Halophila ovalis (R. Br.) Hook. f. from a submarine hot spring in southern Japan

Colonies of the seagrass Halophila ovalis are found growing adjacent to coral Acropora sp. and Seriatopora hystrix in a submarine hot spring (at 15.7 m depth, 28.6°C) at the north coast of Taketomi Island, near the southern tip of Japan. Halophila plants grow in sea water containing sulphide 930 μg S ml⁻¹ and on the substratum with fine precipitates of the submarine hot spring which have sulphide content up to 5400 μg S g⁻¹ DW. The accumulated sulphide concentration reaches as high as 8400 μg S g⁻¹ DW in under ground tissues and 5700 μg S g⁻¹ DW in above-ground tissues, respectively. It is suggested that, not the sulphide concentration but light and possibly water temperature are the limiting factors for the Halophila colonization in the submarine hot spring.     

Oxidation of hydrogen sulphide in sour gas by Chlorobium limicola

The aim of this work was to assess the potential for bacterial oxidation of hydrogen sulphide as a purification method of sour gas. Using a continuous culture of Chlorobium limicola, high efficiencies of oxidation of both soluble and gaseous sulphide were achieved, with efficiencies for the latter exceeding 95%. Sulphide added as aqueous sodium sulphide was converted to sulphur and sulphate with almost total removal of the initial 100 mg S l⁻¹ within 24 h. Gaseous sulphide was oxidized at an efficiency of 95% (approximately 3 mmol S h⁻¹ (unit biomass Abs)⁻¹) over 1 h runs at a gas flow rate of 60 ml min⁻¹. With a sulphur recovery system to prevent sulphur accumulation, an efficiency of 70% was maintained. Biological removal of sulphide represents a potentially important biotechnological process, with high potential for viable scale up.     

Phenol inhibition of biological nutrient removal in a four-step sequencing batch reactor

Nutrient removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different phenol (C₆H₅OH) concentrations in order to determine the inhibition effects of phenol on biological nutrient removal. The nutrient removal process consisted of anaerobic, oxic, anoxic, and oxic phases with hydraulic residence times (HRT) of 1 h/3 h/1 h/1 h and a settling phase of 3/4 h. Solids retention time (SRT) was kept constant at 10 days in all experiments. Initial phenol concentrations were varied between 0 and 600 mg l⁻¹ at seven different levels. The effects of phenol on COD, NH₄-N, and PO₄-P removals and effluent nutrient levels were investigated. Phenol was almost completely degraded up to 400 mg l⁻¹ phenol concentration resulting in almost negligible inhibition effects on COD, NH₄-N, and PO₄-P removals. Nutrient removals were adversely affected by phenol at concentrations above 400 mg l⁻¹. Above 95% COD, 90% NH₄-N and 65% PO₄-P removal was obtained for phenol concentrations below 400 mg l⁻¹. The sludge volume index (SVI) was almost constant around 45 ml g⁻¹ for phenol concentrations below 400 mg l⁻¹ but increased to 90 ml g⁻¹ at a phenol level of 600 mg l⁻¹.     

Performance of anaerobic baffled reactor (ABR) treating synthetic wastewater containing p-nitrophenol

In this study, the effect of increasing p-nitrophenol (PNP) concentrations on the performance of anaerobic baffled reactor (ABR) (chemical oxygen demand (COD), removals, volatile fatty acid (VFA), p-aminophenol (PAP) and methane gas productions) was investigated through 240 days. The PNP concentrations were raised to 700 from 10 mg/L corresponding to PNP loading rates of 0.97 and 67.9 g/m³ day. The PNP and COD removal efficiencies were 99 and 90% at PNP loading rates as high as 33.9 g/m³ day, respectively, through the acclimation of anaerobic granular sludge. After this loading rate, the removal efficiencies decreased to 79%. The COD removal efficiencies were high in compartment 1 (E = 78–93%) while a small amount of COD removal was achieved in compartments 2 and 3. The PNP removal efficiencies were approximately 90% in all PNP loading rates except for loading rate of 0.97 g/m³ day. The maximum PNP removal efficiency was measured as 99% at a loading rate of 8.32 g/m³ day. The optimum PNP loading rate for maximum COD, PNP removals and methane yield was 8.32 g/m³ day. The total, methane gas productions and methane percentages were approximately 2160–2400 mL/day and 950–1250 mL/day and 44–52% for the PNP loading rates varying between 4.36 and 33.9 g/m³ day, respectively. For PNP loading rates varying between 33.9 and 67.9 g/m³ day, the total, methane gas productions and methane percentages were approximately 2160 and 960 mL/day and 44%, respectively. The highest total volatile fatty acid (TVFA) concentrations were found in the first compartment with fluctuated values varied between 50 and 200 mg/L indicating the acidogenesis. p-Aminophenol was found as the main intermediate through anaerobic degradation of PNP which later was broken down to phenol and ammonia.     

Determination of kinetic constants of hybrid textile wastewater treatment system

The present study is related to treatment of textile wastewater in microaerophilic–aerobic hybrid reactor. The study showed the effectiveness of biological treatment of wastewater involving appropriate microorganism and suitable reactors. COD and color were reduced to 82–94%, and 99% respectively for textile wastewater. The reactor was operated at highest loading of 16.4 g COD g l⁻¹ d⁻¹ and obtained 80% COD and 72% color removal. Biokinetic models were applied to data obtained from experimental studies in continuously operated hybrid reactor. Treatment efficiencies of the reactor were investigated at different hydraulic retention times (2.3–9.1 d) and organic loading rates (2.6–16.4 g COD l⁻¹ d⁻¹). Second-order and a Stover–Kincannon models were best fitted to the hybrid column reactor. The second-order substrate removal rate constant (k_2(S)) was found as 41.44 d⁻¹ for hybrid reactor. Applying the modified Stover–Kincannon model to the hybrid reactor, the maximum removal rate constant (U_max) and saturation value constant (K_B) were found to be 212 g l⁻¹ d⁻¹ and 22.89 g l⁻¹ d⁻¹, respectively.     

Biological phosphorus removal in sequencing batch reactor with single-stage oxic process

The performance of biological phosphorus removal (BPR) in a sequencing batch reactor (SBR) with single-stage oxic process was investigated using simulated municipal wastewater. The experimental results showed that BPR could be achieved in a SBR without anaerobic phase, which was conventionally considered as a key phase for BPR. Phosphorus (P) concentration 0.22–1.79 mg L⁻¹ in effluent can be obtained after 4 h aeration when P concentration in influent was about 15–20 mg L⁻¹, the dissolved oxygen (DO) was controlled at 3 ± 0.2 mg L⁻¹ during aerobic phase and pH was maintained 7 ± 0.1, which indicated the efficiencies of P removal were achieved 90% above. Experimental results also showed that P was mainly stored in the form of intracellular storage of polyphosphate (poly-P), and about 207.235 mg phosphates have been removed by the discharge of rich-phosphorus sludge for each SBR cycle. However, the energy storage poly-β-hydroxyalkanoates (PHA) was almost kept constant at a low level (5–6 mg L⁻¹) during the process. Those results showed that phosphate could be transformed to poly-P with single-stage oxic process without PHA accumulation, and BPR could be realized in net phosphate removal.     

The effect of pretreatment on anaerobic activity of olive mill wastewater using batch and continuous systems

This study was focused on several physico-chemical and biological treatment methods that may affect the reduction of the organic load in olive mill wastewater (OMW). In this study, removal of 95% of the phenolic compounds present in OMW was achieved using sand filtration and subsequent treatment with powdered activated carbon in a batch system. This pretreatment for OMW was found to enhance the anaerobic activity of the sludge in the batch system significantly. The efficiency of organic load removal achieved by the anaerobic treatment of untreated OMW in batch reactors with tap water dilution factors below 1:10, reached approximately 65% chemical oxygen demand (COD) removal. However, in the up-flow sludge anaerobic blanket (UASB) reactor, COD removal efficiency of 80–85% was reached at a hydraulic retention time (HRT) of 5 days with an influent COD concentration of 40 g l⁻¹ and organic loading rate (OLR)=8 g⁻¹ COD l⁻¹ per day.     

Cadmium biosorption on Spirulina platensis biomass

Dry biomass of Spirulina platensis re-hydrated for 48 h was employed as a biosorbent in tests of cadmium(II) removal from water. Various concentrations of biomass (from 1 to 4 g l⁻¹) and metal (from 100 to 800 mg l⁻¹) were tested. Low biomass levels (X_o  2 g l⁻¹) ensured metal removal up to 98% only at Cd₀= 100 and 200 mg l⁻¹, while X_o  2.0 g l⁻¹ were needed at Cd₀ = 400 mg l⁻¹ to achieve satisfactory results. Whereas X_o = 4.0 g l⁻¹ was effective to remove up to Cd₀ = 500 mg l⁻¹, a further increase in metal concentration (Cd₀ = 600 and 800 mg l⁻¹) led to progressive worsening of the system performance. At a given biomass levels, the kinetics of the process was better at low Cd²⁺ concentrations, while, raising the adsorbent level from 1.0 to 2.0 g l⁻¹ and then to 4.0 g l⁻¹, the rate constant of biosorption increased by about one order of magnitude in both cases and the adsorption capacity of the system progressively decreased from 357 to 149 mg g⁻¹.     

A packed-bed fungal bioreactor for the continuous decolourisation of azo-dyes (Orange II)

The degradation of an azo dye, Orange II, by immobilised Phanerochaete chrysosporium in a continuous packed bed bioreactor for periods longer than 30 days has been carried out. Nearly complete decolourisation (>95%) was achieved when working at a high dye load rate of 0.2 g l⁻¹ d⁻¹, a temperature of 37 °C, a hydraulic retention time (HRT) of 24 h and applying oxygen gas in a pulsed flow. These conditions allowed Manganese peroxidase (MnP) production and the subsequently Orange II decolourisation. A correlation between residual MnP activity in the effluent and decolourisation was established. Apparently, for decolourisation to be effective, a minimum MnP activity was required, no substantial increase in efficiency at MnP activities higher than 10 U 1 ⁻¹ was observed. The treatment caused, the breakdown of the chromophoric group as well as the cleavage of the aromatic ring.     

Effect of redox mediator, AQDS, on the decolourisation of a reactive azo dye containing triazine group in a thermophilic anaerobic EGSB reactor

The feasibility of thermophilic (55 °C) anaerobic treatment applied to colour removal of a triazine contained reactive azo dye was investigated in two 0.53 l expanded granular sludge blanket (EGSB) reactors in parallel at a hydraulic retention time (HRT) of 10 h. Generally, this group of azo dyes shows the lowest decolourisation rates during mesophilic anaerobic treatment. The impact of the redox mediator addition on colour removal rates was also evaluated. Reactive Red 2 (RR2) and anthraquinone-2,6-disulfonate (AQDS) were selected as model compounds for azo dye and redox mediator, respectively. The reactors achieved excellent colour removal efficiencies with a high stability, even when high loading rates of RR2 were applied (2.7 g RR2 l⁻¹ per day). Although AQDS addition at catalytic concentrations improved the decolourisation rates, the impact of AQDS on colour removal was less apparent than expected. Results show that the AQDS-free reactor R2 achieved excellent colour removal rates with efficiencies around 91%, compared with the efficiencies around 95% for the AQDS-supplied reactor R1. Batch experiments confirmed that the decolourisation rates were co-substrate dependent, in which the volatile fatty acids (VFA) mixture was the least efficient co-substrate. The highest decolourisation rate was achieved in the presence of either hydrogen or formate, although the presence of glucose had a significant impact on the colour removal rates.     

Decolorization of reactive dyes by mixed cultures isolated from textile effluent under anaerobic conditions

In the present study mixed cultures that could grew in the molasses media were isolated from textile dye effluent and its decolorization activity was studied in a batch system under anaerobic conditions, in order to determine the optimal conditions required for the highest decolorization activity. The optimum pH value for decolorization was determined as 8 for all the dyes tested. In the experiment with pH 8 dye decolorizations by mixed cultures were investigated at about 96.2–1031.3 mg l⁻¹ initial dye concentrations. The highest dye removal rates of mixed cultures were 94.9% for Reactive Red RB, 91.0% for Reactive Black B and 63.6% for Remazol Blue at 953.2, 864.9 and 1031.3 mg l⁻¹ initial dye concentrations respectively within 24 h incubation period. When the Reactive Red RB was used, approximately 82–98% total color removal was obtained at between 96.2 and 953.2 mg l⁻¹ initial dye concentrations after 12 h of incubation at 35 °C. These results show that our enriched mixed cultures have the potential to serve as an excellent biomass for the use in reactive dye removal from wastewaters under anaerobic conditions.     

Enhanced dye decolorization efficiency by citraconic anhydride-modified horseradish peroxidase

Bromophenol blue and methyl orange removal capabilities of citraconic anhydride-modified horseradish peroxidase were compared with those of native horseradish peroxidase. Citraconic anhydride-modified horseradish peroxidase showed higher decolorization efficiencies for both dyes than native horseradish peroxidase. Upon the chemical modification, the decolorization efficiencies were increased by 1.8% and 12.4% for bromophenol blue and methyl orange, respectively. The quantitative relationships between decolorization efficiencies of dyes and reaction conditions were also investigated. Experimental data revealed that aqueous phase pH, reaction time, temperature, enzyme concentration and ratio of dye and H₂O₂ play a significant role on the dye degradation. Lower dose of citraconic anhydride-modified horseradish peroxidase was required than that of native enzyme for the decolorizations of both dyes to obtain the same decolorization efficiencies. Citraconic anhydride-modified HRP exhibited a good decolorization of dye over a wide range of dye concentration from 8 to 24 or 32 μmol l⁻¹ at 300 μmol l⁻¹ H₂O₂, which would match industrial expectations. Kinetic constants for two different dyes were also determined. Citraconic anhydride-modified horseradish peroxidase shows greater affinity and catalytic efficiency than native horseradish peroxidase for both dyes.     

Bench-scale fermentation of Trichoderma viride on wastewater sludge: Rheology, lytic enzymes and biocontrol activity

Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 10⁷ CFU mL⁻¹ at 96 h) was obtained at 30 g L⁻¹ suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L⁻¹ suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL⁻¹ at 30 g L⁻¹ suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L⁻¹ compared to 30 and 25 g L⁻¹. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, k_La at 35 g L⁻¹ did not increase in comparison to 30 g L⁻¹ due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.     

Human fibroblast culture on a crosslinked dermal porcine collagen matrix

The use of a novel porcine-derived collagen biomaterial as a dermal tissue engineering matrix was examined. The matrix is derived from porcine dermis, and is processed to retain the native collagen (Type 1) and elastin structure. Human primary fibroblasts were cultured on the matrix to examine its potential for creating a dermal replacement. Attachment of fibroblasts on the collagen was compared to tissue culture plastic and PET membranes. Cell proliferation was assessed using the MTT assay and DAPI staining. For seeding densities of 5×10⁴ and 1×10⁵ cells cm⁻², PET and plastic demonstrated >95% attachment of seeded numbers after 3 h. The collagen matrix reached levels >80% after 3–4 h with no influence of the seeding density. Matrix samples with perforating pores of 40 μm diameter were also studied. After 216 h culture in static culture, with media replacement every 3 days, the final cell numbers reached 2.1×10⁵ (perforated) and 2.0×10⁵ cells cm⁻² (unperforated). In comparison fibroblast culture in a perfusion bioreactor, with continuous media replacement, reached 2.3×10⁵ (unperforated) and 2.5×10⁵ cells cm⁻² (perforated) after 216 h.     

Ammonia removal from anaerobically digested dairy manure by struvite precipitation

Ammonia is one of the most important contaminants impairing the quality of water resources. When this is considered along with the fact that the global demand for nitrogenous fertilizers is in constant rise, the need for recovery as well as removal of nitrogen is well justified. Crystallization of N and P in the form of struvite (MgNH₄PO₄·6H₂O), which is a slow releasing and valuable fertilizer, is one possible technique for this purpose. This study investigated the removal of NH₄⁺ through struvite precipitation from the effluents of one- (R1) and two-phase (R2) anaerobic reactors digesting dairy manure. To force the formation of struvite in the anaerobic reactor effluents, Mg²⁺ ion was added by using both Mg(OH)₂ and MgCl₂·6H₂O. To prevent the effect of different total phosphorus (TP) concentration in the effluents of R1 and R2, as well as to not limit the formation of struvite, an excess amount of PO₄³⁻ (0.14 M) was added in the form of Na₂HPO₄. Different stoichiometric Mg²⁺:NH₄⁺:PO₄³⁻ ratios were tested to determine the required Mg²⁺ concentrations for maximum NH₄⁺ removal by keeping NH₄⁺:PO₄³⁻ ratio constant for the effluents of reactors R1 and R2. The results revealed that very high NH₄⁺ removal efficiencies (above 95%) were possible by adding Mg²⁺ ions higher than 0.06 M concentration in the effluents from reactors R1 and R2. It was also observed that the initial pH adjustment to 8.50 using NaOH did not result in any significant increase in the removal of NH₄⁺ and the removal of NH₄⁺ in the reactors treated with MgCl₂·6H₂O was higher than those treated with Mg(OH)₂ for the same Mg²⁺ concentration.     

Kinetics of laccase-catalysed TEMPO oxidation

The oxidation of TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl radical) has been studied in the presence of recombinant laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Polyporus pinsitus (rPpL), Myceliophthora thermophila (rMtL), Coprinus cinereus (rCcL) and Rhizoctonia solani (rRsL) in buffer solution pH 4.5–7.3 and at 25 °C. At pH 5.5 the oxidation constant calculated from the initial rate of TEMPO oxidation was 1.7 × 10⁴, 1.4 × 10³, 7.8 × 10² and 5.2 × 10² M⁻¹ s⁻¹ for rPpL, rRsL, rCcL and rMtL, respectively. The maximal activity of rPpL-catalysed TEMPO oxidation was at pH 5.0. The pK_a obtained in neutral pH range was 6.2. The reactivity of laccases is in a good agreement with laccases copper type I redox potential.

TEMPO oxidation rate increased 541 times in the presence of 10-(3-propylsulfonate) phenoxazine (PSPX). The model of synergistic TEMPO and PSPX oxidation was proposed. Experimentally obtained rate constants for rPpL-catalysed PSPX oxidation were in a good agreement with those calculated from the synergistic model, therefore confirming the feasibility of the model. The acceleration of TEMPO oxidation with high reactive laccase substrates opens new possibilities for TEMPO application as a mediator.     

Removal of lead (Pb(2+)) by the cyanobacterium Gloeocapsa sp

Pb²⁺ removal ability of the viable-freshwater cyanobacterium Gloeocapsa sp. was studied in batch experiments. Gloeocapsa sp. was cultured in the Medium 18 with pH adjusted to 3, 4, 5, 6 and 7. Growth was subsequently determined based on the increase of chlorophyll-a content. Gloeocapsa sp. was able to grow at all pH levels tested, except at pH 3. Removal of Pb²⁺ was then further studied under pH 4. The results showed that Pb²⁺ concentration in the range of 0–20 mg L⁻¹ was not inhibitory to Gloeocapsa sp. growth but reduced its Pb²⁺ removal efficiency (by 4.5% when Pb²⁺ concentration increased from 2.5 to 20 mg L⁻¹). Pb²⁺ removal characteristics followed the Langmuir adsorption isotherm with the maximum removal capacity (q_max) of 232.56 mg g⁻¹. Adsorption of Pb²⁺ by this cyanobacterium followed the second order rate reaction and intraparticle diffusion was likely the rate-determining step. The initial rate of Pb²⁺adsorption during intraparticle diffusion was slower under light than under dark conditions, indicating that light probably slowed down the initial rate of intraparticle diffusion through the repulsion effects on cell membrane.     

Effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater

The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH₄⁺–N l⁻¹ was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N⁻¹ were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased.

The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N⁻¹ while the stoichiometric ratio was 4.2 g COD g N⁻¹. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.     

Effects of feed sugar concentration on continuous ethanol fermentation of cheese whey powder solution (CWP)

Cheese whey powder (CWP) solution with different CWP or sugar concentrations was fermented to ethanol in a continuous fermenter using pure culture of Kluyveromyces marxianus (DSMZ 7239). Sugar concentration of the feed CWP solution varied between 55 and 200 g l⁻¹ while the hydraulic residence time (HRT) was kept constant at 54 h. Ethanol formation, sugar utilization and biomass formation were investigated as functions of the feed sugar concentration. Percent sugar utilization and biomass concentrations decreased and the effluent sugar concentration increased with increasing feed sugar concentrations especially for the feed sugar contents above 100 g l⁻¹. Ethanol concentration and productivity (DP) increased with increasing feed sugar up to 100 g l⁻¹ and then decreased with further increases in the feed sugar content. The highest ethanol concentration (3.7%, v v⁻¹) and productivity (0.54 gE l⁻¹ h⁻¹) were obtained with the feed sugar content of 100 g l⁻¹ or 125 g l⁻¹. The ethanol yield coefficient (Y_P/S) was also maximum (0.49 gE gS⁻¹) when the feed sugar was between 100 and 125 g l⁻¹. The growth yield coefficient (Y_X/S) decreased steadily from 0.123 to 0.063 gX gS⁻¹ when the feed sugar increased from 55 to 200 g l⁻¹ due to adverse effects of high sugar contents on yeast growth. The optimal feed sugar concentration maximizing the ethanol productivity and sugar utilization was between 100 and 125 g l⁻¹ under the specified experimental conditions.     

Nutrient removal by thermophilic Fischerella (Mastigocladus laminosus) in a simulated algaculture process

A novel nutrient removal/waste heat utilization process was simulated using semicontinuous cultures of the thermophilic cyanobacterium Fischerella. Dissolved inorganic carbon (DIC)-enriched cultures, maintained with 10 mg l⁻¹ daily productivity, diurnally varying temperature (from 55°C to 26–28°C), a 12:12 light cycle (200 μE sec⁻¹ m⁻²) and 50% biomass recycling into heated effluent at the beginning of each light period, removed > 95% of NO₃⁻ + NO₂⁻−N, 71% of NH₃-N, 82% of PO₄³⁻ −P, and 70% of total P from effluent water samples containing approximately 400 μg l⁻¹ combined N and 60 μg l⁻¹ P. Nutrient removal was not severely impaired by an altered temperature gradient, doubled light intensity, or DIC limitation. Recycling 75% of the biomass at the end of each light period resulted in unimpaired NO₃⁻ + NO₂⁻ removal, 38–45% P removal and no net NH₃ removal. Diurnally varying P removal, averaging 50–60%, and nearly constant > 80% N removal, are therefore projected for a full-scale process with continuous biomass recycling.