Inovative in situ remedial techniques-kowledge transfer and practical experience

In situ chemical oxidation (ISCO) is one of promising remediation technologies applied within the Central and Eastern Europe. Type and extent of contamination, as well as treated matrix and an application method are driving parameters for determining, which of oxidation agents or their combinations are the best choice for set site conditions. Laboratory experiments of Fenton’s reagent, potassium permanganate and sodium persulphate (activated and nonactivated) plus conclusions of selected pilot-scale tests are discussed. Information on a possible combination of ISCO with surfactants is further given. Biologically enhanced reductive dechlorination (bio-ERD) offers a potential for destruction of chlorinated ethenes by an addition of a suitable electron donor directly to a contaminated ground. Organic by-products or processing waste of a food industry (e.g. beet molasses, stillage, whey) represent suitable as well as low-cost alternative electron donors for boosting this process. Results of laboratory experiments and a pilot-scale test performed on site heavily contaminated by chloroethylenes are presented. Nano zero-valent iron (nZVI) has 20 to 30-times higher reactivity then conventional ZVI, and thus this aspect is often stated as a main advantage of its usage (as a contrariety to its high price). Stoichiometry and passivation of nZVI active surface by reaction by-products are closely associated together and this fact directly influences practical efficacy this material. Experimental testing of various nZVI reactivity on Cr(VI+) and results of a pilot-scale on a site polluted by chlorinated hydrocarbons and petroleum substances are discussed. Moreover, bio-ERD and nZVI can be successfully combined in order to speed up remedial process, stabilise its performance and to cut clean-up financial costs. During this remedial train, nZVI generally accelerates establishment of anaerobic conditions in the ground and makes the first decomposition step (chemical reduction) of targeted pollutants. Later, the bio-ERD process finishes contamination treatment and, in general, returns back natural conditions onto a remediated site.