Abstract Dyes are recalcitrant compounds that resist conventional biological treatments. The degradation of three textile dyes (Indigo, RBBR and Sulphur Black), and the dye-containing liquid effluent and solid waste from the Municipal Treatment Station, Americana, São Paulo, Brazil, by the cyanobacteria Anabaena flos-aquae UTCC64, Phormidium autumnale UTEX1580 and Synechococcus sp. PCC7942 was evaluated. The dye degradation efficiency of the cyanobacteria was compared with anaerobic and anaerobic-aerobic systems in terms of discolouration and toxicity evaluations. The discoloration was evaluated by absorption spectroscopy. Toxicity was measured using the organisms Hydra attenuata, the alga Selenastrum capricornutum and lettuce seeds. The three cyanobacteria showed the potential to remediate textile effluent by removing the colour and reducing the toxicity. However, the growth of cyanobacteria on sludge was slow and discoloration was not efficient. The cyanobacteria P. autumnale UTEX1580 was the only strain that completely degraded the indigo dye. An evaluation of the mutagenicity potential was performed by use of the micronucleus assay using Allium sp. No mutagenicity was observed after the treatment. Two metabolites were produced during the degradation, anthranilic acid and isatin, but toxicity did not increase after the treatment. The cyanobacteria showed the ability to degrade the dyes present in a textile effluent; therefore, they can be used in a tertiary treatment of effluents with recalcitrant compounds.

The Municipal Station of Americana, SP, Brazil, treats a volume of 400 l s-1 of effluent, of domestic and textile origin, and produces about 20 t of sludge per day. The plant horseradish, which contains high amount of peroxidases, was able to decolorize this effluent in 2 h and the solid waste in 2 days, at concentrations of 10 and 50%, respectively. However, there was an increase in the toxicity for the bioassays with Hydra attenuatta, Selenastrum capricornutum and lettuce seeds, indicating formation of more toxic substances. Since horseradish showed the ability to decolorize these residues, it can be used as pre-treatment resulting in a sludge of less complex composition.

A degradação do herbicida diuron foi estudada em solo com e sem histórico de aplicação obtendo-se aproximadamente degradação sete vezes maior no solo com histórico de aplicação, após 64 dias de incubação. Houve um aumento no número de bactérias no solo com histórico de aplicação de 3.3 x 10 6 para 1.9 x 10(8) UFC. g-1 solo. Não houve aumento na biomassa após a incubação, porém foi encontrado significante resíduo de 14C-diuron na biomassa. Um consórcio de três bactérias foi isolado, Acinetobacter johnsonii e duas espécies de Bacillus sp., em meio contendo diuron como única fonte de carbono. Somente A. johnsonnii foi capaz de crescer sozinha em meio contendo diuron como única fonte de carbono.

Studies were carried out on the isolation of diuron-degrading bacteria from treated soil. The mineralization of 14C-diuron in soil following a three-year application and in soil without previous application were 68.95 mug.100 g-1 and 24.16 mug.100 g-1, respectively, after a 64-day incubation period. In the first soil there was a significant increase in the number of bacteria, from 3.3 x 10 6 to 1.9 x 10(8). The microbial biomass did not change, however, a significant 14C-residue of diuron was found in the microbial biomass. A consortium of three bacteria, Acinetobacter johnsonii and two Bacillus spp., was isolated in medium containing diuron as the only carbon source. Only A. johnsonii was able to grow alone in medium with diuron as the only carbon source.