V. Sklyar

Low temperature pre-treatment of domestic sewage in an anaerobic hybrid or an anaerobic filter reactor

The pre-treatment of domestic sewage for removal of suspended solids (SS) at a process temperature of 13 degrees C and an hydraulic retention time (HRT) of 4 h was investigated in an anaerobic filter (AF) and anaerobic hybrid (AH) reactor. The AF and the top of the AH reactor consisted of vertical sheets of reticulated polyurethane foam (RPF) with knobs. All biomass in the AF was only in attached form to avoid clogging and sludge washout. The AF reactor showed a significantly higher removal of total and suspended chemical oxygen demand (COD) than the AH reactor, respectively, 55% and 82% in the AF reactor and 34% and 53% in the AH reactor. Because the reactors were operated at a short HRT and low temperature, the hydrolysis, acidification and methanogenesis based on the influent COD were limited to, respectively, 12%, 21% and 23% for the AF reactor and 12%, 17% and 16% for the AH reactor. The excess sludge from the AH reactor was more stabilised and had a better settling capacity and dewaterability. However, the excess sludge from both the AH and AF reactors needed stabilisation. Therefore, the AF reactor is recommended for the pretreatment of domestic sewage at low temperatures.

Organic removal and microbiological features of UASB-reactor under various organic loading rates

Abstract The performance of a laboratory upflow anaerobic sludge blanket reactor (UASB-reactor) fed synthetic wastewater was investigated under organic loading rates (OLRs) ranging from 3·4 to 44·9 g COD/l·day. The distribution of substrates, intermediate byproducts, pH, VSS, specific sludge activities (acidogenic, acetoclastic, lithotrophic) and the number of different groups of microorganisms at different heights in the reactor were monitored. The conditions for active granular biomass formation were found for the OLRs investigated. When using high-flow UASB-reactors, attention should be paid to the efficient retention of the most active biomass circulating in the sludge blanket zone. The numbers of methanogens were one to two orders of magnitude higher in the lower part of the reactor (sludge bed zone) than in the upper part (sludge blanket zone). Electron micrographs of the granules showed that the predominant microbial biomass was Methanothrix. However, increasing the OLR led to a substantial increase of Methanosarcina in the granules. Significant amounts of other bacteria were found distributed within the granules between Methanothrix filaments.

The development of biological methods for utilisation and treatment of diluted manure streams

One possible solution for sustainable utilisation and treatment of diluted manure streams is preliminary separation of the solid and liquid fractions followed by separate biological treatment of both fractions. This approach was the starting point of a joint Russian-Dutch project: “The Development of Biotechnological Methods for Utilisation and Treatment of Diluted Manure Streams” (1996-1998). This paper describes the most important results of the project. The UASB process was found to be suitable for the pre-treatment of the liquid fraction of various types of manure using a lab-scale experimental set-up. The maximum organic loading rate (OLR) applied was approximately 12 g COD/1/day for hen or pig manure and 6 g COD/1/day for cattle manure using a hydraulic retention time (HRT) of about 1 day. The total COD reduction under these conditions was about 75% for the hen or pig manure and 42% for the cattle manure. The effluents obtained in this step can be used as liquid fertilisers (if possible) or should be post-treated to meet standards for discharge or reuse. Intensive composting can efficiently treat the solid manure fraction. Experiments at a pilot scale level with the solid fraction of hen manure showed that various amendments (peat, straw, sawdust) could be used for the production of composts having an elevated NPK content, reduced levels of Clostridia and faecal coliforms, vital weed seeds and the absence of Salmonella and helminth eggs.

One- and two-stage upflow anaerobic sludge-bed reactor pretreatment of winery wastewater at 4–10°C

The operating performance of a single and two (in series) laboratory upflow anaerobic sludge-bed (UASB) reactors (2.7-L working volume, recycle ratio varied from 1:1 to 1:18) treating diluted wine vinasse was investigated under psychrophilic conditions (4–10°C). For a single UASB reactor seeded with granular sludge, the average organic loading rates (OLRs) applied were 4.7, 3.7, and 1.7 g of chemical oxygen demand (COD)/(L·d) (hydraulic retention times [HRTs] were about 1 d) at 9–11, 6 to 7, and 4 to 5°C, respectively. The average total COD removal for preacidified vinasse wastewater was about 60% for all the temperature regimes tested. For two UASB reactors in series, the average total COD removal for treatment of non-preacidified wastewater exceeded 70% (the average OLRs for a whole system were 2.2, 1.8, and 1.3 g of COD/[L·d] under HRTs of 2 d at 10, 7, and 4°C, respectively). In situ determinations of kinetic sludge characteristics (apparent Vm and Km) revealed the existence of substantial mass transfer limitations for the soluble substrates inside the reactor sludge bed. Therefore, application of higher recycle ratios is essential for enhancement of UASB pretreatment under psychrophilic conditions. The produced anaerobic effluents were shown to be efficiently posttreated aerobically: final effluent COD concentrations were about 0.1 g/L. Successful operation of the UASB reactors at quite low temperatures (4–10°C) opens some perspectives for application of high-rate anaerobic pretreatment at ambient temperatures.

Combined biologic (anaerobic-aerobic) and chemical treatment of starch industry wastewater

A combined biologic and chemical treatment of high-strength (total chemical oxygen demand [CODtot] up to 20 g/L), strong nitrogenous (total N up to 1 g/L), and phosphoric (total P up to 0.4 g/L) starch industry wastewater was investigated at laboratory-scale level. As a principal step for COD elimination, upflow anaerobic sludge bed reactor performance was investigated at 30°C. Under hydraulic retention times (HRTs) of about 1 d, when the organic loading rates were higher than 15g of COD/(L·d), the CODtot removal varied between 77 and 93%, giving effluents with a COD/N ratio of 4–5∶1, approaching the requirements of subsequent denitrification. The activated sludge reactor operating in aerobic-anoxic regime (HRT of about 4 d, duration of aerobic and anoxic phases of 30 min each) was able to remove up to 90% of total nitrogen and up to 64% of CODtot from the anaerobic effluents under 17–20°C. The coagulation experiments with Fe(III) showed that 1.4 mg of resting hardly biodegradable COD and 0.5 mg of phosphate (as P) could be removed from the aerobic effluents by each milligram of iron added.

The UASB Treatment of Winery Wastewater under Submesophilic and Psychrophilic Conditions

The start-up and operational performance of two laboratory UASB reactors (working volume of 2.6 l) treating diluted vinasse (1-17 g COD l−1) were investigated at 35 °C (run 1, without recycle), 19-21°C (run 2, without recycle), 18-20°C (run 3, with recycle 1:1) and 9-10 °C (run 4, with recycle 1:2.6). The reactors for runs 1 and 2 were seeded with flocculant mesophilic sludge. For runs 3 and 4, the reactor seed sludge was upgraded by addition of 30% of psychrotrophically adapted granular sludge. A successful start-up of the reactors for all runs was achieved in 2-3 months. The maximum applied organic loading rates (OLR) were 15.9, 6.5, 12.5 and 7.2 g CODl−1d−1 for runs 1-4, respectively. Hydraulic retention times at these loadings were around or less than 1 day. The total COD removals achieved under these OLR were higher than 85% for the first 3 runs and higher than 60% for run 4 with substantial decoloration of effluents (reduction of polyphenol content varied between 45-67%).

Anaerobic toxicity and biodegradability of hydrolysis products of chemical warfare agents.

The toxicity and biodegradability of the main hydrolysis products of chemical warfare agents were investigated under methanogenic conditions. Among the tested substances, only MPhA does not have any toxic effect with regard to the aceticlastic methanogenic activity. The toxicity of other compounds varied between moderate (TDG, mercaptoethanol) to strong (ethanolamine, diisobutyl ester of MPhA). Biodegradability tests showed that all the products of chemical detoxification of mustard gas (ethanolamine, ethylene glycol, TDG, mercaptoethanol) can be biomineralized under methanogenic conditions. On the contrary, phosphorus-containing compounds from the chemical detoxification of nerve warfare agents (Sarin, Soman, Vx-gases) are quite persistent under these conditions.

Sustainable treatment and reuse of diluted pig manure streams in Russia: from laboratory trials to full-scale implementation.

This article summarizes the results obtained during the laboratory and pilot development of integrated biologic and physicochemical treatment and reuse of diluted pig manure streams. The application of a straw filter was an effective means to separate the solid and liquid fractions of raw wastewater and resulted in the removal of a significant part of the dry matter, total nitrogen, and phosphorus (65, 27, and 32%, respectively). From the filtrate generated, 60–80% of the total chemical oxygen demand (COD) was removed in an upflow anaerobic sludge bed reactor operating at 15–30°C. Ammonia was efficiently eliminated (>99%) from the anaerobic effluents using Ural laumantite as an ion exchanger. However, the nitrogen-content of the zeolite was too low to consider this method of ammonia removal economically feasible. The phosphate precipitation block, consisting of stripper of CO2 and fluidized-bed crystallizator, was able to decrease the concentration of soluble phosphate in the anaerobic effluents up to 7–15 mg of phosphate/L. The application of aerobic/anoxic biofilter as a sole polishing step was acceptable from an aesthetic point of view (the effluents were transparent and almost colorless and odorless) and elimination of biochemical oxygen demand (the resting COD was hardly biodegradable). However, the effluent nutrient concentrations (especially nitrogen) were far from the current standards for direct discharge of treated wastewater. We discuss the approaches for further improvement of effluent quality. Finally, we provide an outline of a full-scale system that partially implements the laboratory- and pilot-scale results obtained.

Biosensors based on a light-addressable potentiometric sensor (LAPS) for analysis in both aqueous solutions and organic solvents

Characteristics of a light-addressable potentiometric sensor (LAPS) based on silicon with Ta2O5 dielectric are reported. The pH sensitivity obtained is 45 mV/pH unit in the pH range from 4.01 to 7.5 (for measurements conducted in citrate buffer solutions) and 55 mV/pH unit over the pH range from 7.5 to 8.9 (for measurements conducted in Tris-HCl buffer solutions). The kinetic characteristics (Km3Vm5 pH-profile) of different enzymes, i.e., glucose oxidase, α-chymotrypsin, butyrylcholin esterase, and urease, have been measured under homogeneous conditions. The values of the Michaelis constant obtained are very close to analogous data described in the literature. Biosensors were prepared by immobilization of the enzymes on a pH-sensitive matrix. Two methods of immobilization were used: incorporation in to a hydrophilic matrix of bovine serum albumin (BSA) and incorporation into a hydrophobic matrix of modified polyethylenimine (PEl). It is demonstrated that LAPS can be used for recording the enzymatic reactions in organic media (mixture of the solvents).

Investigation of Kinetic and Microbiological Features of UASB-Reactor Performance Under Various Organic Loading Rates

Kinetic and microbiological features of the performance of a laboratory UASB-reactor fed with synthetic wastewater were investigated under the increase of organic loading rates (OLR) in the range from 3.41 to 45.1 g COD l−1 day−1 with detailed monitoring of the fed substrates and process intermediates, pH, TSS, VSS, specific biomass activities (acidogenic, acetoclastic, litotrophic) as well as distribution of number of the different groups of microorganisms through the reactor height. The optimal conditions for active granular biomass formation under the regimes investigated were found and the general regularities of the process were determined.For a stable UASB-reactor operation, overall average active biomass should not be less than 25 g VVS l−1. In the sludge bed zone, this concentration should be higher than 60 g VVS l−1 After changing the operating regime, the reactor should be maintained at new regime not less than 10–15 HRT. The increase of OLR should be made stepwise; passage to the next regime should be performed after achievement of quasi-steady-state on the previous regime with maximal possible organic matter conversion. Besides, in the operation of a technology using high flow rate UASB-reactors, special attention should be paid to the efficiency of retention of very active biomass circulating in the sludge blanket zone.