Treatment of phenolics containing synthetic wastewater in an internal loop airlift bioreactor (ILALR) using indigenous mixed strain of Pseudomonas sp. under continuous mode of operation

The scope of this study is to evaluate the performance of internal loop airlift bioreactor (ILALR) in treating synthetic wastewater containing phenol and m-cresol, in single and multi component systems. The microbe utilized in the process was an indigenous mixed strain of Pseudomonas sp. isolated from a wastewater treatment plant. The reactor was operated at both lower and higher hydraulic retention times (HRTs) i.e., 4.1 and 8.3 h, respectively, by providing an inlet feed flow rate of 5 and 10 mL/min. Shock loading experiments were also performed up to a maximum concentration of 800 mg/L for phenol at 8.3 h HRT and 500 mg/L for m-cresol at 4.1 h HRT. The study showed complete degradation of both phenol and m-cresol, when they were degraded individually at a HRT of 8.3 h. Experiments with both phenol and m-cresol present as mixtures were performed based on the 2² full factorial design of experiments.     

Continuous hydrogen and butyric acid fermentation by immobilized Clostridium tyrobutyricum ATCC 25755: Effects of the glucose concentration and hydraulic retention time

The effects of the hydraulic retention time (HRT = 8, 10, 12 or 16.7 h) and glucose concentration (30, 40 or 50 g/L) on the production of hydrogen and butyrate by an immobilized Clostridium tyrobutyricum culture, grown under continuous culturing conditions, were evaluated. With 30 g/L glucose, the higher HRTs tested led to greater butyrate concentrations in the culture, i.e., 9.3 g/L versus 12.9 g/L with HRTs of 8 h and 16.7 h, respectively. In contrast, higher biogas and hydrogen production rates were generally seen when the HRT was lower. Experiments with different glucose concentrations saw a significant amount of glucose washed out when 50 g/L was used, the highest being 22.7 g/L when the HRT was 16.7 h. This study found the best conditions for the continuous production of hydrogen and butyric acid by C. tyrobutyricum to be with an HRT of 12 h and a glucose concentration of 50 g/L, respectively.     

Biohydrogen production in a three-phase fluidized bed bioreactor using sewage sludge immobilized by ethylene–vinyl acetate copolymer

Ethylene–vinyl acetate (EVA) copolymer was used to immobilize H₂-producing sewage sludge for H₂ production in a three-phase fluidized bed reactor (FBR). The FBR with an immobilized cell packing ratio of 10% (v/v) and a liquid recycle rate of 5 l/min (23% bed expansion) was optimal for dark H₂ fermentation. The performance of the FBR reactor fed with sucrose-based synthetic medium was examined under various sucrose concentration (C_so) and hydraulic retention time (HRT). The best volumetric H₂ production rate of 1.80 ± 0.02 H₂ l/h/l occurred at C_so = 40 g COD/l and 2 h HRT, while the optimal H₂ yield (4.26 ± 0.04 mol H₂/mol sucrose) was obtained at C_so = 20 g COD/l and 6 h HRT. The H₂ content in the biogas was stably maintained at 40% or above. The primary soluble metabolites were butyric acid and acetic acid, as both products together accounted for 74–83% of total soluble microbial products formed during dark H₂ fermentation.     

Endozoochory of Mediterranean aquatic plant seeds by teal after a period of desiccation: Determinants of seed survival and influence of retention time on germinability and viability

The capacity of eight wetland seeds to be internally dispersed by common teal (Anas crecca L.) after a dry period typical of natural Mediterranean wetlands was experimentally quantified. These plant taxa (Chara spp., Echinochloacrus-galli (L.) P. Beauv., Eleocharis palustris (L.) Roem. & Schult, Polygonum lapathifolium L., Potamogeton nodosus Poir., Potamogeton pusillus L., Schoenoplectus mucronatus (L.) Palla, Scirpus maritimus L.) were frequently ingested by teal in the field. Captive teal were fed with known quantities of dry seeds and faecal samples were collected at intervals of 1-2 h for 48 h. The proportion of seeds retrieved after gut passage that germinated varied between taxa from 3% to 83%. From 2% to 63% of the seeds ingested were recovered intact, and 18-95% of these were still viable. Therefore, an overall 32% of the seeds ingested were evacuated in a viable condition, ranging from 0.2% for Chara spp. to 54% for S. mucronatus. Mean seed retention time was 3-5 h. Overall, 94% of seeds were evacuated within 12 h, but 2% were recovered after more than 24 h. Seed viability was reduced at longer retention times, although viable seeds of all taxa except Chara spp. were recovered 44-48 h after the experiment began. Germinability was increased by gut passage, although for some species this effect was only significant after stratification, indicating that they exhibit both mechanical and physical dormancy. Seed germination was accelerated by gut passage, especially at longer retention times. Gut passage increased the proportion of viable seeds, suggesting selective digestion of non-viable ones. Endozoochorous transport by teal appears to be a widespread dispersal mechanism among wetland plants.     

Diethyl phthalate degradation by the freeze-dried,entrapped Bacillus subtilis strain 3C3

Microbial degradation is the key treatment for diethyl phthalate (DEP) of which the efficacy is subdued by substrate toxicity. DEP-degrading Bacillus subtilis strain 3C3 adopted cell size alteration as one of the adaptive mechanisms in response to DEP stress at high concentrations. Nevertheless, to enhance cell tolerance in the protected environment and to facilitate practical treatment operation, cell entrapment was optimized with the entrapment yield at 89 ± 1% in a modified minimal salt medium-containing alginate matrix and the freeze-dried, entrapped cells were then formulated. Among several compounds tested, incorporation of sucrose proved to be beneficial as a cryoprotectant sustaining cell biodegradation efficiency (97%) and viability (≥90%) during freeze drying, storage under a vacuum condition at low temperatures, rehydration and as an additional matrix filler to reinforce the bead structure. The effective DEP treatment of the formulated, entrapped cells was demonstrated in a packed bed continuous system in which 70% DEP removal at hydraulic retention time (HRT) of 30 min was occurred and was enhanced up to 90% when HRT was increased to 60 min. The work demonstrates an effective preparation and a potential application of the formulated entrapped DEP-degrading cells for DEP treatment.     

Evaluation of performance and microbial community in a two-stage UASB reactor pretreating acrylic fiber manufacturing wastewater

A two-stage UASB reactor was employed to pretreat acrylic fiber manufacturing wastewater. Mesophilic operation (35 ± 0.5 °C) was performed with hydraulic retention time (HRT) varied between 28 and 40 h. Mixed liquor suspended solids (MLSS) in the reactor was maintained about 8000 mg/L. The results showed COD and sulfate removal could be kept at 51% and 75%, respectively, when the HRT was no less than 38 h. Sulfate reduction mainly occurred in the acidification-stage reactor while methane production mainly occurred in the methane-stage reactor. The size of granule formed in the acidification-stage reactor ranged between 1 and 5 mm while the largest size of granule in the methane-stage reactor ranged from 0.5 to 2 mm. Compared to microbial populations in the acidification-stage reactor, the microbial diversity in methane-stage reactor was more abundant. In the acidification-stage reactor, the Syntrophobacter sulfatireducens devoted to both sulfate reduction and acetate production.     

Effects of initial lactic acid concentration, HRTs, and OLRs on bio-hydrogen production from lactate-type fermentation

A batch test and continuous operation were performed to identify the effect of lactate on hydrogen production at pH 4.5. When the initial lactic acid concentration was increased from 0 to 8 g/L in the batch test, the hydrogen yield also increased from 1.41 to 1.72 mol-H₂/mol-glucose. The system exhibited a long lag time and an insignificant hydrogen yield with 16 g-lactic acid/L. A continuous stirred tank reactor (CSTR) was operated at different organic loading rates (OLRs: 10, 15, 20 and 40 g/L/day) and hydraulic retention times (HRTs: 6, 12 and 24 h). At an OLR of 20 g-glucose/L/day and 12 h of HRT, the hydrogen yield was 1.2 mol-H₂/mol-glucose. The yield decreased with a 24 h HRT. Even though lactate was one of the major constituents of volatile fatty acids (VFAs), hydrogen production was feasible throughout the operation. Clostridium sp. was the dominant hydrogen-producing bacteria in the system.     

Sulfidogenic fluidized bed treatment of real acid mine drainage water

The treatment of real acid mine drainage water (pH 2.7-4.3) containing sulfate (1.5-3.34 g/L) and various metals was studied in an ethanol-fed sulfate-reducing fluidized bed reactor at 35 °C. The robustness of the process was tested by increasing stepwise sulfate, ethanol and metal loading rates and decreasing feed pH and hydraulic retention time. Highest sulfate reduction rate (4.6 g/L day) was obtained with feed sulfate concentration of 2.5 g/L, COD/sulfate ratio of 0.85 and HRT of 12 h. The corresponding sulfate and COD removal efficiencies were about 90% and 80%, respectively. The alkalinity produced in sulfidogenic ethanol oxidation neutralized the acidic mine water. Highest metal precipitation efficiencies were observed at HRT of 24 h, the percent metal removal being over 99.9% for Al (initial concentration 55 mg/L), Co (9.0 mg/L), Cu (49 mg/L), Fe (435 mg/L), Ni (3.8 mg/L), Pb (7.5 mg/L) and Zn (6.6 mg/L), and 94% for Mn (7.21 mg/L).     

Nitrogen removal efficiencies in a free water surface constructed wetland in relation to plant coverage

Vegetation coverage is considered to be a key factor controlling nitrogen removal in wetlands. We describe the use of newly designed stainless steel incubation chambers to detect shifts in the in situ nitrate reduction activities associated to areas covered with common reed (Phragmites australis) and cattail (Typha latifolia) in the sediment of a free water surface constructed wetland (FWS-CW). Activities were measured at six different positions and times of the year and were related to physicochemical and hydraulic variables. Mean nitrate + nitrite reduction activities varied from 11.1 to 69.4 mg N/m²/h and showed a high variability within sediment types. Ammonification rates accounted for roughly 10% of the total nitrate reduction and were especially relevant in vegetated areas. Measured activities were highly above total nitrogen removal efficiencies estimated in the three parallel treatment cells of the Empuriabrava FWS-CW, indicating the potentiality of the system. In situ nitrate reduction activities correlated well with physichochemical characteristics such as pH and temperature. Additionally, differences in the total nitrogen removal efficiencies were detected between the three treatment cells and were related to changes in the water retention time. The plant species effect was detected in treatment cells of comparable hydraulic loads in which vegetation belts dominated by Typha latifolia were shown to have greater nitrogen removal efficiencies.     

Cytotoxicity micropollutant removal in a crossflow membrane bioreactor

The application of membrane bioreactor (MBR) technology was investigated with the aim of evaluating its potential for cytostatic drug and cytotoxicity bioremoval. The toxicity removal was assessed from biomarker test. CP removal of up to 80% was achieved under the operating conditions studied (HRT of 48 h and a SRT of 50 days). The increase of TMP was associated with an increase of supernatant toxicity as if fouling led to retention of the toxicity. Peaks of supernatant cytotoxicity were correlated with peaks in supernatant humic acid contents. It may suggest that molecules with a toxic effect may be adsorbed or entrapped in humic acids substances. Our study then points out that advances in wastewater treatment using an MBR can provide a suitable process for lowering CP concentrations before discharge into the aqueous environment. However, a tertiary treatment is necessary if complete elimination of toxicity is targeted.     

Swine manure fermentation for hydrogen production

Biohydrogen fermentation using liquid swine manure as substrate supplemented with glucose was investigated in this project. Experiments were conducted using a semi-continuously-fed fermenter (8 L in total volume and 4 L in working volume) with varying pHs from 4.7 through 5.9 under controlled temperature (35 ± 1 °C). The hydraulic retention time (HRT) tested include 16, 20, and 24 h; however, in two pH conditions (5.0 and 5.3), an additional HRT of 12 h was also tried. The experimental design combining HRT and pH provided insight on the fermenter performance in terms of hydrogen generation. The results indicated that both HRT and pH had profound influences on fermentative hydrogen productivity. A rising HRT would lead to greater variation in hydrogen concentration in the offgas and the best HRT was found to be 16 h for the fermenter in this study. The best pH value in correspondence to the highest hydrogen generation was revealed to be 5.0 among all the pHs studied. There was no obvious inhibition on hydrogen production by methanogenesis when methane content in the offgas was lower than 2%. Otherwise, an inverse linear relationship between hydrogen and methane content was observed with a correlation coefficient of 0.9699. Therefore, to increase hydrogen content in the offgas, methane production has to be limited to below 2%.     

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.     

Leachate treatment and greenhouse gas emission in subsurface horizontal flow constructed wetland

Organic and nitrogen removal efficiencies in subsurface horizontal flow wetland system (HSF) with cattail (Typha augustifolia) treating young and partially stabilized solid waste leachate were investigated. Hydraulic loading rate (HLR) in the system was varied at 0.01, 0.028 and 0.056 m³/m² d which is equivalent to hydraulic retention time (HRT) of 28, 10 and 5 d. Average BOD removals in the system were 98% and 71% when applied to young and partially stabilized leachate at HLR of 0.01 m³/m² d. In term of total kjeldahl nitrogen, average removal efficiencies were 43% and 46%. High nitrogen in the stabilized leachate adversely affected the treatment performance and vegetation in the system. Nitrogen transforming bacteria were found varied along the treatment pathway. Methane emission rate was found to be highest at the inlet zone during young leachate treatment at 79–712 mg/m² d whereas CO₂ emission ranged from 26–3266 mg/m² d. The emission of N₂O was not detected.     

Enhancement of bioenergy production from organic wastes by two-stage anaerobic hydrogen and methane production process

The present study investigated a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes. A two-stage process with hydraulic retention time (HRT) 3 d for hydrogen reactor and 12 d for methane reactor, obtained 11% higher energy compared to a single-stage methanogenic process (HRT 15 d) under organic loading rate (OLR) 3 gVS/(L d). The two-stage process was still stable when the OLR was increased to 4.5 gVS/(L d), while the single-stage process failed. The study further revealed that by changing the HRT_hydrogen:HRT_methane ratio of the two-stage process from 3:12 to 1:14, 6.7%, more energy could be obtained. Microbial community analysis indicated that the dominant bacterial species were different in the hydrogen reactors (Thermoanaerobacterium thermosaccharolyticum-like species) and methane reactors (Clostridiumthermocellum-like species). The changes of substrates and HRT did not change the dominant species. The archaeal community structures in methane reactors were similar both in single- and two- stage reactors, with acetoclastic methanogens Methanosarcina acetivorans-like organisms as the dominant species.     

Hydrodynamic behaviors in fermentative hydrogen bioreactors by pressure fluctuation analysis

Three bioreactor configurations were employed in these investigations, which consisted of working volumes of 10, 1.2 and 1.2 L. Power spectrum diagrams of bed pressure fluctuation were used with hydraulic retention times (HRT) and geometric factors to identify the flow regimes in the bioreactors, where HRT varied from 8 to 1 h. It was found that the flow regimes in the bioreactors changed from a dispersed regime to coalesced and slugging regimes, when the biogas production rate (BPR) increased, as a result of decreasing the operating HRT. The flow regime was a dispersed bubble regime when the HRT was higher than 4 h in the bioreactor, whereas when the HRT was 2 h the coalesced bubble phenomena occurred in the bioreactor. A slugging regime was found when the HRT was lower than 1 h in thinner bioreactor.     

Toxicological effects of inorganic nanoparticles on human lung cancer A549 cells

Many researches have shown that anionic clays can be used as delivery carriers for drug or gene molecules due to their efficient cellular uptake in vitro, and enhanced permeability and retention effect in vivo. It is, therefore, highly required to establish a guideline on their potential toxicity for practical applications. The toxicity of anionic clay, layered metal hydroxide nanoparticle, was evaluated in two human lung epithelial cells, carcinoma A549 cells and normal L-132 cells, and compared with that in other human cancer cell lines such as cervical adenocarcinoma cells (HeLa) and osteosarcoma cells (HOS). The present nanoparticles showed little cytotoxic effects on the proliferation and viability of four cell lines tested at the concentrations used (<250 μg/ml) within 48 h. However, exposing cancer cells to high concentrations (250-500 μg/ml) for 72 h resulted in an inflammatory response with oxidative stress and membrane damage, which varied with the cell type (A549 > HOS > HeLa). On the other hand, the toxicity mechanism seems to be different from that of other inorganic nanoparticles frequently studied for biological and medicinal applications such as iron oxide, silica, and single walled carbon nanotubes. Iron oxide caused cell death associated with membrane damage, while single walled carbon nanotube induced oxidative stress followed by apoptosis. Silica triggered an inflammation response without causing considerable cell death for both cancer cells and normal cells, whereas layered metal hydroxide nanoparticle did not show any cytotoxic effects on normal L-132 cells in terms of inflammation response, oxidative stress, and membrane damage at the concentration of less than 250 μg/ml. It is , therefore, highly expected that the present nanoparticle can be used as a efficient vehicle for drug delivery and cancer cell targeting as well.     

Using enriched cultures for elevation of anaerobic syntrophic interactions between acetogens and methanogens in a high-load continuous digester

Volatile fatty acids (VFAs) are key intermediates in anaerobic digestion. Enriched acetogenic and methanogenic cultures were used for syntrophic anaerobic digestion of VFAs in a high-load continuous reactor fed with acetic (HAc), propionic (HPr) and butyric (HBu) acids at maximum concentrations of 5, 3 and 4 g/L, respectively. Interactive effects of HPr, HBu and HAc were analyzed. Furthermore, hydraulic retention time (HRT) and methanogen to acetogen population ratio (M/A) were investigated as key microbiological and operating variables of VFA anaerobic degradations. Optimum conditions were found to be HPr = 1125.0 mg/L, HBu = 1833.4 mg/L, HAc = 1727.4 mg/L, HRT = 21 h and M/A = 2.5 (corresponding to maximum VFA removal and biogas production rate (BPR)). Results of verification experiments and predicted values from fitted correlations were in close agreement at 95% confidence interval. HRT and M/A had positive effects on VFA removal and BPR. M/A was the most important factor that affected BPR. All VFAs inhibited VFA removals.     

Histopathological changes induced by maneb and carbaryl on some tissues of rainbow trout, Oncorhynchus mykiss

Acute toxicity of the pesticides, maneb and carbaryl, to juvenile rainbow trout were evaluated under static-renewal test conditions. Actual concentrations of maneb ranged from 0.10 mg/L to 2.00 mg/L and carbaryl ranged from 0.20 mg/L to 3.90 mg/L. The concentrations of maneb that killed 50% of the rainbow trout (3.27 ± 0.9 g) within 24-h (24-h; LC₅₀), 48-h, 72-h and 96-h were 1.19 ± 0.12, 1.04 ± 0.11, 0.92 ± 0.12 and 0.81 ± 0.14 mg/L (95% confidence limits), respectively. LC₅₀ values of carbaryl for 24-h, 48-h, 72-h and 96-h were 2.52 ± 0.71, 2.16 ± 0.63, 1.71 ± 0.46 and 1.39 ± 0.15 mg/L, respectively. None of the unexposed control fish died and the first fish died 6 h after exposure to maneb (≥1.30 mg/L), and carbaryl (≥2.60 mg/L). Lamellar edema, separation of epithelium from lamellae, lamellar fusion, swelling of the epithelial cells and epithelial cell necrosis were observed on maneb and carbaryl exposed fish. Gills also had scattered areas of focal lamellar hyperplasia. Fish exposed to pesticides had inflammation and focal necrosis in liver, trunk kidney and spleen. Maneb and carbaryl had similar histopathological lesions. In order, the most affected organs were gill, trunk kidney and liver.     

Cryopreservation of red snapper (Lutjanus argentimaculatus) sperm: Effect of cryoprotectants and cooling rates on sperm motility, sperm viability, and fertilization capacity

Sperm cryopreservation of red snapper (Lutjanus argentimaculatus) is essentially unexplored, although many species of the Lutjanidae family are considered to be high-value commercial species. The objective of this study was to develop a species-specific cryopreservation protocol for red snapper (L. argentimaculatus) sperm by optimizing cryoprotectants and cooling rates in the cryopreservation procedure. Ten cryoprotectants at four concentrations and two freezing protocols were examined in two separate experiments. In the first experiment, toxicity studies of dimethyl sulfoxide (DMSO), glycerol, propylene glycol (PG), ethylene glycol (EG), formamide, methanol, ethanol, sucrose, trehalose, and dimethylacetamide (DMA) on sperm motility were performed. Semen diluted 1:1 in Ringer solution were exposed to cryoprotectants at four final concentrations of 5%, 10%, 15%, or 20% for periods of 10, 20, 30, 40, 50, 60, 90, and 120 min at room temperature (25 °C). The cryoprotectants and concentrations that showed the least toxic effect on sperm motility were selected for cryopreservation trials. In the second experiment, selected cryoprotectants were then assessed for freezing capacity of sperm as follows: DMSO 5% and 10%, PG 5% and 10%, EG 5% and 10%, ethanol 5%, and methanol 5%. Semen was diluted 1:1 in Ringer solution and equilibrated with selected cryoprotectants for 10 min at room temperature. Sperm were frozen in a controlled-rate programmable freezer at four cooling rates of 3, 5, 10, and 12 °C/min from an initial temperature of 25 °C to final temperatures of −40 or −80 °C before plunging into liquid nitrogen. Sperm equilibrated in 10% DMSO and cooled at a rate of 10 °C/min to a final temperature of −80 °C had the highest motility (91.1 ± 2.2%) and viability (92.7 ± 2.3%) after thawing. The fertilization rate of frozen-thawed sperm (72.4 ± 2.4%) was not different (P > 0.05) from that of fresh sperm (75.5 ± 2.4%). This study apparently represents the first reported attempt for cryopreservation of L. argentimaculatus sperm.     

Hydrogen and methane production through two-stage mesophilic anaerobic digestion of olive pulp

The present study focused on the anaerobic biohydrogen production from olive pulp (two phase olive mill wastes, TPOMW) and the subsequent anaerobic treatment of the effluent for methane production under mesophilic conditions in a two-stage process. Biohydrogen production from water-diluted (1:4) olive pulp was investigated at hydraulic retention times (HRT) of 30 h, 14.5 h and 7.5 h while methane production from the effluent of hydrogenogenic reactor was studied at 20 d, 15 d, 10 d and 5 d HRT. In comparison with previous studies, it has been shown that the thermophilic hydrogen production process was more efficient than the mesophilic one in both hydrogen production rate and yield. The methanogenic reactor was successfully operated at 20, 15 and 10 days HRT while it failed when an HRT of 5 days was applied. Methane productivity reached the maximum value of 1.13 ± 0.08 L/L/d at 10 days HRT whereas the methane yield increased with the HRT. The Anaerobic Digestion Model no. 1 (ADM1) was applied to the obtained experimental data from the methanogenic reactor to simulate the digester response at all HRT tested. The ability of the model to predict the experimental results was evident even in the case of the process failure, thus implying that the ADM1 could be a valuable tool for process design even in the case of a complex feedstock. In general, the two-stage anaerobic digestion proved to be a stable, reliable and effective process for energy recovery and stabilization treatment of olive pulp.