Bioremediation of chlorophenol-contaminated sawmill soil using pilot-scale bioreactors under consecutive anaerobic-aerobic conditions.

Chlorophenols (CPs), including pentachlorophenol (PCP), are chemicals of concern due to their toxicity and persistence. Here we describe a successful reactor-based remediation of CP-contaminated soil and assess changes in the toxicity patterns and bacterial communities during the remediation. The remediation consisted of separating half of the contaminated soil to be ground (samples M) in order to test whether the grinding expedited the remediation, the other half was left unground (samples P). Both soils were mixed with wastewater treatment sludge to increase their bacterial diversity and facilitate the degradation of CPs, and the resultant mixtures were placed in 2 bioreactors, M and P, operated for 16 months under anaerobic conditions to favor dehalogenation and for an additional 16 months under aerobic conditions to achieve complete mineralization. Samples were taken every 4 months for toxicity and microbial analyses. The results showed a 64% removal of total CPs (ΣCPs) in reactor P after just 18 months of remediation, whereas similar depletion in reactor M occurred after ∼25 months, indicating that the grinding decelerated the remediation. By the end of the experiment, both reactors achieved 93.5-95% removal. The toxicity tests showed a decrease in toxicity as the remediation progressed. The succession of bacterial communities over time was significantly associated with pH, anaerobic/aerobic phase and the concentration of the majority of CP congeners. Our data indicate that the supplementation of contaminated soil with sludge and further incubation in pilot-scale bioreactors under consecutive anaerobic-aerobic conditions proved to be effective at the remediation of CP-contaminated soil.

The reproduction of Enchytraeus sp.--technical improvement for the counting of juveniles.

Soil-dwelling annelids of the genus Enchytraeus are used in ecotoxicology for testing of chemicals mixed in artificial soil or for testing of wastes and soils of unknown quality. ISO 16387 describes a method for determining the effects of substances or contaminated soils on survival and reproduction of Enchytraeus albidus or of the smaller species Enchytraeus buchholzi or Enchy-traeus crypticus. After the total test duration of 6 (or 4) weeks, the juveniles hatched in the meantime are counted. There are several possible extraction techniques, which are always followed by counting the juveniles by hand, but none of them seems easy to handle. We proposed a new modification of the worm extraction method using flotation of fixed and stained juveniles followed by taking a photograph. The digital image of the juveniles is evaluated by computer processing. It makes the counting of juveniles much easier and less labor intensive.

Phytotoxicity tests of solid wastes and contaminated soils in the Czech Republic.

BACKGROUND, AIM, AND SCOPE: The purpose of this study was to compare the suitability of different phytotoxicity testing procedures for the evaluation of toxicity associated with both soil contamination and solid wastes, both of which can be of environmental risk to plants. Ten different representative types of contaminated soils and solid waste samples were chosen from the Czech Republic. MATERIALS AND METHODS: Both solid-phase and aquatic toxicity testing procedures on mono- and dicotyledonous plants were performed using Lactuca sativa L., Sinapis alba L., Hordeum vulgare L., Triticum aestivum L., Lemna minor L., and the chlorococcal algae Desmodesmus subspicatus (syn. Scenedesmus subspicatus), strain BRINKMANN: 1953/SAG 86.81. An innovative classification scheme, using the intensity of toxic effects upon the plants, is presented in the study. Detailed chemical characterizations of both solid samples and their aquatic elutriates were carried out, using the appropriate ISO guidelines. In the solid samples, all the congeners of polychlorinated biphenyls were analyzed, together with 16 U.S. EPA polyaromatic hydrocarbons, the aggregate of C10-C40 hydrocarbons, total organic carbon, extractable organic halogens, as well as the majority of the environmentally toxic metals. In the aquatic elutriates, parameters analyzed were pH, conductivity, dissolved organic content, phenol index, main anions, and the majority of the environmentally relevant metals. RESULTS: Eight out of ten samples tested expressed phytotoxic properties on tested organisms. Only three of the samples were toxic to both aquatic and terrestrial organisms in the tests. This demonstrates how different substances present in different samples can express different types of toxic effects, resulting in the illogical substituting terrestrial bioassays with aquatic ones. DISCUSSION: Based upon our experience, we propose the following battery of bioassays for use in the characterization of toxic properties of solid wastes and contaminated soils: Aquatic ecosystems were tested by the algae D. subspicatus and plant L. minor; and the terrestrial ecosystems were tested by the dicotyledonous L. sativa and monocotyledonous H. vulgare. This proposed new battery of bioassays for the detection of phytotoxicity of both solid wastes and contaminated soils has higher sensitivity (as well as greater ecological relevance) compared to the battery of bioassays currently used in the Czech Republic. CONCLUSIONS: The tests currently used for regulatory purposes in the Czech Republic are phytotoxicity tests of elutriates, using S. alba and D. subspicatus, which have been found insufficiently sensitive to the range of different pollutants present in contaminated soils and/or solid wastes. If only aquatic bioassays are used for the toxicity testing, it is possible that the toxic effects of substances (poorly or totally) insoluble in water might be underestimated. The new proposed system of toxicity classification has proven to be both practical and sensitive. RECOMMENDATIONS AND PERSPECTIVES: This recommended alternative battery of phytotoxicity tests includes both aquatic tests of waste elutriates (with the algae D. subspicatus along with the aquatic plant L. minor), in addition to tests of the terrestrial solid samples (with the dicotyledonous L. sativa and the monocotyledonous H. vulgare). This battery of bioassays is sufficiently sensitive, representing a majority of types of aquatic and terrestrial plants.

Ecotoxicity monitoring of hydrocarbon-contaminated soil during bioremediation: a case study.

The ecotoxicity of hydrocarbon-contaminated soil originating from a brownfield site was evaluated during a 17-month biodegradation pilot test. The initial concentration of total petroleum hydrocarbons (TPHs) in the soil was 6380 microg/g dry weight. An amount of 200 kg soil was inoculated with 1.5 L of the bacterial preparation GEM-100 containing Pseudomonas sp. and Acinetobacter sp. strains (5.3 x 10(10) CFU.mL(-1)) adapted to diesel fuel. The concentration of TPHs in the soil decreased by 65.5% after bioremediation. Different organisms such as the bacterium Vibrio fischeri, terrestrial plants Sinapis alba, Lactuca sativa, and Hordeum vulgare, the water plant Lemna minor, the earthworm Eisenia fetida, and the crustacean Heterocypris incongruens were used for ecotoxicity evaluation. The highest toxicity was detected in the first period of bioremediation. However, certain toxic effects were detectable during the whole bioremediation process. The contact tests with plants, earthworms, and crustaceans were the most sensitive of all of the bioassays. Therefore, the contact tests performed directly on soil samples were shown to be a better tool for ecotoxicity evaluation of hydrocarbon-contaminated soil than the tests performed on soil elutriates. The ecotoxicity measured by the responses of the tests did not always correlate with the decrease in TPH concentrations in the soil during bioremediation.