Evaluation of a static granular bed reactor using a chemical oxygen demand balance and mathematical modeling

In order to evaluate the static granular bed reactor (SGBR), a chemical oxygen demand (COD) balance was used along with a mathematical model. The SGBR was operated with an organic loading rate (OLR) ranging from 0.8 to 5.5 kg/m³ day at 24 °C. The average COD removal efficiency was 87.4%, and the removal efficiencies of COD, carbohydrates, and proteins increased with an OLR, while the lipids removal efficiency was not a function of an OLR. From the results of the COD balance, the yield of biomass increased with an OLR. The SGBR was modeled using the general transport equation considering advection, diffusion, and degradation by microorganisms, and the first-order reaction rate constant was 0.0166/day. The simulation results were in excellent agreement with experimental data. In addition, the SGBR model provided mechanistic insight into why the COD removal efficiency in the SGBR is proportional to an OLR.     

Performance and spatial community succession of an anaerobic baffled reactor treating acetone-butanol-ethanol fermentation wastewater

An anaerobic baffled reactor with four compartments (C1-C4) was successfully used for treatment of acetone-butanol-ethanol fermentation wastewater and methane production. The chemical oxygen demand (COD) removal efficiency was 88.2% with a CH₄ yield of 0.25 L/(g COD_removed) when organic loading rate (OLR) was 5.4 kg COD m⁻³ d⁻¹. C1 played the most important role in solvents (acetone, butanol and ethanol) and COD removal. Community structure of C2 was similar to that in C1 at stage 3 with higher OLR, but was similar to those in C3 and C4 at stages 1-2 with lower OLR. This community variation in C2 was consistent with its increased role in COD and solvent removal at stage 3. During community succession from C1 to C4 at stage 3, abundance of Firmicutes (especially OTUs ABRB07 and ABRB10) and Methanoculleus decreased, while Bacteroidetes and Methanocorpusculum became dominant. Thus, ABRB07 coupled with Methanoculleus and/or acetogen (ABRB10) may be key species for solvents degradation.     

The treatment of cheese whey wastewater by sequential anaerobic and aerobic steps in a single digester at pilot scale

The treatment of reconstituted whey wastewater was performed in a 400 L digester at 20 °C, with an anaerobic digestion step, followed by a step of aerobic treatment at low oxygen concentration in the same digester. In a first set of 48 cycles, total cycle time (T_C) of 2, 3 and 4 days were tested at varying organic loading rates (OLR). The COD removal reached 89 ± 4, 97 ± 3 and 98 ± 2% at T_C of 2, 3 and 4 days and OLR of 0.56, 1.04 and 0.78 gCOD L⁻¹ d⁻¹, respectively. The activity of the biomass decreased for the methanogenic population, while increasing by 400% for the acidogens, demonstrating a displacement in the predominant trophic group in the biomass bed. A second set of 16 cycles was performed with higher soluble oxygen concentration in the bulk liquid (0.5 mg L⁻¹) during the aerobic treatment at a T_C of 2 days and an OLR of 1.55 gCOD L⁻¹ d⁻¹, with a soluble COD removal of 88 ± 3%. The biomass specific activities showed a compartmentalization of the trophic group with methanogenic activity maintained in the biomass bed and a high acidogenic activity in the suspended flocs.     

Influence of carbohydrates and proteins concentration on fermentative hydrogen production using canteen based waste under acidophilic microenvironment

Functional role of biomolecules viz., carbohydrates and proteins on acidogenic biohydrogen (H₂) production was studied through the treatment of canteen based composite food waste. The performance was evaluated in an anaerobic sequencing batch reactor (AnSBR) at pH 6 with five variable organic loading conditions (OLR1, 0.854; OLR2, 1.69; OLR3, 3.38; OLR4, 6.54 and OLR5, 9.85 kg COD/m³-day). Experimental data depicted the feasibility of H₂ production from the stabilization of food waste and was found to depend on the substrate load. Among the five loading conditions studied, OLR4 documented maximum H₂ production (69.95 mmol), while higher substrate degradation (3.99 kg COD/m³-day) was observed with OLR5. Specific hydrogen yield (SHY) vary with the removal of different biomolecules and was found to decrease with increase in the OLR. Maximum SHY was observed with hexose removal at OLR1 (139.24 mol/kg Hexose_R at 24 h), followed by pentoses (OLR1, 108.26 mol/kg Pentose_R at 48 h), proteins (OLR1, 109.71 mol/kg Protein_R at 48 h) and total carbohydrates (OLR1, 58.31 mol/kg CHO_R at 24 h). Proteins present in wastewater helped to maintain the buffering capacity but also enhanced the H₂ production by supplying readily available organic nitrogen to the consortia. Along with carbohydrates and proteins, total solids also registered good removal.     

Treatment of poultry slaughterhouse wastewater in hybrid upflow anaerobic sludge blanket reactor packed with pleated poly vinyl chloride rings

In this study, the performance of 5.4 L hybrid upflow anaerobic sludge blanket (HUASB) reactor for treating poultry slaughterhouse wastewater under mesophilic conditions (29-35 °C), was investigated. After starting-up, the reactor was loaded up to an OLR of 19 kg COD/m³ d and achieved varied TCOD and SCOD removal efficiencies of 70-86% and 80-92%, respectively. The biogas was varied between 1.1 and 5.2 m³/m³ d with the maximum methane content of 72%. The maximum methane yield was 0.32 m³/kg COD_removed at an OLR of 9.27 kg COD/m³ d. Black matured granules of size between 2.5 and 5 mm were observed at the end of 225 d operation. RTD study showed the flow behavior was in mixed regime at the end of performance study. Step wise polynomial regression analysis was fitted well. Methanobacterium and Methanosaeta bacteria were dominant at the end of start-up whereas Methanosarcina, Cocci and rods were predominant at the end of performance studies.     

Two stage anaerobic baffled reactors for bio-hydrogen production from municipal food waste

A two-step anaerobic baffled reactor (ABR-1 and ABR-2) for H₂ production from municipal food waste (MFW) was investigated at a temperature of 26 °C. In ABR-1, the average yield of H₂ at an HRT of 26 h and OLR of 58 kg COD/m³ d was 250 ml H₂/g VS removed. As unexpected; the H₂ production in the ABR-2 was further increased up to 370 ml H₂/gVS removed at a HRT of 26 h and OLR of 35 kgCOD/m³ d. The total H₂ yield in the two-step process was estimated to be 4.9 mol H₂/mol hexose. The major part of H₂ production in the ABR-1 was due to the conversion of COD_particulate (36%). In the ABR-2 the H₂ yield was mainly due to the conversion of COD in the soluble form (76%). Based on these results MFW could be ideal substrate for H₂ production in a two-step ABR processes.     

Bio-kinetic analysis on treatment of textile dye wastewater using anaerobic batch reactor

An anaerobic digestion technique was applied to textile dye wastewater aiming at the colour and COD removal. Pet bottles of 5 L capacity were used as reactor which contains methanogenic sludge of half a liter capacity which was used for the treatment of combined synthetic textile dye and starch wastewater at different mixing ratios of 20:80, 30:70, 40:60, 50:50 and 60:40 with initial COD concentrations as 3520, 3440, 3360, 3264 and 3144 mg L⁻¹, respectively. The reactor was maintained at room temperature (30 ± 3 °C) with initial pH of 7. The maximum COD and colour removal were 81.0% and 87.3% at an optimum mixing ratio of 30:70 of textile dye and starch wastewaters. Both Monod’s and Haldane’s models were adopted in this study. The kinetic constants of cell growth under Haldane’s model were satisfactory when compared to Monod’s model. The kinetic constants obtained by Haldane’s model were found to be in the range of μ_max = 0.037-0.146 h⁻¹, K_s = 651.04-1372.88 mg L⁻¹ and K_i = 5681.81-18727.59 mg L⁻¹.     

Seasonal effects of 19 plant species on COD removal in subsurface treatment wetland microcosms

Plants have many well-documented influences in treatment wetlands, but differences in individual species’ effects on year-round and seasonal performance are poorly understood. In this study, we evaluated plant effects on seasonal patterns of organic carbon removal (measured as COD) and sulfate concentration (used as an indicator of rootzone oxidation) in replicated, batch-loaded, greenhouse microcosms simulating subsurface treatment wetlands. Microcosms were planted with monocultures of 19 plant species or left unplanted as controls, dosed every 20 days with synthetic secondary wastewater, and operated over 20 months at temperatures from 4 to 24 °C. Study-long COD removal averaged 70% for controls and 70-97% for individual species. Most species enhanced COD removal significantly and the benefits of plants were greatest at 4-8 °C because COD removal decreased at low temperatures in controls but displayed limited seasonal variation in planted microcosms. Removal was significantly better at 24 °C than 4 °C with two species (Panicum virgatum and Leymus cinereus), significantly poorer with two species (Carex utriculata and Phalaris arundinacea), and did not differ with 15 species. Only one species showed a significant positive correlation between temperature and COD removal (Iris missouriensis, r = 0.67), while two species showed significant negative correlations (better when colder: Carex nebrascensis, r = −0.67; C. utriculata, r = −0.93). High COD removal throughout the study was strongly associated with high SO₄ concentrations at low temperatures, suggesting that plant performance is related to rootzone oxidation and species’ abilities to promote aerobic over anaerobic microbial processes, particularly in winter. Results indicate that improved year-round and cold-season COD removal is common across diverse wetland plant species and novel species can be as good or better than those typically used. Better performing species were largely in the sedge and rush families (Cyperaceae and Juncaceae), while poorer performing species were largely in the grass family (Poaceae).     

Effect of seed sludge and operation conditions on performance and archaeal community structure of low-temperature anaerobic solvent-degrading bioreactors

Two laboratory-scale expanded granular sludge bed (EGSB) anaerobic bioreactors (R1 and R2) were inoculated with biomass from different mesophilic (37 °C) treatment plants, and used for the treatment of an organic solvent-based wastewater at 9–14 °C at applied organic loading rates (OLRs) of 1.2–3.6 kg chemical oxygen demand (COD) m⁻³ d⁻¹. Replicated treatment performance was observed at 10–14 °C, which suggested the feasibility of the process at pilot-scale. Stable and efficient COD removal, along with high methane productivity, was demonstrated at 9 °C at an applied OLR of 2.4 kg COD m⁻³ d⁻¹. Clonal libraries and fluorescence in situ hybridization (FISH) indicated that the seed sludges were dominated (>60%) by acetoclastic Methanosaeta-like organisms. Specific methanogenic activity (SMA) profiles indicated shifts in the physiological profiles of R1 and R2 biomass, including the development of psychrotolerant methanogenic activity. Acetoclastic methanogenesis represented the primary route of methane production in R1 and R2, which is in contrast with several previous reports from low-temperature bioreactor trials. A reduction in the abundance of Methanosaeta-like clones (R2), along with the detection of hydrogenotrophic methanogenic species, coincided with altered granule (sludge) morphology and the development of hydrogenotrophic SMA after prolonged operation at 9 °C.     

Effect of organic loading rate on VFA production, organic matter removal and microbial activity of a two-stage thermophilic anaerobic membrane bioreactor

This study focused on the VFA (volatile fatty acid) profile variation with organic loading rate (OLR) of a two stage thermophilic anaerobic membrane bioreactor (TAnMBR). The two stage TAnMBR treating high strength molasses-based synthetic wastewater was operated under a side-stream partial sedimentation mode at 55 °C. Reactor performances were studied at different OLR ranging from 5 to 12 kg COD m⁻³ d⁻¹. Operational performance of TAnMBR was monitored by assessing biological activity, organic removal efficiency, and VFA. The major intermediate products of anaerobic digestion were identified as acetate, propionate, iso-butyrate, n-butyrate and valerate. Among them acetate and n-butyrate were identified as the most abundant components. Increase of OLR changes the predominant VFA type from acetic acid to n-butyric acid and the total VFA concentration was increased with increased OLR. Moreover, increased OLR increased organic removal efficiency up to second loading rate and dropped in third loading rate while biological activity was increased continuously.     

A glucose-tolerant β-glucosidase from Prunus domestica seeds: Purification and characterization

A glucose-tolerant β-glucosidase was purified to homogeneity from prune (Prunus domestica) seeds by successive ammonium sulfate precipitation, hydrophobic interaction chromatography and anion-exchange chromatography. The molecular mass of the enzyme was estimated to be 61 kDa by SDS-PAGE and 54 kDa by gel permeation chromatography. The enzyme has a pI of 5.0 by isoelectric focusing and an optimum activity at pH 5.5 and 55 °C. It is stable at temperatures up to 45 °C and in a broad pH range. Its activity was completely inhibited by 5 mM of Ag⁺ and Hg²⁺. The enzyme hydrolyzed both p-nitrophenyl β-d-glucopyranoside with a K_m of 3.09 mM and a V_max of 122.1 μmol/min mg and p-nitrophenyl β-d-fucopyranoside with a K_m of 1.65 mM and a V_max of 217.6 μmol/min mg, while cellobiose was not a substrate. Glucono-δ-lactone and glucose competitively inhibited the enzyme with K_i values of 0.033 and 468 mM, respectively.     

Laboratory scale examination of the effects of overloading on the anaerobic digestion by glycerol

The anaerobic digestion of pure glycerol, which produces a baseline acetic acid to propionic acid ratio of 0.2, was studied in laboratory scale reactors (3 l working volume) at mesophilic temperature (37 °C) with 3000 mg chemical oxygen demand (COD) l⁻¹d⁻¹. During the experiment tVFA and C2-C6 VFA analysis and daily biogas yield measurement were carried out. Following 10 days of a 15% d⁻¹ increase in the organic loading rate (OLR) of 3.0-10.5 g COD l⁻¹d⁻¹, the concentration of propionic acid increased to 6200-8000 mg l⁻¹. Then the inoculum was divided into three parts feeding with 100% glycerol, 50% glycerol + 50% acetic acid, and 50% glycerol + 50% thick stillage, (presented in % of 2.60 g COD l⁻¹d⁻¹ OLR), respectively. The application of co-substrates reduced the recovery period by 5 days compared to feeding with pure glycerol. When the reactors were loaded with glycerol again (10% OLR raise per day) the previously applied co-substrates had a positive effect on the VFA composition and the biogas yield as well.     

Purification and characterisation of a bifunctional alginate lyase from novel Isoptericola halotolerans CGMCC 5336

A novel halophilic alginate-degrading microorganism was isolated from rotten seaweed and identified as Isoptericola halotolerans CGMCC5336. The lyase from the strain was purified to homogeneity by combining of ammonium sulfate fractionation and anion-exchange chromatography with a specific activity of 8409.19 U/ml and a recovery of 25.07%. This enzyme was a monomer with a molecular mass of approximately 28 kDa. The optimal temperature and pH were 50 °C and pH 7.0, respectively. The lyase maintained stability at neutral pH (7.0–8.0) and temperatures below 50 °C. Metal ions including Na⁺, Mg²⁺, Mn²⁺, and Ca²⁺ notably increased the activity of the enzyme. With sodium alginate as the substrate, the K_m and V_max were 0.26 mg/ml and 1.31 mg/ml min, respectively. The alginate lyase had substrate specificity for polyguluronate and polymannuronate units in alginate molecules, indicating its bifunctionality. These excellent characteristics demonstrated the potential applications in alginate oligosaccharides production with low polymerisation degrees.     

Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

A new sponge tray bioreactor in primary treated sewage effluent treatment

The new attached growth sponge tray bioreactor (STB) was evaluated at different operating conditions for removing organics and nutrients from primary treated sewage effluent. This STB was also assessed when using as a pre-treatment prior to micro-filtration (MF) for reducing membrane fouling. At a short hydraulic retention time (HRT) of 40 min, the STB could remove up to 92% of DOC and 40-56% of T-N and T-P at an organic loading rate (OLR) of 2.4 kg COD/m³ sponge day. This OLR is the best for the STB as compared to the OLRs of 0.6, 1.2 and 3.6 kg COD/m³ sponge day. At 28 mL/min of flow velocity (FV), STB achieved the highest efficiencies with 92% of DOC, 87.4% of T-P, and 54.8% of T-N removal. Finally, at the optimal OLR and FV, the STB could remove almost 90% of organic and nutrient, significantly reduce membrane fouling with HRT of only 120 min.     

Treatment of fresh leachate with high-strength organics and calcium from municipal solid waste incineration plant using UASB reactor

Treatment of a fresh leachate with high-strength organics and calcium from municipal solid waste (MSW) incineration plant by an up-flow anaerobic sludge blanket (UASB) reactor was investigated under mesophilic conditions, emphasizing the influence of organic loading rate (OLR). When the reactor was fed with the raw leachate (COD as high as 70,390-75,480 mg/L) at an OLR of 12.5 kg COD/(m³ d), up to ∼82.4% of COD was removed suggesting the feasibility of UASB process for treating fresh leachates from incineration plants. The ratio of volatile solids/total solids (VS/TS) of the anaerobic sludge in the UASB decreased significantly after a long-term operation due to the precipitation of calcium carbonate in the granules. Scanning electron microscopy (SEM) observation shows that Methanosaeta-like species were in abundance, accompanied by a variety of other species. The result was further confirmed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing.     

Biochemical characterization of a 27 kDa 1,3-β-d-glucanase from Trichoderma asperellum induced by cell wall of Rhizoctonia solani

Trichoderma asperellum produces two extracellular 1,3-β-d-glucanase upon induction with cell walls from Rhizoctonia solani. A minor 1,3-β-d-glucanase was purified to homogeneity by ion exchange chromatography on Q-Sepharose and gel filtration on Sephacryl S-100. A typical procedure provided 13.8-fold purification with 70% yield. SDS-PAGE of the purified enzyme showed a single protein band of molecular weight 27 kDa. The enzyme exhibited optimum catalytic activity at pH 3.6 and 45 °C. It was thermostable at 40 °C, and retained 75% activity after 60 min at 45 °C. The K_m and V_max values for 1,3-β-d-glucanase, using laminarin as substrate, were 0.323 mg ml⁻¹ and 0.315 U min⁻¹, respectively. The enzyme was strongly inhibited by Hg²⁺ and SDS. The enzyme was only active toward glucans containing β-1,3-linkages. Peptide sequences showed similarity with two endo-1,3(4)-β-d-glucanases from Aspergillus fumigatus Af293when compared against GenBank non-redundant database.     

Effect of chitosan on UASB treating POME during a transition from mesophilic to thermophilic conditions

The effects of chitosan addition on treatment of palm oil mill effluent were investigated using two lab-scale upflow anaerobic sludge bed (UASB) reactors: (1) with chitosan addition at the dosage of 2 mg chitosan per g volatile suspended solids on the first day of the operation (R1), (2) without chitosan addition (the control, R2). The reactors were inoculated with mesophilic anaerobic sludge which was acclimatized to a thermophilic condition with a stepwise temperature increase of 5 °C from 37 to 57 °C. The OLR ranged from 2.23 to 9.47 kg COD m⁻³ day⁻¹. The difference in biogas production rate increased from non-significant to 18% different. The effluent volatile suspended solids of R1 was 65 mg l⁻¹ lower than that of R2 on Day 123. 16S rRNA targeted denaturing gradient gel electrophoresis (DGGE) fingerprints of microbial community indicated that some methanogens in the genus Methanosaeta can be detected in R1 but not in R2.     

Evaluation of an on-site pilot static granular bed reactor (SGBR) for the treatment of slaughterhouse wastewater

An on-site pilot-scale static granular bed reactor (SGBR) system was evaluated for treating wastewater from a slaughterhouse in Iowa. The study evaluated SGBR reactor suitability for slaughterhose wastewater having high particulate COD concentration (7.9 ± 4.3 g COD/L) at 0.3–1.4 m³/m²/day of the surface loading rates. High organic removal efficiency (over 95% of TSS and VSS removal) was obtained due to the consistent treatability of SGBR system during operation at HRTs of 48, 36, 30, 24, and 20 h. The average effluent TSS, VSS, COD, soluble COD, and BOD₅ concentrations were 84, 71, 301,197, and 87 mg/L, respectively. An effective backwash procedure was performed once every 7–14 days to waste a portion of the accumulated solids in the system. This procedure limited the increase in hydraulic head loss and maintained the system stability. COD removal efficiencies greater than 95% were achieved at organic loading rates ranging from 0.77 to 12.76 kg/m³/day.