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This study investigates the risk to contamination of groundwater in public water supply wells in the Koprivnica-Križevci county (northwest Croatia). Five physicochemical parameters were monitored in all groundwater samples from 2008 to 2017 to identify major differences between the wells, assess temporal variations and understand the capacity for rainfall to alter groundwater pollution loadings. Multivariate discriminant analysis showed statistically significant differences between the six sampled wells based on the analyzed parameters (Wilks' lambda: 0.001; F = 26.2; p 4/oxidizability and to a lesser extent, pH). The time series data showed disparate trends, with nitrate concentrations increasing, whereas pH and KMnO4 decreased, while electrical conductivity and chloride levels remained stable. Although rainfall can impact groundwater pollution loadings through dilution processes in aquifers, the resulting fluctuations in physicochemical parameters are complicated by variations in rainfall events and local topography, as well as from climate change. Therefore, it is important to predict the contamination of groundwater quality in the future using machine learning algorithms using artificial neural network or similar methods. Multivariate statistical techniques are useful in verifying temporal and spatial variations caused by anthropogenic factors and natural processes linked to rainfall. The resulting identified risks to groundwater quality would provide the basis for further groundwater protection, particularly for decisions regarding permitted land use in recharge zones.

Caddisfly faunistic and ecological features were studied at 14 sampling sites along the catchment area of the Dobra River. Adults were collected monthly, over a period of 13 months (from early November 2009 until the end of November 2010), using ultraviolet (UV) light trap and entomological net. Physico-chemical parameters of water and air were also measured at all sampling sites. The study encompassed several segments of caddisfly fauna: the composition, new records, the distribution of all recorded species and seasonal dynamics. A total number of 77 species were recorded, out of which 15 species and four genera were new records for Croatian caddisfly fauna. The CCA analysis showed that the water temperature and the altitude had the highest impact on distribution of caddisfly fauna in this area. The results of this study contribute to the increase of faunistic and ecological knowledge of the Croatian caddisflies.

The aim of this research was development of appropriate procedure for the treatment of landfill leachate taken from the Visevac, Mraclinska Dubrava and Piskornica sanitary landfills. Due to the complex nature of the effluents a combined treatment approach was applied. The pretreatment step included simultaneous treatment with calcium oxide and electrocoagulation/electrooxidation by stainless steel electrode set. The main treatment included electrocoagulation/electrooxidation using the set of stainless steel, iron and aluminum electrodes. The pretreatment allowed the destruction and/or coagulation of the high molecular weight organic substances as well as optimization of pH values for the formation of reactive oxidative species, and the transformation of NH(4)-N into volatile NH(3)-N. In the presence of added calcium oxide and electrochemically generated coagulant the removal of the fluorides, phosphates and heavy metals occur through the formation of poorly soluble fluorapatite, hydroxyl apatite, and various hydroxides. During the main treatment electrochemically generated reactive oxidative species carried out rapid decomposition of the organic matter and ammonia, resulting in the removal of COD from 74.9% to 94.2%, color from 98.8% to 99.7%, turbidity from 98.4% to 99.3%, suspended solids from 97.1% to 99.3%, and ammonia from 99.6% to 99.7%. Slightly better results for the removal efficiency of color, turbidity and suspended solids were obtained in the case of Piskornica landfill compared with the other two landfills, while the COD removal efficiency decreases in the following order: Piskornica >Mraclinska Dubrava >Visevac. This could be related to the age of the landfill, which increases in the same order. Consequently, with the increasing age of the landfill the degree of degradability of the organic matter reduces significantly. Applied treatment approach resulted in clear, colorless and odorless effluent with the values of all measured parameters significantly lower compared to the upper permissible limit for discharge into the environment.

In vitro genotoxic effects of leachates of electric arc furnace dust (EAFD) on human peripheral lymphocytes, assessed prior and following the treatment with a strong alkaline solution were investigated using the alkaline comet assay. Prior and following the treatment, lymphocytes were incubated with leachate of EAFD for 6 and 24 hours at 37 degrees C. Negative controls were also included. Mean values of the tail lengths established in the samples treated with the leachate stemming from the original dust for 6 and 24 hours, were 15.70 microm and 16.78 microm, respectively, as compared to 12.33 microm found in the control sample. Slight, but significant increase in the tail length was also found with the dust treated with a strong alkaline solution (13.37 microm and 13.60 microm). In case of high heavy metal concentrations (the extract of the original furnace dust), the incubation period was revealed to be of significance as well. The obtained results lead to the conclusion that alkaline comet assay could be used as a rapid, sensitive and low-cost tool when assessing genotoxicity of various waste materials, such as leachates of the electric arc furnace dust.

Landfill leachate presents hardly treatable, highly complex and very toxic environmental effluent originated in the municipal solid waste degradation process. Although, numerous treatment methods were developed so far, none of them alone could achieve permissible limits of the primary pollutants to discharge into natural recipients. The current study aimed to develop and apply the process to treat landfill leachate by simultaneous application of electrochemical methods, ultrasound, electromagnetic field and ozonation to achieve the legal criteria for its discharge into natural recipient and minimize its adverse environmental impacts. For this purpose, old landfill leachate was taken from the Piskornica (Koprivnica, Croatia) sanitary landfill. Prior to the treatment, the leachate was supplemented with NaCl (2 g/L) and subjected to simultaneous treatment with stainless steel electrode plates, ultrasound and recirculation through electromagnetic field. After 45 minutes, stainless steel electrode plates were replaced by iron electrodes and treated for another 10 minutes followed by 15 minutes of the treatment with aluminum electrode plates. Ultrasound and recirculation through electromagnetic field were also applied during Fe and Al electrode treatment. Finally, the electrodes were removed and the suspension was mixed with ozone for another 30 minutes and allowed to settle for an hour. Following the combined treatment, the removal efficiency for the turbidity, color, suspended solids, ammonium, phosphates and heavy metals was 99% or higher, while the removal of COD was 97%. All the measured parameters in the treated leachate were lower compared to upper permissible limit for discharge into natural recipient.

In this research, toxicological safety of two newly developed methods for the treatment of landfill leachate from the Piskornica (Croatia) sanitary landfill was investigated. Chemical treatment procedure combined chemical precipitation with CaO followed by coagulation with ferric chloride and final adsorption by clinoptilolite. Electrochemical treatment approach included pretreatment with ozone followed by electrooxidation/electrocoagulation and final polishing by microwave irradiation. Cell viability of untreated/treated landfill leachate was examined using fluorescence microscopy. Cytotoxic effect of the original leachate was obtained for both exposure periods (4 and 24 h) while treated samples showed no cytotoxic effect even after prolonged exposure time. The potential DNA damage of the untreated/treated landfill leachate was evaluated by the comet assay and cytokinesis-block micronucleus (CBMN) assay using either human or plant cells. The original leachate exhibited significantly higher comet assay parameters compared to negative control after 24 h exposure. On the contrary, there was no significant difference between negative control and chemically/electrochemically treated leachate for any of the parameters tested. There was also no significant increase in either CBMN assay parameter compared to the negative control following the exposure of the lymphocytes to the chemically or electrochemically treated landfill leachate for both exposure periods while the original sample showed significantly higher number of micronuclei, nucleoplasmic bridges and nuclear buds for both exposure times. Results suggest that both methods are suitable for the treatment of such complex waste effluent due to high removal efficiency of all measured parameters and toxicological safety of the treated effluent.

A combined treatment approach using advanced oxidation, electrochemical methods and microwaves was developed and applied for the treatment of landfill leachate taken from Piskornica (Koprivnica, Croatia) sanitary landfill. Due to the complex nature of the effluent and extremely low bio-degradability (BOD(5)/COD ratio = 0.01) the purification of the leachate started with pre-treatment with ozone followed by simultaneous ozonation and electrocoagulation/electrooxidation using the set of iron and aluminum electrodes, and finally, the degradation of organic residue and ammonia with microwaves. Applied treatment approach resulted in clear, colorless and odorless effluent with the values of all measured parameters significantly lower compared to the upper permissible limit for discharge into the environment. The removal percentages of the parameters: color, turbidity, suspended solids, ammonia, COD and iron following the combined treatment were 98.43%, 99.48%, 98.96%, 98.80%, 94.17% and 98.56%, respectively.

The aim of this research was development of appropriate procedure for treatment of landfill leachate taken from old sanitary landfill Piskornica (Koprivnica, Croatia). Due to complex nature of the effluent a combined treatment approach was applied. Samples were treated with calcium oxide followed by ferric chloride and finally with clinoptilolite. The optimum amount of treating agents and contact time were determined. Application of calcium oxide (25 g/L, 20 min. contact time) resulted in the reduction of color, turbidity, suspended solids and ammonia for 94.50%, 96.55%, 95.66% and 21.60%, respectively, while the removal efficiency of Cr (VI), Fe, Ni, Cu, Zn and Pb was 75.00%, 95.34%, 56.52%, 78.72%, 73.02% and 100.00%, respectively. After addition of ferric chloride (570 mg Fe(3+)/L, 20 min. contact time) removal efficiency of color, turbidity, suspended solids and ammonia increased to 96.04%, 99.27%, 98.61%, and 43.20%, respectively. Removal of ammonia (81.60%) increased significantly after final adsorption onto clinoptilolite (25 g/L, 4 h contact time). Removal of COD after successive treatment with calcium oxide, ferric chloride and clinoptilolite was 64.70%, 77.40% and 81.00%, respectively.

The purpose of this work was development of an appropriate procedure for the neutralization/purification of electroplating wastewater (EWW) with alkaline solid residue (ASR) by-product of the alkaline extraction of zinc and lead from electric arc furnace dust (EAFD). Removal efficiency of ASR at optimum purification conditions (pH 8 and mixing time; 20 minutes) for the elements Pb, Cr (VI), Cr (III), Fe, Ni, Cu and Zn were 94.92%, 97.58%, 99.59%, 99.48%, 97.25% and 99.97%, respectively. The concentrations of all elements in the purified wastewater were significantly lower in relation to the upper permissible limit for wastewaters suitable for discharge into the environment. The remaining waste mud was regenerated in the strong alkaline medium and successfully applied once again for the neutralization/purification of EWW. Removal efficiencies of heavy metals accomplished with regenerated waste mud were comparable to these achieved by original ASR. Elemental concentrations in the leachates of the waste mud were in accordance with regulated values.