The effect of various iron hydroxide concentrations on the anaerobic fermentation of sulfate-containing model sewage

The addition of iron hydroxide and iron-reducing bacteria into a fermenter for anaerobic processing of sulfate-containing sewage was shown to decrease sulfate reduction and sulfide concentration, while increasing the total organic carbon (TOC) and methane production. The effect of iron (III) in sulfate-containing sewage depended on its dose, which can be expressed as molar ratio Fe(III)/SO4(2-). Sulfide concentration increased monotonically, reaching 91 mg/l and 45 mg/l after 15 days of processing at Fe(III)/SO4(2-) ratios of 0.06 and 0.5, respectively. However, soluble sulfide production was not observed at ratios equaling 1 and 2. At ratios of 0.06, 0.5, 1, and 2, the maximum rates of TOC removal were 0.75, 1.15, 1.39, and 1.55 g TOC/g of organic matter (OM) per 1 h. Methane production rates were 0.039, 0.047, 0.064, and 0.069 mg/g OM per 1 h, with the mean relative amounts of methane in the biogas being equal to 25, 41, 55, and 62%, respectively. These data can be applied to the development of new methods of anaerobic purification of sulfate-containing sewage.     

Supplementation with non-fibrous carbohydrates reduced fiber digestibility and did not improve microbial protein synthesis in sheep fed fresh forage of two nutritive values

To determine whether non-fibrous carbohydrate (NFC) supplementation improves fiber digestibility and microbial protein synthesis, 18 Corriedale ewes with a fixed intake level (40 g dry matter (DM)/kg BW0.75) were assigned to three (n = 6) diets: F = 100% fresh temperate forage, FG = 70% forage + 30% barley grain and FGM = 70% forage + 15% barley grain + 15% molasses-based product (MBP, Kalori 3000). Two experimental periods were carried out, with late (P1) and early (P2) vegetative stage forage. For P2, ewes were fitted with ruminal catheters. Forage was distributed at 0900 h, 1300 h, 1800 h and 2300 h, and supplement added at 0900 h and 1800 h meals. Digestibility of the different components of the diets, retained N and rumen microbial protein synthesis were determined. At the end of P2, ruminal pH and N-NH3 concentration were determined hourly for 24 h. Supplementation increased digestibility of DM (P < 0.001) and organic matter (OM; P < 0.001) and reduced NDF digestibility (P = 0.043) in both periods, with greater values in P2 (P = 0.008) for the three diets. Daily mean ruminal pH differed (P < 0.05) among treatments: 6.33 (F), 6.15 (FG) and 6.51 (FGM). The high pH in FGM was attributed to Ca(OH)2 in MBP. Therefore, the decreased fiber digestibility in supplemented diets could not be attributed to pH changes. The mean ruminal concentration of N-NH3 was 18.0 mg/dl, without differences among treatments or sampling hours. Microbial protein synthesis was greater in P2 (8.0 g/day) than in P1 (6.1 g/day; P = 0.006), but treatments did not enhance this parameter. The efficiency of protein synthesis tended to be lower in supplemented groups (16.4, 13.9 and 13.4 in P1, and 20.8, 16.7 and 16.2 g N/kg digestible OM ingested in P2, for F, FG and FGM, respectively; P = 0.07) without differences between supplements. The same tendency was observed for retained N: 2.55, 1.38 and 1.98 in P1, and 2.28, 1.23 and 1.10 g/day in P2, for F, FG and FGM, respectively; P = 0.05). The efficiency of microbial protein synthesis was greater in P2 (P = 0.007). In conclusion, addition of feeds containing NFCs to fresh temperate forage reduced the digestibility of cell walls and did not improve microbial protein synthesis or its efficiency. An increase in these parameters was associated to the early phenological stage of the forage.     

Treatment of recycled wastewaters from fishmeal factory by an anaerobic filter

Fishmeal industries processes produce effluents with high load organic matter. These effluents, after recycling and physical-chemical pretreatment, have a high organic content (5-6 g COD/l), proteins (3-5 g/l), salinity close to sea water, sodium chloride (30 g/l) and sulphate (1-3.3 g/l). An anaerobic filter was used for the treatment of this wastewater, with marine sediment as anaerobic inoculum. Anaerobic filter removed up to 70% of the influent COD concentrations at organic loading rates (OLR) of 9.5 and 14.3 (g/l d) and sulphate up to 80% at OLR of 7.1 and 14.3 (g/l d) whereas the pH ranged between 7.0 and 7.5. These results show that anaerobic filter systems are applicable to recycled wastewaters from fishmeal.     

Isolation of an aboriginal bacterial community capable of utilizing cyanide, thiocyanate, and ammonia from metallurgical plant wastewater

An aboriginal bacterial community capable of degrading cyanide (10 mg/l) and thiocyanate (2 g/l) and eliminating ammonia (120 mg/l) had been isolated from recycled water samples after blast-furnace gas purification of a metallurgical plant wastewater. It was shown that the optimal conditions for this bacterial community were as follows: temperature, 34 degrees C; pH, 8.8-9.0; available organic matter concentration (glucose equivalent), 5 g/l; and dissolved O2 concentration, 8-10 mg/l. This aboriginal community was formed by the bacteria belonging to the genus Pseudomonas.     

Characteristics of the bioreactor landfill system using an anaerobic-aerobic process for nitrogen removal

A sequential upflow anaerobic sludge blanket (UASB) and air-lift loop sludge blanket (ALSB) treatment was introduced into leachate recirculation to remove organic matter and ammonia from leachate in a lab-scale bioreactor landfill. The results showed that the sequential anaerobic-aerobic process might remove above 90% of COD and near to 100% of NH4+ -N from leachate under the optimum organic loading rate (OLR). The total COD removal efficiency was over 98% as the OLR increased to 6.8-7.7 g/l d, but the effluent COD concentration increased to 2.9-4.8 g/l in the UASB reactor, which inhibited the activity of nitrifying bacteria in the subsequent ALSB reactor. The NO3- -N concentration in recycled leachate reached 270 mg/l after treatment by the sequential anaerobic-aerobic process, but the landfill reactor could efficiently denitrify the nitrate. After 56 days operation, the leachate TN and NH4+ -N concentrations decreased to less than 200 mg/l in the bioreactor landfill system. The COD concentration was about 200 mg/l with less than 8 mg/l BOD in recycled leachate at the late stage. In addition, it was found that nitrate in recycled leachate had a negative effect on waste decomposition.     

Comparison of composting, storage and urea treatment for sanitising of faecal matter and manure

To close the loop of nutrients in a safe way, the loop of pathogens has to be broken. By sanitising organic fertilisers derived from faeces and manure, the first step in the disease transmission chain is broken. Two alternatives for this treatment, thermophilic composting and ammonia-based treatment, were evaluated and compared to storage treatment. Thermal composting of faecal matter and food waste resulted in a treatment temperature of over 65 degrees C in a 90 L reactor. By using insulation and turning the compost three times during the high temperature period, it is possible to ensure a 5 log(10) reduction of pathogens. Small scale composting of the same material indicated less efficient reduction of faecal bacteria at temperatures around 50 degrees C. In the chemical treatment tested, an addition of 3% N-NH(3) increased the pH to above 9 within 1h and resulted in a good reduction in the indicator organisms for bacteria (Salmonella spp. and faecal coliforms D(r)<0.7 days, Enterococcus spp. D(r)<3 days). Lower addition rates resulted in a longer treatment period needed. The storage period tested resulted in slow reduction of faecal coliforms, Salmonella spp. and Enterococcus spp.     

Gradients of coastal fish farm effluents and their effect on coral reef microbes

Coastal milkfish (Chanos chanos) farming may be a source of organic matter enrichment for coral reefs in Bolinao, Republic of the Philippines. Interactions among microbial communities associated with the water column, corals and milkfish feces can provide insight into the ecosystem's response to enrichment. Samples were collected at sites along a transect that extended from suspended milkfish pens into the coral reef. Water was characterized by steep gradients in the concentrations of dissolved organic carbon (70-160 microM), total dissolved nitrogen (7-40 microM), chlorophyll a (0.25-10 microg l(-1)), particulate matter (106-832 microg l(-1)), bacteria (5 x 10(5)-1 x 10(6) cells ml(-1)) and viruses (1-7 x 10(7) ml(-1)) that correlated with distance from the fish cages. Particle-attached bacteria, which were observed by scanning laser confocal microscopy, increased across the gradient from < 0.1% to 5.6% of total bacteria at the fish pens. Analyses of 16S rRNA genes by denaturing gradient gel electrophoresis and environmental clone libraries revealed distinct microbial communities for each sample type. Coral libraries had the greatest number of phyla represented (range: 6-8) while fish feces contained the lowest number (3). Coral libraries also had the greatest number of 'novel' sequences (defined as < 93% similar to any sequence in the NCBI nt database; 29% compared with 3% and 5% in the feces and seawater libraries respectively). Despite the differences in microbial community composition, some 16S rRNA sequences co-occurred across sample types including Acinetobacter sp. and Ralstonia sp. Such patterns raise the question of whether bacteria might be transported from the fish pens to corals or if microenvironments at the fish pens and on the corals select for the same phylotypes. Understanding the underlying mechanisms of effluent-coral interactions will help predict the ability of coral reef ecosystems to resist and rebound from organic matter enrichment.     

Nitrate Regeneration Coupled to Degradation of Different Size Fractions of DON by the Picoplankton in the Elbe Estuary

Bacterial conversion of high (HMW > 3,000 Da) and low (LMW < 3,000 Da) molecular weight DON (dissolved organic nitrogen) was studied along the freshwater section of the Elbe estuary during the summer of 1997. Indigenous populations of picoplankton were incubated in a flow-through chamber that allowed a constant exchange of sterile, filtered Elbe water as the culture medium for the microorganisms, which remained within the chamber. Nitrogen conversion was followed by changes in the concentrations of total and low molecular weight DON and dissolved inorganic nitrogen compounds, the uptake of O2, and bacterial growth. Along the Elbe estuary, total DON concentrations varied between 0.69 and 1.1 mg N L-1, of which between 64 and 79% was LMW-DON. Ammonium was a minor nutrient present in the Elbe at concentrations below 0.26 mg N L-1. During incubation in the laboratory between 27 and 64% of the LMW-DON was consumed at rates ranging from 24 to 51 g N L-1 h-1. HMW-DON was used only when the degradable LMW-DON pool became exhausted and accounted for between 60 and 100% of the HMW-DON. This produced an increase in the DON consumption rate between 43 and 79 g N L-1 h-1. Nitrification rates were independent of the external ammonium concentration until it decreased to below 1 g N-NH4 L-1. Most of the N in the nitrification process originated as NH4 regenerated from DON. Between 75 and 100% of the LMW-DON and ammonium consumed was rapidly converted to nitrate. This amount decreased to between 65 and 85% when HMW-DON was consumed in addition to the LMW-DON. DON and ammonium consumption supported nitrification rates up to 71 g N L-1 h-1. The amount of DOC (dissolved organic carbon) degraded was not equivalent to the C:N ratio of the total dissolved organic matter. Calculations based on oxygen consumption for respiration and ammonium regeneration revealed that the substrates used during the incubations contained C:N at ratios of about 3:1. These results suggest that the nitrogen-rich compounds had been removed from the dissolved organic matter and subsequently consumed by bacteria, while the carbon skeleton remained mostly unaffected by the degradation processes.     

Neutralization/recovery of lactic acid from Lactococcus lactis: effects on biomass,lactic acid,and nisin production

Besides lactic acid, many lactic acid bacteria also produce proteinaceous metabolites (bacteriocins) such as nisin. As catabolite repression and end-product inhibition limit production of both products, we have investigated the use of alternative methods of supplying substrate and neutralizing or extracting lactic acid to increase yields. Fed-batch fermentation trials using a stillage-based medium with pH control by NH4OH resulted in improved lactic acid (83.4 g/l, 3.18 g/l/h, 95% yield) and nisin (1,260 IU/ml, 84,000 IU/l/h, 14,900 IU/g) production. Removing particulate matter from the stillage-based medium increased nisin production (1,590 IU/ml, 33,700 IU/g), but decreased lactic acid production (58.5 g/l, 1.40 g/l/h, 96% yield). Removing lactic acid by ion exchange resins stimulated higher lactic acid concentrations (60 to 65 g/l) and productivities (2.0 to 2.6 g/l/h) in the filtered stillage medium at the expense of nisin production (1,500 IU/ml, 25,800 IU/g).     

Interactions between organic and inorganic carbon sources during mixotrophic cultivation of Synechococcus sp.

Glucose at 3 g l(-1) markedly accelerated growth of Synechococcus sp. PCC 7002. The net photosynthesis rate was 263 micromol O2 (mg Chl a h)(-1) for mixotrophic culture and 146 micromol O2 (mg Chl a h)(-1) for photoautotrophic culture. Additing 1 g NaHCO3 l(-1) to the glucose-supplemented culture enhanced the photosynthetic rate by 18%, and the total carbon consumption rate was raised to 2.5 mg l(-1) (mg chl a h)(-1) from a previously negative value. An interaction between organic and inorganic carbon metabolism was established.     

Biotransformation of phosphogypsum in media containing different forms of nitrogen

Studies on the biotransformation of phosphogypsum (a waste product formed in the course of the production of phosphorous fertilizers) with the use of sulfate reducing bacteria (SRB) demonstrated that it is a good source of sulfates and biogenic elements for these bacteria, though the addition of organic carbon and nitrogen is necessary. The aim of this study was to investigate the form of nitrogen and C:N ratio in the medium on the growth of SRB community in cultures containing phosphogypsum. Batch community cultures of sulfate reducing bacteria were maintained in medium with phosphogypsum (5.0 g/l), different concentrations of sodium lactate (1.6 - 9.4 g/l) and different forms (NH4CI, CO(NH2)2, KNO3) and concentrations (0 - 250 mg/l) of nitrogen. The growth of SRB was studied in the C:N ratio of from 2:1 to 300:1. It was found that: 1 - the best source of nitrogen for SRB is urea, followed by ammonium, the worst were nitrates; 2 - the bacteria were also able to grow in medium without nitrogen but their activity was then by approximately 15% lower than in optimal growth conditions; 3 - in medium with KNO3 inhibition of sulfate reduction by approx. 50% was observed; 4 - the highest reduction of nitrates (removal of nitrate) in media with phosphogypsum and nitrates was at limiting concentrations of sodium lactate. This is probably caused by the selection under these conditions (low concentration of hydrogen sulfide) of denitrifying bacteria or sulfate reducing bacteria capable of using nitrates as an electron acceptor.     

Degradation of carbazole in the presence of non-aqueous phase liquids by Pseudomonas sp.

Biodegradation of carbazole was enhanced by the presence of a non-aqueous phase liquid (logKo/w > or = 3.1) at phase ratio of 1:1 (organic/aqueous). In a cyclohexane/aqueous phase system, the maximum specific degradation rate (3.34 mg carbazole min(-1) g dry cell(-1)) was at an organic/aqueous ratio of 1:1. Pseudomonas sp. XLDN4-9 degraded 47% (w/w) of 1 g carbazole l(-1) in cyclohexane phase directly within 1 h.     

Development of a carrier for adhesion of nitrifying bacteria using a thermodynamic approach

Biopop, a novel modified cellulose carrier for nitrification was developed through thermodynamic analysis of carrier materials. By measuring contact angles among nitrifying bacteria, solid carrier and broth, the change in free energy of adhesion of nitrifying bacteria on carrier (G) was calculated. Cellulose gave the most favorable free energy change for adhesion of nitrifying bacteria and all the inoculated microbes were attached on porous carrier made of cellulose within 1 day. The new carrier gave a nitrification rate (800 g N-NH /m day), which was about four times higher than other carriers made of synthetic polymers such as polyurethane or rubber.     

Thermophilic (55 degrees C) conversion of methanol in methanogenic-UASB reactors: influence of sulphate on methanol degradation and competition

Two upflow sludge bed reactors (UASB) were operated for 80 days at 55 degrees C with methanol as the substrate with an organic loading rate (OLR) of about 20 g CODl(-1) per day and a hydraulic retention time (HRT) of 10 h. One UASB was operated without sulphate addition (control reactor-R1) whereas the second was fed with sulphate at a COD:SO4(2-) ratio of 10 (sulphate-fed reactor-R2), providing an influent sulphate concentration of 0.6 g l(-1). For both reactors, methanogenesis was the dominant process with no considerable accumulation of acetate. The methanol removal averaged 93% and 83% for R1 and R2, respectively, and total sulphate removal was achieved in the latter. The pathway of methanol conversion for both sludges was investigated by measuring the fate of carbon in the presence and absence of bicarbonate or specific inhibitors for a sludge sample collected at day 72. In both sludges, about 70% of the methanol was syntrophically converted to methane and/or sulphide, via the intermediate H2/CO2. A strong competition between methanogens and sulphidogens took place in the R2 sludge with half of the methanol-COD being used by methane-producing bacteria and the other half by sulphate-reducing bacteria. Acetate was not an important intermediate for both sludges, and played a slightly more important role for the sulphate-adapted sludge (R2), sustained by the higher amount of bicarbonate produced during sulphate-reduction. The pathway study indicates that, although acetate does not represent an important intermediate, the system is susceptible to its accumulation.     

Isolation of an aboriginal bacterial community capable of utilizing cyanide,thiocyanate, and ammonia from metallurgical plant wastewater

An aboriginal bacterial community capable of degrading cyanide (10 mg/l) and thiocyanate (2 g/l) and eliminating ammonia (120 mg/l) had been isolated from recycled water samples after blast-furnace gas purification of a metallurgical plant wastewater. It was shown that the optimal conditions for this bacterial community were as follows: temperature, 34°C; pH, 8.8–9.0; available organic matter concentration (glucose equivalent), 5 g/l; and dissolved O₂ concentration, 8–10 mg/l. This aboriginal community was formed by the bacteria belonging to the genus Pseudomonas.     

Effect of mixed organic substrate on α-tocopherol production by <Emphasis Type="Italic">Euglena gracilis</Emphasis> in photoheterotrophic culture

Effects of organic carbon sources on cell growth and alpha-tocopherol productivity in wild and chloroplast-deficient W14ZUL strains of Euglena gracilis under photoheterotrophic culture were investigated. In both strains, the increase in cell growth was particularly high when glucose was added as the sole organic carbon source. On the other hand, alpha-tocopherol production per dry cell weight was enhanced by adding ethanol. Ethanol addition also increased the chlorophyll concentration in wild strain and mitochondria activity in W14ZUL strain. For effective alpha-tocopherol production, the effects of mixture of glucose and ethanol were investigated. The results showed that, when a mixture of glucose (6 g/l) and ethanol (4 g/l) was used, alpha-tocopherol productivity per culture broth was 3.89 x 10(-2) mg l(-1) h(-1), which was higher than the value obtained without addition of organic carbon source (0.92 x 10(-2) mg l(-1) h(-1)). In addition, under fed-batch cultivation using an internally illuminated photobioreactor, the alpha-tocopherol production per culture broth was 23.43 mg/l, giving a productivity of 16.27 x 10(-2) mg l(-1) h(-1).     

Methane fermentation of coastal mud sediment by a two-stage upflow anaerobic sludge blanket (UASB) reactor system

The removal of organic matter from a coastal mud sediment was carried out by a methane fermentation process under anaerobic conditions. In a batch acidogenic fermentation, the addition of vitamins containing thiamine, nicotinic acid and biotin dramatically enhanced acetate production from the mud sediment (200 g wet wt l(-1) artificial sea water), yielding 77 mM acetate after 6 days, which corresponded to 77% of the organic matter in the mud sediment, measured on the basis of chemical oxygen demand. Thereafter, the two-fold diluted, post-acidogenic fermentation liquor (PAF liquor) was continuously treated at 2.4x original dilution rate day(-1) for 30 days, using an upflow anaerobic sludge blanket methanogenic reactor containing the acclimated methanogenic sludge from the mud sediment. Acetate, 42 mM in the PAF liquor, was converted to methane at a maximum methane production rate of 96 mmol l(-1) day(-1); and 87.5% of the acetate and 88.7% of the total organic carbon in the PAF liquor were removed. Moreover, an efficient treatment of the mud sediment was carried out by a semi-continuous, two-stage reactor system, where the culture broth was circulated between acidogenic and methanogenic reactors. This two-stage reactor system gave a stable operation at 4-day intervals for one treatment period, yielding 112 mmol methane from the wet mud in the PAF liquor (278 g l(-1)).     

Feeding ecology of the freshwater detritivore Ptychoptera paludosa (Diptera, Nematocera)

1. We examined selected aspects of the nutritional ecology of larval Ptychoptera paludosa and their role in nutrient cycling in the Breitenbach, a first-order stream in Hesse, Germany.
2. Food preference experiments demonstrated significant preference for sediments with a high organic matter content and live bacteria.
3. pH was circumneutral in all sections of the gut.
4. Enzymatic activity (β-glucosidase and amino-peptidase) in different parts of the gut was measured using 4-methylumbelliferyl-β- D -glucopyranoside (MUF-Glc) and leucine-4-methylcoumarinyl-7-amide (Leu-MCA). β-glucosidase activity was highest in the hindgut.
5. The mean larval gut passage time was between 7 and 8 h.
6. The egestion rate of last instar larvae was about 0.35 mg dry weight (DW) faeces per larva h^–1 and about 1.25 mg ash-free dry weight (AFDW) faeces per mg larval AFDW day^–1.
7. Larval faeces contained at least 4–18 times more organic matter than the average in the sediments in which they were feeding, that is, larvae fed selectively, extracting organic matter from sediments.
8. P. paludosa larvae are important in the dynamics of detritus in slow-flowing reaches of the Breitenbach. They gather organic material from the sediment to a depth of 3 cm, and release it as faeces onto the sediment surface. A total of 770 g DW faeces m^–2 yr^–1, comprising about 16% organic matter, was produced by the Ptychoptera population.     

Synthesis of bacteriochlorophyll a by the purple nonsulfur bacterium Rhodobacter capsulatus

The ability of purple nonsulfur bacteria Rhodobacter capsulatus B10 to synthesize bacteriochlorophyll under phototrophic and dark conditions was studied. The modes for cultivation in the dark with oxygen limitation in a continuous culture at D = 0.1 h(-1) were selected. The yield of biomass reached 20 g/l; the bacteriochlorophyll a output of the process amounted to 16.6 mg/l h(-1).     

The effect of various iron hydroxide concentrations on the anaerobic fermentation of sulfate-containing model wastewater

The addition of iron hydroxide and iron-reducing bacteria into a reactor for anaerobic processing of sulfate-containing wastewater was shown to decrease sulfate reduction and sulfide concentration, while increasing the total organic carbon (TOC) and methane production. The effect of iron (III) in sulfate-containing wastewater depended on its dose, which can be expressed as molar ratio Fe(III)/SO ₄ ^2? . Sulfide concentration increased monotonically, reaching 91 and 45 mg/l after 15 days of processing at Fe(III)/SO ₄ ^2? ratios of 0.06 and 0.5, respectively. However, soluble sulfide production was not observed at ratios equaling 1 and 2. At ratios of 0.06, 0.5, 1, and 2, the maximum rates of TOC removal were 0.75, 1.15, 1.39, and 1.55 g TOC/g of organic matter (OM) per 1 h. Methane production rates were 0.039, 0.047, 0.064, and 0.069 ml/g OM per 1 h, with the mean relative amounts of methane in the biogas being equal to 25, 41, 55, and 62%, respectively. These data can be applied to the development of new methods of anaerobic purification of sulfate-containing wastewater.