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Oily wastewater is becoming a concern worldwide due to its quantities and the presence of contaminants and its sustainable treatment should be cost-effective and meet all requirements so the contaminants are not transferred to the environment. The paper reviews the state-of-the- art in the oily wastewater treatment by electrochemical processes such as electrochemical advanced oxidation processes and electrocoagulation. Efficiency of oily wastewater treatment has been thoroughly investigated with its expression as a function of the main technological (process) parameters. Fe and Al electrodes, as well as their combination have proven to be very effective in oily wastewater treatment with slightly better performance of Al electrodes. Higher current densities and longer reaction times result with higher COD, TOC, turbidity, phenol and oil and grease removal efficiencies, but with resulting increase in wastewater temperature and energy consumption, so there is a strong need for the process optimization. There is a need for further research on the treatment efficiencies of different contaminants (heavy metals, total hydrocarbons, organic halogens, cyanides, etc.). A lack of research is presented on the treatment efficiency with electrodes of different materials as well as the analyses of the sludge production and its further treatment and use or disposal.

It was demonstrated in the previous work that various threat materials could be detected inside the sea going cargo container by measuring the three variables, carbon and oxygen concentration and density of investigated material. Density was determined by measuring transmitted neutrons, which is not always practical in terms of setting up the instrument geometry. In order to enable more geometry flexibility, we have investigated the possibility of using the scattered neutrons in cargo material identification. For that purpose, the densities of different materials were measured depending on the position of neutron detectors and neutron generator with respect to the target position. One neutron detector was put above the target, one behind and one in front of the target, above the neutron generator. It was shown that all three positions of neutron detectors can be successfully used to measure the target density, but only if the detected neutrons are successfully discriminated from the gamma rays.

The aim of this work was the development and application of the pilot plant with the capacity of 1000 L/day for the purification of groundwater used for human consumption characterized with high concentration of arsenic and increased values of organic pollutants, ammonia, nitrites, color and turbidity. For that purpose, groundwater from the production wells supplying the towns Zrenjanin and Temerin (Vojvodina, Serbia) was used. Due to its complex composition, the purification system required the combination of the electroreduction/electrocoagulation, using iron and aluminum electrode plates with/without ozonation, followed by the electromagnetic treatment and the finally by the simultaneous ozonation/UV treatment. The electroreduction was used for the removal of nitrates, nitrites, and Cr(VI), while the removal of arsenic, heavy metals, suspended solids, color and turbidity required the application of the electrocoagulation with simultaneous ozonation. Organic contaminants and ammonia were removed completely in the last treatment step by applying the simultaneous ozonation/UV treatment. All measured parameters in the purified water were significantly lower compared to the regulated values. Under the optimum treatment conditions, the removal efficiencies for color, turbidity, suspended solids, total arsenic, total chromium, Ni(II), total copper, sulfates, fluorides, chemical oxygen demand, ammonia, nitrates, and nitrites were 100%. The removal efficiencies of the total manganese and iron were 85.19% and 97.44%, respectively, whilst the final concentrations were 4 and 7 μg/L, respectively.

The aim of the research reported here is the development of a methodology for the measurement of small scale variations in chemical elements concentrations, in particular of carbon - oxygen ratio. Knowledge of the C/O ratio is of importance to many problems in various fields. Here we single out the application in obtaining important information about the oilfields. The most fundamental reservoir parameters - oil, gas and water content - are critical factors in determining how each oilfield should be developed. It is well established that carbon to oxygen ratio log yields accurate and repeatable data that can be used to identify and monitor reserves depletion. Recent improvements in neutron generator and gamma detector technologies resulted in small devices which allowed through-tubing measurements. Although the ratio of carbon and oxygen yields is a measure of the ammount of oil arround the tool it should be realized that a carbon signal can originate from several sources including the borehole, the cement behind the casing, the formation rock and the formation fluid. In order to evaluate these contributions individualy we are proposing the modification of the neutron generator by insertion of segmented associated alpha particle detector. From the measurement of time of flight spectra (alpha particle detector - start signal; gamma ray detector - stop signal) it would be possible to determine the location of gamma ray producing voxel and in such a way to determine radial variations in several chemical elements concentrations, in particular of carbon to oxygen ratio.

Variety of objects found on the sea floor need to be inspected for the presence of materials that represent threat to the environment and human safety. We have demonstrated that a sealed tube 14 MeV neutron generator, with the detection of associated alpha particles, can be used underwater when mounted inside a remotely operated vehicle equipped with hydraulic legs and a variety of sensors for the inspection of such objects for the presence of threat materials.

An ROV constructed for the inspection of objects lying on the coastal sea floor has been described. In order to establish if an object on the sea floor contains some sort of threat material (explosives, chemical agent), a system using a neutron sensor installed within ROV has been developed. We describe the maritime properties of ROV and show that the measured gamma spectra for commonly found ammunition charged with TNT explosives are dominated by C, O and Fe peaks enabling the determination of the presence of explosives inside an ammunition shell.

Tagged neutron inspection system was used for the underwater detection of explosives. Neutrons were produced in the d + t nuclear reaction with API 120 sealed tube neutron generator. Five kilograms of TNT explosive were measured in a pool filled with water. Measurements were done in target in, target out configuration. Also, a sandwich made of 6 mm thick iron plates with explosive placed between two layers of sea sediments was measured under the same conditions. Sediments were collected in the Adriatic Sea. Measurements were repeated with TNT explosive replaced by rocks of similar size and shape. Neutron tube was rotated in order to find the position of explosive (rocks) in the sandwich. It was found that TNT can be detected underwater and that is possible to distinguish TNT from the sea rocks placed between 6 mm thick iron plates or between layers of sediments by their ratios of carbon and oxygen.

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.

Water extracts genotoxicity of the coagulant produced from industrial waste (red mud and waste base) and its waste mud remained after waste water treatment by the coagulation/flocculation process were studied. Tests were conducted in order to confirm nontoxicity of this new product prior to commercial production and usage and also to recommend a safe way for a handling and disposal of the remaining waste material. The toxicity investigation included (i) determining frequency of the cell survival, (ii) the Ames assays, (iii) micronucleus assay, and (iv) cell proliferation kinetics (expressed as mitotic index). These techniques were also employed in toxicity testing of the different concentrations of metal salts, zinc chloride, and lead nitrate in this case since these two elements were present in high concentrations in the waste water intended for the purification with the new coagulant. Mixture of metal salts in the concentrations that represent maximum allowed values for water extracts of technological waste was also tested. Two strains of Salmonella typhimurium, TA98, and TA100 were used for determining cytotoxicity and for the Ames test, while the cytogenetic investigations were performed on human peripheral blood lymphocytes. Water extracts of the coagulant and its waste mud did not induce a significant increase of the micronuclei in human peripheral blood lymphocytes. They also did not disturb lymphocyte proliferation kinetics in vitro. As regards lead nitrate it proved not to be cytotoxic on bacterial strains in the tested concentration range (1-100 mg/L), whereas zinc chloride showed cytotoxic effect for the concentrations above 25 mg/L. The Ames test results for the noncytotoxic concentrations of these metals were negative. Comparing to the negative control a significantly higher number of the micronuclei was determined after the treatment of the whole blood with 100 mg/L of zinc chloride, as well as with 10 and 100 mg/L of lead nitrate. A linear, dose dependent increase was obtained for both salts. Similar results were obtained on the basis of the mitotic index.

Distributions of trace elements in the coastal sea sediments of Punat Bay in the Northern Adriatic have been investigated. The concentrations of 16 elements (Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Br, Rb, Sr, Y, Zr and Pb) were measured by energy dispersive XRF. Two predominant types of sediments were observed: the first (sediment “A”), which consists of 87% pelitic fraction and the second (sediment “B”), where coarse-grained fraction (0.315–0.1 mm) prevails. Enrichment factors had elevated values in two upper-most segments for the elements Cu, Zn and Pb in sediment “A.” The highest percentage of exchangeable fraction with respect to the total composition was characteristic for Cr, Cu and Zn in both types of sediments. By means of the linear regression analysis it was established that metals present in the antifouling paints were dispersed all over the bay because of an inefficient cleaning mechanism, poor communication with the open sea, and the good mixing of water and suspended mater in the ba...

Proposal for coagulant production using red mud and waste base as row material, by-products of abandoned alumina factory near Obrovac in Croatia, is described. Basic physico-chemical characteristics of red mud and waste base were also given. Elemental concentrations of red mud, waste base and wastewaters before and after treatment were measured using tube excited EDXRF method. Coagulant production consist of partial dissolution of red mud with diluted sulphuric acid (30% wt), separation of liquid from residual red mud by centrifugation or filtration through the filter press, and neutralisation of acid red mud (pH = 0) with the waste base to pH = 8. This process of red mud neutralisation results in heavy metals removal and also neutralisation of waste base to pH = 8, which could be, after treatment, discharged directly into the environment. Resulting red mud, after neutralisation, is in gel-like state and is suitable for heavy metals and turbidity removal from industrial wastewaters. As an example, wastewaters from pressure washing of boats coated with antifouling paints were used and promising results were obtained. With one dose of coagulant (activated red mud), five cycles of heavy metals removal could be done.