in legislation, methodology for evaluation of laboratories’ performance in proficiency testing schemes should incorporate principles of measurement results which are fit for intended use and incorporate evaluation of laboratories’ performances based on independent reference value. A proficiency testing scheme was designed to support Drinking Water Directive (98/83/EC) specifically. The methodology for performance evaluation, which takes into account a “fitness for purpose”-based standard deviation for proficiency assessment, is proposed and discussed in terms of requirements of the Drinking Water Directive. A ζ′ -score, modified by application of target uncertainty was developed in a way that fulfils requirements defined in the legislation. As an illustration, results are reported for nitrate concentration in water. The approach presented can also be applied to other fields of measurements.

One of the most internationally used bioassays for toxicity screening of chemicals and for toxicity monitoring of effluents and contaminated waters is the acute toxicity test with daphnid crustaceans, and in particular that performed with Daphnia magna.Standard methods have been developed for this assay that were gradually endorsed by national and international organisations dealing with toxicity testing procedures, in view of its application within a regulatory framework. As for all toxicity tests, the organisms used for the acute D. magna assay have to be obtained from live stocks which are cultured in the laboratory on live food (micro-algae).Unsurprisingly the various standard protocols of this particular assay differ - at least to a certain extent - with regard to the test organism culturing conditions. In addition, some technical aspects of the toxicity test such as the effect criterion (mortality of immobility), the exposure time, the type of dilution water, etc., also vary from one standard to another. Although this particular assay is currently used in many countries, the technical and biological problems inherent in year-round culturing and availability of the biological material and the culturing/maintenance costs of live stocks restrict its application to a limited number of highly specialised laboratories.This fundamental bottleneck in toxicity testing triggered investigations which brought forward the concept of "microbiotests" or "small-scale" toxicity tests.

The objective of this investigation was determination of feasibility of ozonation for treatment of leachates from municipal landfill. Efficiency of ozonation was determined for two leachates, different in age, composition and toxicity. We have studied the impact of ozonation time on removal of organics. The efficiency of treatment was monitored by COD, BOD5 and DOC analyses, removal of nitrogen compounds, as well as changes in toxicity. Therefore, acute toxicity tests with luminiscent bacteria Vibrio fischeri, Daphnia magna and nitrifying organisms of activated sludge (ammonium oxidation) were performed prior and after ozonation experiments. It has been confirmed that longer time of ozonation does not bring significantly better results regarding treatment of young leachate (36% in 20 minutes, 42% in 120 minutes). Two steps kinetics observed resulted in minor detoxification regarding luminiscent bacteria and no changes in effects to daphnids. More effective was ozonation of the stabilized leachate. Removal of COD reached 50% in 80 minutes and 65% in 120 minutes. Detoxification was also observed. Presented research confirmed, that ozonation itself was not effective treatment methods for investigated types of leachates for reduction of their hazardous impacts to meet regulatory effluent limits.

The European Union Water Framework Directive (EU WFD) requires the identification of significant human pressures and impacts on water bodies. An important component in protecting the ecological quality of watercourses is the regulation of point sources of pollution. The purpose of this study is to determine the harmful effects of a point source of pollution on a small river and to assess their significance for distant aquatic systems and the receiving stream. The water quality of the Ljubljanica River (Slovenia) is described in terms of point sources (tannery and municipal effluents) and diffuse sources of pollution. Tannery wastewater is a complex mixture of biogenic matter from hides and a large variety of organic chemicals added during the tanning process. The municipal effluent contained higher amounts of organic pollutants and nutrients. The harmful substances from the effluents are traced in the receiving stream and sediments. Point sources of pollution dominate at the critical ecological low flow periods of high biological activity. The water quality is marked by several determinants diluting with increasing flow and, in many cases, they link to point source pollution (organic pollution, ammonia, Cr, sulphate, and chloride), whereas nitrate shows a mixed response of point and diffuse inputs possibly mediated with in-stream loss during the growing season.

Landfilling is one of the most widely used methods for the disposal of municipal solid wastes. The degradation of the organic fraction of the wastes in combination with percolating rainwater leads to the generation of highly contaminated liquid, called leachate. Municipal landfill leachates typically contain high concentrations of inorganic compounds (ammonium and metals), as well as high levels of organics, many of them also toxic and resistant to biodegradation. Because of this, treatment efficiency of conventional biological plant for landfill leachates is usually very low. The purpose of our research work was to evaluate the quality of the leachate originating from municipal landfill and to assess efficiency of air stripping and adsorption to activated carbon for reduction of toxicity of the leachate. Both TRE procedures were used to identify the contribution of organic substances (air stripping, adsorption) and ammonium nitrogen (air stripping) to toxicity of the effluent. We have followed the efficiency of single toxicity reduction method with measurement of physicochemical parameters and toxicity bioassays. They were carried out by applying an acute toxicity test with luminiscent bacteria Vibrio fischeri and an acute test with nitrifying microorganisms from activated sludge.We have compared physico-chemical analysis and toxicity of the leachate before and after TRE procedures. Air stripping removed 85% of ammonium nitrogen at pH value of 11, but the removal of organics was low. On the other hand, adsorption to activated carbon (50 g.L-1) removed 79% of organic compounds, but ammonium nitrogen remained. Both methods (TRE) did not decrease toxicity to the nitrifying microorganisms. We have concluded that ammonium nitrogen and organic substances do not contribute much to the toxicity of the leachate. Further work will be focused on some other TRE methods, mainly ion exchange to assess the contribution of high concentrations of inorganic compounds.

In order to verify the quality of biological measurements, the National Institute of Chemistry in Slovenia is regularly organizing interlaboratory comparisons to estimate the analytical precision of different laboratories using the same test and to determine if statistically significant differences exist between results. Several interlaboratory trials named “ILC-Waste Water” (ILC-WW) were organized in the last 7 years. Acute toxicity testing with Daphnia magna mobility inhibition assay (ISO 6341) was included in eight successive rounds and about 20 laboratories from Slovenia and a few adjacent countries took part in each study with two samples (T1 and T2) at two different concentration levels. Variation coefficients of the mean 24 h EC50s were determined for each exercise and the evaluation of the interlaboratory variability was analysed. Comparisons were also made of the results and the variability laboratories using organisms taken from laboratory cultures versus those who used daphnias hatched from dormant eggs (Daphtoxkits).

Effluents may contain hazardous chemicals, which could have adverse effects on aquatic ecosystems. Important intrinsic properties are toxicity and biodegradability of effluents and they should be assessed in order to protect the aquatic environment. Microorganisms of activated sludge are responsible for biological waste water treatment. The lack of treatment effectiveness could, in case of unexpected toxic influents to waste water treatment plants, lead to a discharge of toxic and undegradable effluents into receiving streams. The assessment of potential adverse effects of influents entering the waste water treatment plant is for this reason necessary. The aim of the study was to predict a suitability of discharging the industrial waste water into waste water treatment plants based on the assessment of waste water toxicity and biodegradability. The waste water sample, originating from the industry producing fire protection materials, was highly polluted with organic substances. At first, the acute toxicity of the investigated sample was determined using activated sludge measuring oxygen consumption rates. It was found that the waste water sample was acutely toxic to microorganisms. Ready biodegradability of waste water was determined in a closed respirometer by measuring oxygen consumption. As diluted samples of the waste water were not readily biodegradable inherent biodegradability of the waste water sample was evaluated using the ZahnWellens test. It was found that diluted samples were inherently biodegradable probably due to the fact that higher concentration of microorganisms of activated sludge was added. It can be concluded that the tested waste water could be discharged into the sewerage system on the condition that a dilution of the tested waste water in the municipal waste water treatment plant would be at least 1:20.

This paper reports how measurement traceability of results of field laboratories in the area of wastewater analysis can be demonstrated by participation in a proficiency testing scheme based on reference values. A description of the scheme, organized by the National Institute of Chemistry, Ljubljana, Slovenia, is given: preparation of test material, homogeneity and stability testing, reference measurements for establishing reference value and setting performance criteria for the participants. Reference values were obtained by validated methods, traceability to appropriate measurement references was established and measurement uncertainty was evaluated from combining uncertainty components. Results indicate that the majority of Slovenian laboratories analysing water operate under the appropriate traceability conditions. Laboratories participating in proficiency testing schemes that integrate metrological principles are able to demonstrate traceability to SI units and their measurement capability.

Effluents may contain hazardous chemicals, which could have adverse effects on aquatic ecosystems. Important intrinsic properties are toxicity and biodegradability of effluents and they should be assessed in order to protect the aquatic environment. Microorganisms of activated sludge are responsible for biological waste water treatment. The lack of treatment effectiveness could, in case of unexpected toxic influents to waste water treatment plants, lead to a discharge of toxic and undegradable effluents into receiving streams. The assessment of potential adverse effects of influents entering the waste water treatment plant is for this reason necessary. The aim of the study was to predict a suitability of discharging the industrial waste water into waste water treatment plants based on the assessment of waste water toxicity and biodegradability. The waste water sample, originating from the industry producing fire protection materials, was highly polluted with organic substances. At first, the acute toxicity of the investigated sample was determined using activated sludge measuring oxygen consumption rates. It was found that the waste water sample was acutely toxic to microorganisms. Ready biodegradability of waste water was determined in a closed respirometer by measuring oxygen consumption. As diluted samples of the waste water were not readily biodegradable inherent biodegradability of the waste water sample was evaluated using the Zahn-Wellens test. It was found that diluted samples were inherently biodegradable probably due to the fact that higher concentration of microorganisms of activated sludge was added. It can be concluded that the tested waste water could be discharged into the sewerage system on the condition that a dilution of the tested waste water in the municipal waste water treatment plant would be at least 1:20.

Measurement traceability is universally recognised as one of the basic prerequisites for comparability of results obtained in different laboratories and is a basic aspect of metrological sciences such as analytical chemistry. This requirement is underscored by the increasing adoption of standards and measurement quality systems, such as laboratory accreditation against ISO/IEC 17025. Testing laboratories ensure traceability of their measurement results by using appropriate reference standards for calibration of instruments and control of measurement processes. For routine work in the field of water analysis, these standards are usually commercial solutions or in-house solutions prepared from "pure" products. Therefore, laboratories should demonstrate that their use of reference standards is appropriate and sufficient, which can be done by participation in an appropriate proficiency-testing scheme. The paper reports how measurement traceability of results from field laboratories (nitrite nitrogen, nitrate nitrogen, chloride and sulphate; all in water) can be demonstrated by participation in a proficiency-testing scheme based on reference values.

The European Water Framework Directive (WFD) requires the identification of significant human pressures and impacts on water bodies. An important component in protecting the ecological quality of watercourses is the regulation of point discharges. New ecotoxicological approaches for the assessment of the influence of the point source of pollution on the receiving water are presented. The limitations of a substance-specific assessment make it impossible to satisfactorily assess effluents on the basis of their environmental hazard. The new strategy starts with the investigation of effluents (chemical analyses, toxicological and biodegradation studies, toxicity identification evaluation-TIE). Then the harmful substances from the effluents are traced in the receiving stream and the impact of these substances on the stream is determined in river water and sediments. In a case study this strategy was used for impact assessment of tannery and municipal wastewater on the river Ljubljanica. We investigated the impact of pollution by the tannery and municipal effluents upon the receiving water and sediments. At the highest measured river flow the concentrations of pollutants in the river were not significantly changed as a result of the impact of the point source of pollution. At average and critical river flows the concentrations of pollutants at the sampling site near the outflow of effluents were higher, but at a site distant from the source of pollution, the concentration decreased due to different physical, chemical and biological processes in the river (biodegradation, precipitation). River water was non-toxic in acute and chronic toxicity tests with Daphnia magna. Sediments have the ability to accumulate organic and inorganic toxic compounds. Increased amounts of chromium and aluminium in river sediments were found at the sampling site far from the source of pollution. From the results of our work it is evident that the limitation of effluent alone is not enough, and that for good river management it is essential to consider the receiving stream as well.

Wastewater from a tannery was investigated using chemical-specific analyses and assessment of the acute toxicity of the whole effluent over a 2-year period. The wastewater samples were overloaded with organic and inorganic compounds, and measured concentrations of the chemical parameters as well as dilution factors estimating acute toxicity, frequently exceeded the permissible limits for the discharge of wastewater from a tannery into the receiving stream. In the later part of the monitoring programme, the toxicity of the samples was significantly increased in comparison to the previous samples. The agent for hide disinfection was assumed to be the reason for the increased toxicity of the wastewater samples, and the extremely high acute and chronic toxicity of the agent to bacteria, algae, daphnids, and fish confirmed this suspicion. The most sensitive species was Daphnia magna; the 48 h EC50 was 0.70 x 10(-5)v/v% and the 21d IC25 was 0.40 x 10(-6)v/v% of the agent. After withdrawal of this highly toxic agent for hide disinfection from the technological process in the tannery, the toxicity of the wastewater declined to the previous level.