Microalgae-based agro-industrial wastewater treatment: a preliminary screening of biodegradability

The potential of algal–bacterial symbiosis for the removal of carbon, nitrogen and phosphorus from five agro-industrial wastewaters was investigated in enclosed batch biodegradation tests using a mixed microalgae consortium and activated sludge as model microorganisms. The target wastewaters were obtained from potato processing (PW), fish processing (FW), animal feed production (MW), coffee manufacturing (CW) and yeast production (YW). The initial C/N/P ratio of the agro-industrial wastewater was correlated with its biodegradability. Thus, the highest removals of total organic carbon (TOC) and nitrogen were recorded in two fold diluted FW (64?±?2 % and 85?±?1 %, respectively), while the maximum P-PO₄ ^3? removal achieved was 89?±?1 % in undiluted PW. The biodegradable TOC was in most cases the limiting component in the treatment of the wastewaters evaluated. This study confirmed the potential of coupling carbon and nutrient recovery from agro-industrial effluents with the production of a valuable algal–bacterial biomass, despite their poor biodegradability.     

Capacities and limits of three different technologies for the biological treatment of leachate from solid waste landfill sites

Leachate from a municipal waste landfill site was treated using an activated sludge bioreactor, a fluidized bed biofilm reactor and a packed-bed column reactor (trickling filter). The leachate contained high organic matter (2.0–2.6 g/l of COD), high ammonium (300–700 mg/l) and sulphide (200–800 mg/l) concentrations, as well as low metal concentrations. The continuously operating reactors were employed to study the effects of TOC loading on the removal of TOC as well as on the nitrification and denitrification processes. Among the three biological treatment technologies investigated, the fluidized bed biofilm reactor was best with respect to removing ammonia and TOC. More than 90% of TOC and 99% of ammonia were removed when TOC loading was less than 0.5 kg/m³ × d. At a TOC loading of 4 kg/m³ × d, the removal of TOC and ammonia was 80% and 99%, respectively. In contrast, the treatment of leachate with the packed-bed reactor was successful in TOC removing only at TOC loading less than 0.3 kg/m³ × d (TOC elimination decreased from 86% at 0.06 kg/m³ × d to 60% at 0.3 kg/m³ × d). However, the reactor was active in nitrification even at a higher TOC loading (more than a 98% ammonia elimination at a TOC loading of 0.5 kg/m³ × d). Leachate was processed in the activated sludge reactor when TOC loading was less than 0.5 kg/m³ × d (with a removal of TOC and ammonia up to 83% and 99%, respectively). The activated sludge reactor was also effective in TOC removal at a higher TOC loading (e.g. a 74% TOC removal at a TOC loading of 1 kg/m³ × d), but for ammonia elimination, the activity continuously decreased (less than 60% ammonia removal at a TOC loading of 1 kg/m³ × d). Overloading in the activated sludge system was indicated by a high concentration of ammonia and nitrite in the effluent. In the packed bed reactor, overloading was characterized by a progressively incomplete TOC removal. No significant overloading was found in the fluidized bed reactor up to a TOC loading of 4 kg/m³ × d.     

Study of Microflora in Malaysian Dried Fishes and Their Decontamination by Gamma-irradiation

The distribution of microorganisms in 10 samples of salted dried fish and the effects of irradiation of them were studied. The total aerobic bacteria in commercial dried fish were determined to be from 2 × 10⁴ to 3 × 10⁶ per gram. Mold counts were 1 × 10² to 7 × 10³ per gram with a lower amount of yeasts. In spoiled dried fish, total aerobic bacteria were determined to be 4× 10⁶ or 1 × 10⁷ per gram with a few yeasts. Coliforms were not isolated on MacConkey agar plates from any of the samples. The predominant bacteria occurring in spoiled dried fish were Pediococcus halophilus, Vibrio costicola and Planococcus sp. More than 50% of the molds consisted of the Aspergillus niger group, whereas lower amounts of the A. flavus, A. fumigatus and A. ochraceus groups, Penicillium chrysogenum series, etc. were also isolated from many samples of dried fish. All kinds of putrefactive microorganisms were radiation sensitive, and a dose of ca. 500 krad appears to be sufficient for extension of the shelf-life of dried fish from 2 to 4 times.     

Bioremediation of synthetic high–chemical oxygen demand wastewater using microalgal species Chlorella pyrenoidosa

The microalgal species Chlorella pyrenoidosa was cultivated in synthetic wastewater of initial chemical oxygen demand (COD), nitrate, and phosphate concentrations of 5000, 100, and 40 mg/L, respectively. The aim of the study was to find out the tolerance of microalgae to different COD concentrations and the extent of COD degradation at those concentrations. Three dilutions of wastewater (initial COD concentrations 5000, 3000, and 1000 mg/L) and three inoculum sizes (0.1, 0.2, and 0.3 g/L) were considered for the study. The experimental parameters such as total organic carbon, total inorganic carbon, COD, optical density, total solids, nitrate, and phosphate were measured on a daily basis. Biodegradation kinetics was determined for all cases using first-order reaction and Monod degradation equations. Optimal results showed that up to 90% reduction in TOC was obtained for 1000 COD wastewater while only 38% reduction in total organic carbon (TOC) was achieved for 5000 COD wastewater. Over 95% reduction in nitrate and nearly 90% removal of phosphate were obtained with the lowest microalgal inoculum concentration (i.e., 0.1 g/L) for all COD dilutions. This study showed that microalgal species C. pyrenoidosa can successfully degrade the organic carbon source (i.e., acetate) with significant removal efficiencies for nitrate and phosphate.     

模拟氮沉降和降雨量改变对华西雨屏区常绿阔叶林土壤有机碳的影响

从2013年11月至2015年12月,通过原位试验,在华西雨屏区常绿阔叶林内设置了对照(CK)、氮沉降(N)、减雨(R)、增雨(A)、氮沉降+减雨(NR)、氮沉降+增雨(NA)6个处理水平,研究了模拟氮沉降和降雨量改变对常绿阔叶林土壤有机碳的影响。结果表明:华西雨屏区常绿阔叶林土壤各土层有机碳含量表现为夏季较高,春冬季较低,0—10 cm土层有机碳含量高于10—20 cm土层。从各处理土壤有机碳含量的平均值来看,0—10 cm土层土壤有机碳含量高低顺序表现为:RNRCKANNA;10—20 cm土层表现为:RNRACKNAN。模拟氮沉降和增雨处理促进了华西雨屏区常绿阔叶林土壤有机碳的累积,模拟减雨抑制了土壤有机碳的累积。常绿阔叶林0—10cm土层土壤C/N值显著高于10—20 cm,土壤C/N值随土层加深而呈现出增加的趋势,降雨使土壤C/N降低,增雨使土壤C/N增高。同一氮沉降条件下,增雨处理增加了土壤有机碳的含量,减雨处理减少了土壤有机碳的含量;同一降雨条件下,氮沉降增加土壤有机碳的含量。氮沉降和降雨对土壤可溶解性有机碳和微生物生物量碳含量产生显著影响(P0.05),对土壤活性碳含量影响不显著(P0.05);其交互作用对土壤有机碳、可溶解性有机碳、微生物生物量碳和活性碳含量影响不显著(P0.05)。     

汕头南澳养殖区表层沉积物中生源要素的分布及其污染评价

于2010年9月采集南澳海域鱼类养殖区、贝类养殖区、大型藻类栽培区和对照区4个功能区表层沉积物样品,分析沉积物中生物硅(BSi)、总有机碳(TOC)、总氮(TN)和总磷(TP)4种生源要素的含量。结果表明,南澳海域生源要素含量与国内外养殖区相比属于中等水平。鱼类养殖区TOC、TN、TP的含量最高,而BSi的最高含量出现在藻类栽培区(平均含量为0.30%)。鱼类养殖区BSi、TOC、TN和TP的平均含量分别为0.24%、0.89%、0.13%和0.097%。根据沉积物中TOC/TN比值分析,发现鱼类养殖区的TOC主要来源于水生,贝类、藻类和对照区TOC则主要来源于陆源。生源要素污染评价表明,4个功能区的TN均属于Ⅱ类污染,鱼类和贝类养殖区的TP属于Ⅱ类轻度污染。     

Batch biological treatment of nitrogen deficient synthetic wastewater using Azotobacter supplemented activated sludge

Biological treatment of nitrogen deficient wastewaters are usually accomplished by external addition of nitrogen sources to the wastewater which is an extra cost item. As an alternative for effective biological treatment of nitrogen deficient wastewaters, the nitrogen fixing bacterium, Azotobacter vinelandii, was used in activated sludge and also in pure culture. Total organic carbon (TOC) removal performances of Azotobacter-added and free activated sludge cultures were compared at different initial TN/TOC ratios. The rate and extent of TOC removal were comparable for all cultures when initial TN/TOC ratio was larger than 0.12; however, both the rate and extent of TOC removal from nitrogen deficient (TN/TOC<12%) synthetic wastewater were improved by using Azotobacter-added activated sludge as compared to the Azotobacter-free activated sludge culture. More than 90% TOC removal was obtained with pure Azotobacter or Azotobacter-added activated sludge culture from a nitrogen deficient synthetic wastewater.     

Biosorption and recycling of gold using various microorganisms

In order to obtain basic information on the biosorption and recycling of gold from aqueous systems using microbial cells, the biosorption of gold by various microorganisms was investigated. Of 75 strains of microorganisms tested (25 bacteria, 19 actinomycetes, 17 fungi and 14 yeasts), high abilities of gold biosorption from a solution containing hydrogen tetrachloroaurate (III) were found in some gram-negative bacterial strains, such as Acinetobacter calcoaceticus, Erwinia herbicola, Pseudomonas aeruginosa, and P. maltophilia. Most of the gram-positive bacteria, actinomycetes, fungi and yeasts had a lower ability for gold biosorption than gram-negative bacteria. On the other hand, all of the microorganisms tested adsorbed far smaller amounts of gold from a solution containing gold dicyanoaurate (I). The biosorption of gold from a solution containing hydrogen tetrachloroaurate (III) using P. maltophilia having a high adsorbing ability for gold was very rapid and was affected by the pH of the solution, external gold concentration, and cell amounts. P. maltophilia cells immobilized with polyacrylamide gel also have a high ability for gold biosorption. The gold adsorbed on the immobilized cells is easily desorbed with 0.1 M thiourea solution. The immobilized P. maltophilia cells can be used repeatedly in biosorption-desorption cycles.     

Microbial community analysis and performance of a phosphate-removing activated sludge

The microbial community of a phosphate-removing activated sludge was analyzed according to the extracted 16S rDNA sequences. The sludge, which accumulated 5.6% P by weight, was obtained from a sequencing batch reactor treating a fatty-acid rich wastewater containing 108 mg l(-1) total organic carbon (TOC), 14.0 mg l(-1) N and 16.2 mg l(-1) P. The reactor at 25 degrees C and pH 7.6 removed over 96% TOC and 99.9% P from the wastewater. According to the 16S rDNA analysis of the 114 clones developed, the sludge had a diverse population, mainly comprising Proteobacteria (71.0%) and the Cytophaga Flavobacterium Bacteroides group (23.7%), plus a few species of Planctomycetales (2.6%), Verrucomicrobiales (1.8%) and Firmicutes (0.9%). Of the 114 clones, 36 (31.6%) were closely affiliated with Acinetobacter. However, Acinetobacter did not accumulate phosphate judging from the images of sludge samples hybridized with an Acinetobacter-specific probe and stained with a phosphate-specific dye. The identities of the phosphate-removing bacteria remain unclear.     

Cultivation of Microalgae in Dairy Farm Wastewater Without Sterilization

The present study investigated the feasibility of cultivating microalgae in dairy farm wastewater. The growth of microalgae and the removal rate of the nutrient from the wastewater were examined. The wastewater was diluted 20, 10 and 5 times before applied to cultivate microalgae. A 5 dilution yielded 0.86 g/L dry weight in 6 days with a relative growth rate of 0.28 d^?1, the 10× dilution gave 0.74 g/L and a relative growth rate of 0.26 d^?1 while the 20× dilution 0.59 g/L and a relative growth rate 0.23 d^?1. The nutrients in the wastewater could be removed effectively in different diluted dairy wastewater. The greatest dilution (20×) showed the removal rates: ammonia, 99.26%; P, 89.92%; COD, 84.18%. A 10× dilution removal% was: ammonia 93; P 91 and COD 88. The 5× dilution removal% was: ammonia 83; P 92; COD 90.     

Effect of pH change on the performance and microbial community of enhanced biological phosphate removal process

An acetate-rich wastewater, containing 170 mg/L of total organic carbon (TOC), 13 mg/L of N, and 15 mg/L of P, was treated using the enhanced biological phosphate removal (EBPR) process operated in a sequencing batch reactor. A slight change of pH of the mixed liquor from 7.0 to 6.5 led to a complete loss of phosphate-removing capability and a drastic change of microbial populations. The process steadily removed 94% of TOC and 99.9% of P from the wastewater at pH 7.0, but only 93% TOC and 17% of P 14 days after the pH was lowered to pH 6.5. The sludge contained 8.8% P at pH 7.0, but only 1.9% at pH 6.5. Based on 16S rDNA analysis, 64.8% of the clones obtained from the sludge at pH 7.0 were absent in the pH 6.5 sludge. The missing microbes, some of which were likely responsible for the phosphate removal at pH 7.0, included beta-Proteobacteria, Actinobacteria, Bacteriodetes/Chlorobi group, plus photosynthetic bacteria and Defluvicoccus of the alpha-Proteobacteria. Among them, the last two groups, which represented 9.3% and 10.1% of the EBPR sludge at pH 7.0, have rarely been reported in an EBPR system.     

Anaerobic treatment of wastewater with high salt content from a pickled-plum manufacturing process

Anaerobic treatment of wastewater with a high salt content generated during a pickled-plum manufacturing process (TOC, 14g/l; ash, 150g/l; pH 2.7, hereafter called pickled-plum effluent) was investigated for its effect on the high salt content of the wastewater. The synthetic wastewater, including NaCl up to 30g/l, was treated anaerobically by a draw and fill method (treatment temperature, 37°C; volumetric loading rate of organic matter, 2g/l·d). The TOC removal efficiency and rate of gas evolution then gradually decreased as salt content increased, although stable operation was maintained. At NaCl concentrations above 30g/l, TOC removal efficiency decreased rapidly and stable operation could not be maintained. Five-fold-diluted pickled-plum effluent was treated by the same method at a volumetric TOC loading rate of 2.9g/l·d with a TOC removal efficiency of 71%. Five-fold-diluted pickled-plum effluent was also treated in an anaerobic fluidized-bed reactor (AFBR) at a maximum volumetric TOC loading rate of 3.0g/l·d, which gave almost the same results as the draw and fill method. However, ten-fold-diluted pickled-plum effluent could be treated in the AFBR at a maximum volumetric TOC loading rate of 11.1g/l·d with a TOC removal efficiency of 84.6%. The red pigment in the pickled-plum effluent was completely decolorized by the anaerobic treatment.     

Treatment of distillery wastewater discharged from beet molasses-spirits production using yeast

Treatment of wastewater discharged from beet molasses-spirits production using yeast was studied. Two flocculant strains, Hansenula fabianii J 640-4-1 and Hansenula anomala J 45-N-5, and a strain, I-44, isolated from soil were suitable for treatment of wastewater at the concentration of 47,300 ppm of total organic carbon (TOC). Especially in the case of 2-step treatment using J 45-N-5 and I-44, TOC decreased to 11,900 ppm, and the C/N ratio (TOC/Total nitrogen) decreased from 14.8 to 4.6.     

Unraveling the decolourizing ability of yeast isolates from dye-polluted and virgin environments: an ecological and taxonomical overview

Microcosm assays with dye-amended culture media under a shot-feeding strategy allowed us to obtain 100 yeast isolates from the wastewater outfall channel of a dyeing textile factory in Tucumán (Argentina). Meanwhile, 63 yeast isolates were obtained from Phoebe porphyria (Laurel del monte) samples collected from Las Yungas rainforest (Tucumán), via a classical isolation scheme. Isolated yeasts, both from dye-polluted and virgin environments, were compared for their textile dye decolourization ability when cultured on solid and liquid media. Nine isolates from wastewater and 17 from Las Yungas showed the highest decolourization potential on agar plates containing six different reactive dyes, either alone or as a mixture. Five yeasts from each environment were further selected on the basis of their high dye removal rate in Vilmafix^® Red 7B-HE- or Vilmafix^® Blue RR-BB-amended liquid cultures. Yeasts from wastewater showed slightly higher decolourization percentages after 36 h of culture than yeasts from Las Yungas (98?C100% vs. 91?C95%, respectively). However, isolates from Las Yungas exhibited higher specific decolourization rates than isolates from effluents (1.8?C3.0 vs. 0.9?C1.3 mg g^?1h^?1, respectively). All selected isolates were first grouped according to microsatellite-PCR analysis and representative isolates from each group were subsequently identified based on the 26S rRNA gene sequence analysis. Yeasts from wastewater were identified as the ascomycetous Pichia kudriavzevii (100%) and closely related to Candida sorbophila (99.8%), whilst yeasts from Las Yungas were identified as the basidiomycetous Trichosporon akiyoshidainum and Trichosporon multisporum. It is suggested that findings concerning yeast selection during screening programs for dye-decolourizing yeasts may be explained in the light of the copiotroph-oligotroph microorganisms rationale.     

Membrane bioreactor wastewater treatment plants reveal diverse yeast and protist communities of potential significance in biofouling

The yeast community was studied in a municipal full-scale membrane bioreactor wastewater treatment plant (MBR-WWTP). The unexpectedly high diversity of yeasts indicated that the activated sludge formed a suitable environment for them to proliferate, with cellular concentrations of 2.2 ± 0.8?×?10³ CFU ml^?1. Sixteen species of seven genera were present in the biological reactor, with Ascomycetes being the most prevalent group (93%). Most isolates were able to grow in a synthetic wastewater medium, adhere to polyethylene surfaces, and develop biofilms of variable complexity. The relationship between yeast populations and the protists in the MBR-WWTP was also studied, revealing that some protist species preyed on and ingested yeasts. These results suggest that yeast populations may play a role in the food web of a WWTP and, to some extent, contribute to membrane biofouling in MBR systems.     

A comparative study of four systems for tertiary wastewater treatment by Scenedesmus bicellularis: New technology for immobilization

Immobilization appears to be one of the best techniques to separate physically micro-algal cells from their culture medium for the purpose of algal tertiary wastewater treatment. High operation costs and other drawbacks of large-scale physico-chemical methods of harvest led to a comparative study of biotreatment systems. Before treatment began, Scenedesmus bicellularis cells were conditioned (starved) under four different sets of conditions: 1) non-immobilized cells with air bubbling (NCA); 2) cells immobilized in alginate beads (CBW) and 3) cells immobilized on alginate screens (CSW), all conditioned in synthetic culture medium depleted in N and P; 4) cells immobilized on alginate screens but conditioned in air at 100% relative humidity (CSA). Starvation was started under a light:dark photoperiod of 16:8 h. Starved cells were then used to treat wastewater for a 2-h period. The performance of each system was evaluated by determination of residual NH₄-N and phosphate ions and by growth (dry weight, total chlorophyll, cell count, protein content). We then tested the capacity of microalgae immobilized on screens to eliminate N and P from a secondary municipal wastewater effluent and examined the influence of temperature and starvation. The quality of treated effluents was improved considerably with the system using CSA or CSW model. For CSA model, the protein content was 22.4 pg cell^-1 compared to 12.9, 9.5, 9.1 pg cell^-1 for NCA, CBW and CSW models, respectively. The CBW and CSW models were efficient for chlorophyll synthesis. The residual ammonium content in natural wastewater after 2 h of treatment with CSA model was 39% at 6±2 °C and reached 100% removal at 18±2 °C. With the first 2 h, the removal of orthophosphate was inferior (53%) at 6±2 °C, but 88 to 100% at 18±2 °C depending on starvation times. Long starvation times (72 or 96 h) caused damage to cells and uptake of nutrients was lower than with 54 h starvation. This work demonstrates that by using immobilization on screens, removal of nutrients from wastewater was higher than with conventional biological tertiary wastewater treatments (free cells or bead-shaped alginate particles).     

Decolorization and degradation of reactive azo dyes by fixed bed bioreactors containing immobilized cells of Proteus vulgaris NCIM-2027

Immobilized cells of Proteus vulgaris NCIM 2027 completely decolorized C.I. Reactive Blue 172 (50 mg/L) within 8 h along with a nearly 80% reduction in TOC and COD. The dye degradation efficiency of the immobilized cells was further improved by optimizing the physicochemical conditions, including agitation, temperature, pH, dye concentration, and biomass loading. Microbial toxicity study revealed the non-toxic nature of the degraded products. Repeated-batch decolorization was conducted to evaluate the reusability of the immobilized cells. The immobilized cells were used for continuous dye decolorization in a fixed bed bioreactor under different volumetric flow rates and dye feeding concentrations. In addition, the immobilized cells were applied to decolorize a mixture of seven reactive dyes in batch and continuous modes, resulting in efficient decolorization (in terms of ADMI value) and significant reduction in TOC and COD. This suggests the potential of using immobilized cells to treat dye-containing wastewater.     

Anaerobic treatment of distillery wastewater from barley-Shochu making by UASB

Distillery wastewater from barley-shochu making was anaerobically treated by a single upflow anaerobic sludge blanket (UASB), and stable operation at a volumetric TOC loading rate of 3 g/l·d could be attained by diluting raw wastewater to give a TOC concentration of less than 6,000 mg/l (18,000 mg/l as CODer). When the distribution of the concentrations of aliphatic acids at various levels within the reactor was investigated, it was found that the methanogenic gasification reaction did not occur in the sludge blanket of the reactor. Distillery wastewater from barley-shochu making with various TOC concentrations was preliminary adjusted to pH 7 and treated by a single passage without circulation of effluent to the bottom of the reactor. As a result, a maximum TOC removal rate (V_max) of 28.5 g/l·d and a saturation constant (K_s) of 0.63 g/l were obtained.     

施肥对雷竹林土壤活性有机碳的影响

采用重施肥料试验研究了不同重施肥习惯对雷竹林土壤碳库产生的影响,结果表明,各有机肥、化肥混合处理土壤总有机碳(TOC)、水溶性碳(WSOC)、微生物量碳(MBC)、矿化态碳(MC)及WSOC/TOC、MBC/TOC和MC/TOC均显著或极显著高于单施化肥各处理.3个有机肥、化肥混施处理中,随着有机肥用量减少,TOC、WSOC、MBC和MBC/TOC显著下降,有机肥用量减少一半,上述各类碳分别下降10.75%、12.02%、30.94%和22.61%.单施化肥处理中,氮素用量超过1009.5 kg·hm^-2·年^-1会使土壤WSOC、MBC、MBC/TOC明显降低.雷竹土壤TOC、WSOC、MBC和MC两两之间相关性均达显著或极显著水平,进一步通过6个处理变异系数分析发现,土壤MBC、MBC/TOC是衡量雷竹土壤碳库质量的最佳指标.     

Algae-based biofilm productivity utilizing dairy wastewater: effects of temperature and organic carbon concentration

Background

Biofilm-based microalgal growth was determined as functions of organic chemical loading and water temperature utilizing dairy wastewater from a full-scale dairy farm. The dairy industry is a significant source of wastewater worldwide that could provide an inexpensive and nutrient rich feedstock for the cultivation of algae biomass for use in downstream processing of animal feed and aquaculture applications. Algal biomass was cultivated using a Rotating Algal Biofilm Reactor (RABR) system. The RABR is a biofilm-based technology that has been designed and used to remediate municipal wastewater and was applied to treat dairy wastewater through nutrient uptake, and simultaneously provide biomass for the production of renewable bioproducts.

Results

Aerial algal biofilm growth rates in dairy wastewater at 7 and 27 °C temperatures were shown to be 4.55?±?0.17 g/m²-day and 7.57?±?1.12 g/m²-day ash free dry weight (AFDW), respectively. Analysis of Variance (ANOVA) calculations indicated that both an increase in temperature of the wastewater and an increase in the level of organic carbon, from 300 to 1200 mg L^-1, contributed significantly to an increase in the rate of biomass growth in the system. However, ANOVA results indicated that the interaction of temperature and organic carbon content was not significantly related to the biofilm-based growth rate.

Conclusion

A microalgae-based biofilm reactor was successfully used to treat turbid dairy wastewater. Temperature and organic carbon concentration had a statistically significant effect on algae-based biofilm productivity and treatment of dairy wastewater. The relationships between temperature, TOC, and productivity developed in this study may be used in the design and assessment of wastewater remediation systems and biomass production systems utilizing algae-based biofilm reactors for treating dairy wastes.