Evaluation of anaerobic biodegradability of wastewater from tebuconazole manufacturing.

This study aimed to verify the biological anaerobic treatability of tebuconazole effluent manufacturing. For this purpose, two preliminary batch tests were performed using an 'anaerobic respirometer' adjusting the initial pH of the effluent at 7.0 and 8.0, respectively (first phase). In addition, two tests (second phase) were run using sequential batch anaerobic fermenters, the first operated at different hydraulic detention times (10 and 16.7 days) and the second with different initial dilutions of the effluent (5 and 20%). The chemical oxygen demand (COD) removal observed on the anaerobic respirometer tests was in the range of 66-81%. According to the preliminary batch tests an optimal value of initial COD concentration and amount of biomass was identified, which was considered for the fermenters start up. However, it was observed that the optimal relation provided by the respirometer test was not a good parameter of operational control for the fermenters due to the accumulation of inhibitory substances, which affected the microbial activity and took the system to collapse. The initial dilution of the effluent (5 and 20%) was essential for the stability of the anaerobic system, allowing COD removals above 74% during this study.

Performance of UASB and DAEB reactors in the anaerobic digestion of synthetic wastewater containing sodium oleate and sodium stereate.

This study aimed at evaluating the performance of five laboratory-scale reactors, three UASB and two downflow anaerobic expanded bed (DAEB), fed with saccharose and long chain fatty acids (LCFA) for 410 days. Reactors operated at a temperature of 35 degrees C. The organic load rates were changed between 3.45 and 6.38 kg COD.m3.d(-1). During period I the substrate was saccharose and in periods II, III and IV it was saccharose plus sodium oleate, stereate and a mixture of sodium oleate and stereate. The UASB and DAEB reactors showed a similar performance. In UASB reactors specific methanogenic activity decreased in the periods II, III and IV. COD removal, biogas production and CH4 concentration in biogas decreased in all reactors at the end of the study. A washout occurred in UASB 2 and 3 when sodium stereate exceeded 500 mg.L(-1). In DAEB reactors the main problem was adsorption of LCFA particles onto the solid support.

Treatment of municipal wastewater UASB reactor effluent by unconventional flotation and UV disinfection.

Post-treatment of an UASB reactor effluent, fed with domestic sewage, was conducted using two-stage flotation and UV disinfection. Results were compared to those obtained in a parallel stabilisation pond. The first flotation stage employed 5 - 7.5 mg L(-1) cationic flocculant to separate off more than 99% of the suspended solids. Then, phosphate ions were completely recovered using carrier flotation with 5-25 mg L(-1) of Fe (FeCl3) at pH 6.3-7.0. This staged flotation led to high recoveries of water and allowed us to separate organic matter and phosphate bearing sludge. The water still contained about 1 x 10(2) NMP/100 mL total coliforms, which were removed using UV radiation to below detection levels. Final water turbidity was < 1.0 NTU, COD < 20 mg L(-1) O2 and 71 mNm(-1), the liquid/air interfacial tension. This flotation-UV flowsheet was found to be more efficient than the treatment in the stabilisation pond and appears to have some potential for water reuse. Results were discussed in terms of the biological, chemical and physicochemical mechanisms involved.

Low temperature conversion of sludge and shavings from leather industry.

Abstract Brazil has one of the largest herds of cattle in the world, with more than 170 million heads. Over 400 farms have exported more than 2,875 ton (in 1997) of leather to Europe. The wet blue tanning process uses chemicals such as chromium compounds and produces liquid wastes that must be treated by physicochemical and biological systems. About 15,000 ton per month of dewatering sludge with 24% solids content is disposed of into landfills. During the process, pre-tanned skins (wet blue leather) are shaved to the desired thickness and the shavings, like sludge, are among the wastes that must have special attention. The organic content and chromium concentration are high. About 12% of the leather production from cattle hides are shavings, and its chromium concentration ranges from 3.5 to 5.5% of dry matter. The Environmentally friendly leather project, a co-operation between Brazilian and German tanneries, universities and technical schools, is looking for process optimisation, waste minimisation and adequate treatment for solid and liquid wastes from the leather industry. This work presents results of Low Temperature Conversion of chrome-containing sludge and shavings in a laboratory batch reactor, offering a solution for these hazardous wastes, recovering the energy content and transforming metals in insoluble sulphides.

Biofilm development in down flow anaerobic fluidised bed reactors under transient conditions.

Biofilm development onto polypropylene particles (<4 mm) was studied in a laboratory-scale down flow anaerobic fluidised bed reactor. The reactor was fed with a synthetic solution containing sucrose and nutrients, and operated at 35 degrees C during 65 days at 44% bed expansion rate and 36 h HRT. Scanning electron microscopy (SEM) monitored the biofilm development. Initial adhesion occurred within the first 6 hours and after day 44 biofilm structure was complete. The presence of attached cells morphologically similar to Methanotrix bacilli and Methanosarcina sp. was observed by Scanning Electron Microscopy (SEM). The biofilm and the carrier surface roughness were measured by atomic force microscopy (AFM) and yielded 9.1 and 75 nm respectively. Results also showed good correlation between the SEM characterisation and the conventional anaerobic reactor parameters.