Industrial wastewater as a source of external organic carbon for the biological nutrient removal.

Addition of external organic carbon source for denitrification is generally used in wastewater treatment plants (WWTPs) to intensify nitrogen removal processes. The aim of the laboratory survey was to measure the composition of concentrated industrial wastewater, determine the possibilities of its use as an external denitrification substrate, and assess its overall impact on WWTP. The obtained results demonstrate that the analysed industrial wastewater is biodegradable, and can be used as a denitrification substrate without special adaptation of biomass. The denitrification rates with tested wastewater were in the range of 1.6 to 1.9 mgN/g·h. Negative influence of long-term dosing of industrial wastewater on activated sludge were not confirmed. The effect of imported wastewater on WWTP must be assessed comprehensively, including the impact of heavy metals from wastewater on the sludge quality. The instructions on how to calculate this balance are provided in the article.

In-situ sulphide control in the anaerobic co-digestion of residual biomass from the production of penicillin and cystine.

This study was focused on the anaerobic digestion of residual biomass from the production of penicillin and l-cystine. The biogas potential tests of individual substrates and their mixture showed good anaerobic biodegradability. The highest measured specific biogas production was 712 l/kg volatile solids (VS) for penicillin biomass and 676 l/ kg VS for cystine biomass. The biogas potential tests were performed at different inoculum-to-substrate ratios (ISR) and showed that high concentrations of nitrogen and sulphur present in residual biomass have a major impact on the anaerobic processes. The long-term operation of the laboratory anaerobic reactor showed that the mono-digestion of the penicillin biomass was stable at an OLR of 1 kg/(m3.d). When co-digestion of penicillin and cystine biomass at a ratio of 0.9:0.1 (on a VS basis) and at the same OLR was enhanced, the operation of the laboratory model turned unstable. During this phase of the operation, the course of anaerobic processes was affected by ammonia and especially sulphide inhibition. Sulphide inhibition was effectively reduced by direct dosing of FeCl2 (in-situ sulphide control), at a molar iron-to-sulphur ratio of ß = 1 (mol Fe/mol S). When suppressing sulphide inhibition, the operation of the laboratory model became stable even at a co-digestion ratio of 0.5:0.5 (VS basis). The results of this work open a new scope for future applications in the anaerobic digestion of waste biomass with high sulfur content, coming from industrial fermentation processes.

Indirect electrochemical determination of sulfates in mineral water by a flow-through system.

The paper describes the indirect determination of sulfates by in-electrode coulometric indication method. The principle of the determination of sulfates consists in the on-line coupling of the exchange column filled with barium chromate and the flow-through coulometric analyser. In the column BaCrO4(s) converts to BaSO4(s) according to the equation: BaCrO4(s)+SO42-(aq)→BaSO4(s)+CrO42-(aq). This conversion is caused by the lower solubility of BaSO4(s) compared to the solubility of BaCrO4(s). Subsequently, the concentration of the chromate in the eluate solution was determined by the in-electrode coulometric indication method in the electrode made of reticulated vitreous carbon. The solution flowing out of the column was mixed in the flow-through analyser with 0.4 mol L-1 hydrochloric acid and the concentration of chromates was determined by direct reduction of Cr(VI) to Cr(III) with a constant current. The determination was evaluated by the calibration curve method. The linear range of the calibration curve was 3.9-100 mg L-1. The detection limit and the accuracy were 1.3 mg L-1 and 3.2%, respectively. The interference of the bicarbonate was eliminated through a conversion to insoluble carbonate by boiling the sample. The procedure was validated by analyses of certified reference material and bottled mineral water samples. A good agreement with the ion chromatography was achieved for all samples.

Anaerobic digestion of waste biomass from the production of L-cystine in suspended-growth bioreactors.

Waste biomass from the industrial production of the amino acid L-cystine contains above-average concentrations of organic pollutants and significant concentrations of nitrogen and sulfur. The specific biogas production (SBP) of waste biomass was monitored in parallel suspended-growth laboratory anaerobic bioreactors. After severe inhibition was observed, three different procedures were applied to inhibited reactor sludge to counter-attack the inhibitory effects of sulfides, respectively hydrogen sulfide: micro-aeration, dilution with water and precipitation by ferrous iron cations. The performance of bioreactors was weekly monitored. Organic loading rates (as chemical oxygen demand, COD) ranged from 1.07 to 1.97 g L(-1) d(-1). At the end of the experimentation, SBP averaged 217, 300 and 320 l kg(-1) COD with a methane content of 21%, 52% and 54%; specific sludge production averaged 133, 111 and 400 g total solids kg(-1) COD, and inhibition was 49%, 27% and 25%; for the applied procedures of micro-aeration, dilution and precipitation respectively.