Marinko Markić

High salinity wastewater treatment.

The shock effect, survival and ability of activated sludge to acclimatize to wastewater containing different concentrations of NaCl and Na2SO4 were investigated under laboratory conditions. To accomplish this, the potential penetration of a sewage system by seawater as a consequence of storm surge flooding was simulated. The experiments were conducted using activated sludge taken from the aeration tank of a communal wastewater treatment plant and adding different concentrations up to 40 g/L of NaCl and 4.33 g/L of Na2SO4. The effects of salinity on the activated sludge were monitored for 5 weeks based on the values of pH, dissolved oxygen, total suspended solids, volatile suspended solids, sludge volume, sludge volume index, electrokinetic potential, respirometric measurements and enzymatic activity. The addition of salt sharply reduced or completely inhibited the microbial activity in activated sludge. When salt concentrations were below 10 g/L NaCl, microorganisms were able to acclimatize in several weeks and achieve the same initial activity as in raw sludge samples. When the salt concentration was above 30 g/L NaCl, the acclimatization process was very slow or impossible.

Influence of process parameters on the effectiveness of photooxidative treatment of pharmaceuticals

ABSTRACT In this study, UV-C/H2O2 and UV-C/ processes as photooxidative Advanced oxidation processes were applied for the treatment of seven pharmaceuticals, either already included in the Directive 2013/39/EU “watch list” (17α- ethynylestradiol, 17β-estradiol) or with potential to be added in the near future due to environmental properties and increasing consumption (azithromycin, carbamazepine, dexamethasone, erythromycin and oxytetracycline). The influence of process parameters (pH, oxidant concentration and type) on the pharmaceuticals degradation was studied through employed response surface modelling approach. It was established that degradation obeys first-order kinetic regime regardless structural differences and over entire range of studied process parameters. The results revealed that the effectiveness of UV-C/H2O2 process is highly dependent on both initial pH and oxidant concentration. It was found that UV-C/ process, exhibiting several times faster degradation of studied pharmaceuticals, is less sensitive to pH changes providing practical benefit to its utilization. The influence of water matrix on degradation kinetics of studied pharmaceuticals was studied through natural organic matter effects on single component and mixture systems.

Removal of Arsenic From Drinking Water — Croatian Experience

The groundwater of northern Croatia usually contains high concentrations of iron, manganese, ammonia and arsenic, and is therefore unsuitable for use as drinking water without the appropriate treatment. The existing water treatment plants in this area, applying conventional bio-filtration methods, remove iron, manganese and ammonia efficiently, but arsenic, appearing at concentration levels as high as 300 μg/L, is not removed. Thus, a simple and widely applicable water treatment procedure for the simultaneous removal of arsenic is needed. To find the most suitable water treatment procedure, several technologies employing adsorption, ion-exchange, and membrane processes were tested. A number of laboratory-scale and pilot-plant field experiments were performed on typical groundwater from numerous locations of northern Croatia. The results of the experiments undoubtedly indicate that the simplest and most efficient arsenic removal process from ground water is the adsorption of arsenic on iron(III) hydroxide. Moreover, this process is simply implemented on the existing water treatment facilities, ensuring that the arsenic concentrations in the effluent are as low as γ(As) < 10 μg/L.