Development and optimisation of VFA driven DEAMOX process for treatment of strong nitrogenous anaerobic effluents

The recently proposed DEAMOX (DEnitrifying AMmonium OXidation) process combines the anammox reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. This paper firstly presents a feasibility study of the DEAMOX process using synthetic (ammonia + nitrate) wastewater where sulphide is replaced by volatile fatty acids (VFA) as a more widespread electron donor for partial denitrification. Under the influent N-NH+4/N-NO3(-) and COD/N-NO3(-) ratios of 1 and 2.3, respectively, the typical efficiencies of ammonia removal were around 40% (no matter whether a VFA mixture or only acetate were used) for nitrogen loading rates (NLR) up to 1236 mg N/l/d. This parameter increased to 80% by increasing the influent COD/N-NO3(-) ratio to 3.48 and decreasing the influent N-NH4 +/N-NO3(-) ratio to 0.29. As a result, the total nitrogen removal increased to 95%. The proposed process was further tested with typical strong nitrogenous effluent such as reject water (total N, 530-566 mg N/l; total COD, 1530-1780 mg/l) after thermophilic sludge anaerobic digestion. For this, the raw wastewater was split and partially ( approximately 50%) fed to a nitrifying reactor (to generate nitrate) and the remaining part ( approximately 50%) was directed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance up to NLR of 1,243 mg N/l/d in the DEAMOX reactor was achieved resulting in 40, 100, and 66% removal of ammonia, NOx(-), and total nitrogen, respectively.

Energy potential of anaerobic digestion of solid wastes generated in the Russian Federation

The well known use of the microbiological process of anaerobic digestion (AD) to generate biogas (mixture of methane and carbon dioxide) is now widely implemented for the production of renewable energy worldwide. In Russia, however, this is not the case despite huge amounts of solid organic wastes (SOW) suitable for AD. This paper firstly inventories major flows of SOW from various sectors of the national economy (agriculture, industry, households etc) and estimates their biogas potential. Special attention is put on existing bottlenecks and barriers to implementation of biogas technology given the Russian socio-economic conditions.

Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics

A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using one-dimensional (with regard to reactor height) equations. A universal description of both the fluid hydrodynamics and granular sludge dynamics was elaborated by applying known physical laws and empirical relations derived from experimental observations. In addition, the developed model includes: (1) multiple-reaction stoichiometry, (2) microbial growth kinetics, (3) equilibrium chemistry in the liquid phase, (4) major solid-liquid-gas interactions, and (5) material balances for dissolved and solid components along the reactor height. The integrated model has been validated with a set of experimental data on the start-up, operation performance, sludge dynamics, and solute intermediate concentration profiles of a UASB reactor treating cheese whey [Yan et al. (1989) Biol Wastes 27:289-305; Yan et al. (1993) Biotechnol Bioeng 41:700-706]. A sensitivity analysis of the model, performed with regard to the seed sludge characteristics and the key model parameters, showed that the output of the dispersed plug flow model was most influenced by the sludge settleability characteristics and the growth properties (especially mu(m)) of both protein-degrading bacteria and acetotrophic methanogens.

Application of biopreparation "Rhoder" for remediation of oil polluted polar marshy wetlands in Komi Republic

This paper describes the testing and corresponding results of the preparation "Rhoder" in comparison with several other bioremediation variants during the field trials in Komi Republic throughout 2002-2003. All bioremediation trials were performed on one vast polar marshy wetland polluted by accidental crude oil spill and uncovered by grass. After application of the "Rhoder" at the site, with an area of approximately 2000 m(2), during the cold and rainy summer of 2002 (1.5 months), the level of oil contamination decreased by 20-51%, depending on initial oil pollution (458-738 g/kg dry weight of soil). In the middle of September 2002, the treated site was covered by 70-85% with green grass. Though, during 2003, the "Rhoder" treatment was not practiced, at the end of August 2003, the site was already covered by 85-95% with green grass and the level of oil contamination further decreased by 54-79% from the initial level of oil pollution at the beginning of 2002. These results were much better compared to those from other bioremediation variants applied at this spill.

Sequenced anaerobic-aerobic treatment of high strength, strong nitrogenous landfill leachates

As a first step in treatment of high strength, strong nitrogenous landfill leachates (total COD--9.66-20.56 g/l, total nitrogen 780-1,080 mg/l), the performance of laboratory UASB reactors has been investigated under sub-mesophilic (19+/-3 degrees C) and psychrophilic (10+/-2 degrees C) conditions. Under hydraulic retention time (HRT) of around 1.2 days, when the average organic loading rate (OLR) was around 8.5 g COD/l/day, the total COD removal accounted for 71% (on average) for sub-mesophilic regime. The psychrophilic treatment conducted under the average HRT of 2.44 days and the average OLR of 4.2 g COD/l/day showed an average total COD removal of 58% giving effluents more suitable for subsequent biological nitrogen removal. Both anaerobic regimes were quite efficient for elimination of heavy metals by concomitant precipitation in the form of insoluble sulphides inside the sludge. The subsequent submesophilic aerobic-anoxic treatment of submesophilic anaerobic effluents led to only 75% of total inorganic N removal due to COD deficiency for denitrification created by too efficient anaerobic step. On the contrary, psychrophilic anaerobic effluents (richer in COD compared to the submesophilic ones) were more suitable for subsequent aerobic-anoxic treatment giving the total N removal of 95 and 92% at 19 and 10 degrees C, respectively.

Adaptation of Pseudomonas fluorescens to Al-Citrate: Involvement of Tricarboxylic Acid and Glyoxylate Cycle Enzymes and the Influence of Phosphate

The degradation of Aluminum-citrate by Pseudomonas fluorescens necessitated a major restructuring of the various enzymatic activities involved in the TCA and glyoxylate cycles. While a six-fold increase in fumarase (FUM EC 4.2.1.2) activity was observed in cells subjected to Al-citrate compared to control cells, citrate synthase (CS EC 4.1.3.7) activity experienced a two-fold increase. On the other hand, in the Al-stressed cells malate synthase (MS EC 4.1.3.2) activity underwent a five-fold decrease in activity. This modulation of enzymatic activities appeared to be evoked by Al stress, as the incubation of Al-stressed cells in control media led to the complete reversal of these enzymatic profiles. These observations were further confirmed by 1H NMR and 13C NMR spectroscopy. No significant variations were observed in the activities of other glyoxylate and TCA cycle enzymes, like isocitrate lyase (ICL EC 4.1.3.1), malate dehydrogenase (MDH EC 1.1.1.37), and succinate dehydrogenase (SDH EC 1.3.99.1). This reconfiguration of the metabolic pathway appears to favour the production of a citrate-rich aluminophore that is involved in the sequestration of Al.

The IWA Anaerobic Digestion Model No 1 (ADM1)

The IWA Anaerobic Digestion Modelling Task Group was established in 1997 at the 8th World Congress on Anaerobic Digestion (Sendai, Japan) with the goal of developing a generalised anaerobic digestion model. The structured model includes multiple steps describing biochemical as well as physicochemical processes. The biochemical steps include disintegration from homogeneous particulates to carbohydrates, proteins and lipids; extracellular hydrolysis of these particulate substrates to sugars, amino acids, and long chain fatty acids (LCFA), respectively; acidogenesis from sugars and amino acids to volatile fatty acids (VFAs) and hydrogen; acetogenesis of LCFA and VFAs to acetate; and separate methanogenesis steps from acetate and hydrogen/CO2. The physico-chemical equations describe ion association and dissociation, and gas-liquid transfer. Implemented as a differential and algebraic equation (DAE) set, there are 26 dynamic state concentration variables, and 8 implicit algebraic variables per reactor vessel or element. Implemented as differential equations (DE) only, there are 32 dynamic concentration state variables.

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

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 degreesC). 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 degreesC, 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 degreesC, 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 degreesC) opens some perspectives for application of high-rate anaerobic pretreatment at ambient temperatures.

Psychrophilic one- and two-step systems for pre-treatment of winery waste water

The operation performance of a single and two (in series) laboratory UASB reactors (working volume of 2.7 l, recycle ratio varied from 1:1 to 1:18) treating diluted wine vinasse was investigated under psychrophilic conditions (4-10 degrees C). For a single UASB reactor seeded with granular sludge, the average organic loading rates (OLR) applied were 4.7, 3.7 and 1.7 g COD/l/d (hydraulic retention times (HRTs) were around 1 d) at 9-11, 6-7 and 4-5 degrees C, respectively. The average total COD removal for preacidified vinasse wastewater was around 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 COD/l/d under HRTs of 2 days at 10, 7 and 4 degrees C, respectively). In situ determinations of kinetic sludge characteristics (Vm and Km) revealed the existence of substantial mass-transfer limitations for the soluble substrates inside the reactor sludge bed. Therefore an application of higher recycle rations is essential for enhancement of UASB pre-treatment under psychrophilic conditions. The produced anaerobic effluents were shown to be efficiently post-treated aerobically--final effluent COD concentrations were around 0.1 g/l.

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.

Purification and properties of Clostridium thermocellum endoglucanase 5 produced in Escherichia coli

Endoglucanase 5 (EG5) has been isolated from the strain of E. coli TG1 harboring recombinant plasmid pCU108, which contains the cel5 gene of C. thermocellum. The enzyme has been produced with 98-fold purification and a final yield of 27% by using subsequent twofold high performance ion-exchange chromatography on Mono Q and high performance chromatofocusing on Mono P. The protein has a mol mass of 35 kDa and includes 3 multiple forms with pI 4.4-4.8 as evidenced by analytical gel isoelectrofocusing. EG5 cleaves CMC (Km = 0.097 g/L, Vmax = 8.2 mg/min.mg of protein), amorphous cellulose, xylan, lichenan as a substrate with an optimum temperature of 80 degrees C and pH 6.0 and Avicel (Km = 18.2 g/L, Vmax = 0.035 mg/min.mg of protein) with an optimum temperature of 60 degrees C and pH 6.0. Cellobiose in concentrations up to 200 micrograms/mL do not inhibit the hydrolysis of CMC by EG5, but 10-30 micrograms/mL of glucose significantly decrease the activity of this enzyme. The stimulating role of calcium chloride and concentration of protein in the system has been demonstrated for Avicel hydrolysis by EG5.