Endophytic bacteria enhance remediation of tannery effluent in constructed wetlands vegetated with Leptochloa fusca

The use of constructed wetlands (CWs) is a promising approach for the remediation of wastewater. The present study aims to develop a plant–bacteria system within CWs for the efficient remediation of tannery effluent. In a vertical-flow CW vegetated with Leptochloa fusca (Kallar grass), a consortium of three different endophytic bacteria, Pantoea stewartii ASI11, Microbacterium arborescens HU33, and Enterobacter sp. HU38, was used for bioaugmentation. CWs vegetated with only L. fusca had the potential to remediate tannery effluent, but augmentation with endophytic bacteria enhanced the growth of L. fusca while aiding in the removal of both organic and inorganic pollutants from the tannery effluent. Moreover, the bacterial augmentation decreased toxicity in the effluent as well. A higher number of chromium (Cr)-resistant bacteria were isolated from the rhizosphere and endosphere of L. fusca inoculated with the endophytes than from uninoculated plants. Due to promising bioremediation and detoxification potential of L. fusca, it is reported for the first time as a potential candidate to develop effective CWs for the remediation of polluted effluents in combination with pollutant-degrading endophytic bacteria.     

Industrial wastewater treatment in internal circulation bioreactor followed by wetlands containing emergent plants and algae

Wastewater treatment based on ecological principles is a low cost and highly desirable solution for the developing countries like Pakistan. The present study evaluated the effectiveness of biological treatment systems including Internal Circulation (IC) anaerobic bioreactor and constructed wetlands (CWs) containing macrophytes and mixed algal cultures for industrial wastewater treatment. The IC bioreactor reduced COD (52%), turbidity (89%), EC (24%) of the industrial wastewater. However, the effluents of IC bioreactor did not comply with National Environmental Quality Standards (NEQS) of Pakistan. Post-treatment of IC bioreactor effluents was accomplished in CW containing macrophytes (Arundo donax and Eichhornia crassipes) and mixed algal culture. The CWs planted with macrophytes lowered the concentrations of COD (89%) and turbidity (99%). CWs with algal biomass were not effective in further polishing the effluent. Inhibition of algal biomass growth was observed due to physicochemical characteristics of wastewater. The integrated treatment system consisting of IC bioreactor and macrophytes was found more suitable option for industrial wastewater treatment.     

Bacterial diversity, organic pollutants and their metabolites in two aeration lagoons of common effluent treatment plant (CETP) during the degradation and detoxification of tannery wastewater

In this study, PCR-RFLP and GC-MS approaches were used to characterize the bacterial diversity, organic pollutants and metabolites during the tannery wastewater treatment process at common effluent treatment plant (CETP). Results revealed that the bacterial communities growing in aeration lagoon-I were dominated with Escherichia sp., Stenotrophomonas sp., Bacillus sp. and Cronobacter sp. while that of aeration lagoon-II prevailed with Stenotrophomonas sp., and Burkholderiales bacterium, respectively. The HPLC and GC-MS analysis revealed that most of the organic pollutants detected in untreated tannery wastewater samples were diminished from bacterial treated tannery wastewater samples. Only two pollutants i.e. L-(+)-lactic acid and acetic acid could not be degraded by bacteria whereas benzene and 2-hydroxy-3-methyl-butanoic acid was produced as new metabolites during the bacterial treatment of tannery wastewater in aeration lagoon II of CETP. Further, it was observed that after bacterial treatment, the toxicity of tannery effluent was reduced significantly allowing 90% seed germination.     

Constructed Wetlands for Tannery Wastewater Treatment in Portugal: Ten Years of Experience

Wastewaters from tannery industry are complex in composition and providing adequate treatment can be difficult. Constructed wetlands (CW) are regarded as an alternative treatment to the conventional biological systems, as a developing cost-effective and environmentally friendly phytoremediation technology. The present review compiles and integrates information on CWs technology for the needs of the tannery sector. The following issues arise as crucial for the implementation of such systems, namely i) an accurate wastewater characterization and an effective pretreatment before reaching the CW, ii) choosing the plants species better adapted to the imposed conditions, iii) substrate selection and iv) range of organic loadings applied. The examples practiced in Portugal give indication that horizontal subsurface flow systems, with expanded clay media, are a suitable option to be considered when dealing with high organic loading tannery wastewater (up to c.a. 3800 kgCODha^?1d^?1), being resilient to a wide range of hydraulic variations. Plants such as Phragmites and Typha have shown to be adequate for tannery wastewater depuration, with Arundo donax proving resilient to high salinity wastewaters. The flexibility of implementation allows the CW to be adapted to different sites with different configurations, being suitable as main secondary or tertiary treatment stage.     

Phycoremediation resultant lipid production and antioxidant changes in green microalgae Chlorella Sp.

In this investigation, we report on the treatment of tannery wastewater using microalgae Chlorella species to produce lipid and fatty acid as well as changes in antioxidant metabolism during the treatment. The variation in growth, production of pigments, antioxidant metabolism, lipid and fatty acids, and nutrient removal from wastewater during the remediation were observed. Surprisingly, a profuse growth was found in 50% diluted tannery wastewater (TW), which supported to accumulate high yield of lipid (18.5%) and unsaturated fatty acids (50.05%). The antioxidant activity of microalgae in both the concentrations (50% and 100% TW) were viz., lipid peroxidation 1.6 ± 0.1 and 2.3 ± 0.02nmol MDA mg^?1 protein, SOD 10.3 ± 0.4 and 15.7 ± 0.9 U mg^?1 protein, CAT 0.17 ± 0.036 and 0.52 ± 0.06 U mg^?1 protein, and APX 7.2 ± 0.8 and 11.2 ± 09 U mg^?1 protein respectively, which point out that the free radical scavenging mechanism against heavy metal stress. Maximum phycoremediation of heavy metals observed from both concentrations during the healthy growth period were Cr – 73.1, 45.7%, Cu – 90.4, 78.1%, Pb – 92.1, 52.2%, and Zn – 81.2, 44.6%, respectively. This study proved the potential use of Chlorella for heavy metal and nutrient removal from tannery wastewater. Moreover, an unaffected growth with high antioxidant activity of this species promises a sustainable lipid and fatty acid contents for biofuel production.     

The use constructed wetlands with horizontal sub-surface flow for various types of wastewater

Constructed wetlands with horizontal sub-surface flow (HF CWs) have been used for wastewater treatment for more than 30 years. Most HF CWs have been designed to treat municipal or domestic wastewater. Nowadays, municipal HF CWs focus not only on common pollutants but also on special parameters such as pharmaceuticals, endocrine disruptive chemicals or linear alkylbenzensulfonates (LAS). At present, HF CWs are used to treat many other types of wastewater. Industrial applications include wastewaters from oil refineries, chemical factories, pulp and paper production, tannery and textile industries, abattoir, distillery and winery industries. In particular, the use of HF CWs is becoming very common for treatment of food-processing wastewaters (e.g., production and processing of milk, cheese, potatoes, sugar). HF constructed wetlands are also successfully used to treat wastewaters from agriculture (e.g., pig and dairy farms, fish farm effluents) and various runoff waters (agriculture, airports, highway, greenhouses, plant nurseries). HF CWs have also effectively been used to treat landfill leachate. Besides the use as a single unit, HF CWs are also used in combination with other types of constructed wetlands in hybrid systems.     

谷子秸秆不同部位水浸液对3种杂草的化感作用

通过测定种子萌芽期生物学指标和盆栽苗期生理指标,研究谷子不同部位(叶片、茎秆)不同浓度(原液、10倍稀释液、50倍稀释液、100倍稀释液)浸提液对反枝苋、藜、狗尾草3种谷田恶性杂草的化感作用。结果表明: 谷子叶片、茎秆水浸提液对3种杂草均存在显著化感作用,且不同浓度浸提液化感作用存在差异,总体表现为原液有抑制作用,稀释液(10、50、100倍)有促进作用。叶片、茎秆浸提液原液处理下,反枝苋、藜、狗尾草的发芽率分别下降了63.9%、37.3%和41.7%,根长仅为对照的27.8%、37.8%和18.4%,芽长仅为对照的34.5%、27.7%和17.6%,净光合速率为对照的66.6%、89.9%和88.2%,蒸腾速率为对照的69.0%、87.5%和56.1%,原液对3种杂草的综合化感效应指数为-0.699、-0.716和-0.795,表现出较强的化感抑制作用。稀释液处理下化感促进作用随稀释倍数增加呈先上升后下降趋势,其中50倍稀释液促进作用最强,3种杂草的发芽率、根长和芽长均与对照达到差异显著水平,综合化感效应指数分别为0.261、0.217和0.165。谷田伴生杂草大量生长与谷子秸秆中化感物质淋溶有关。     

Effect of Toxic Compounds of Exserohilum turcicum on Chlorophyll Content, Callus Growth and Cell Viability of Susceptible and Resistant Inbred Lines of Maize

Toxicity of toxic compounds in the culture filtrates of Exserohilum turcicum towards seed germination, inhibition of shoot and root growth, callus growth and on reduction in chlorophyll content and cell viability of maize was studied. There was no germination in unautoclaved extracts at 100% (undiluted) and 50% concentrations, whereas germination was normal at all the concentrations of autoclaved toxic compounds. Inhibition of root growth was higher compared with that of shoot growth in all the test preparations of toxic compounds. Reduction in total chlorophyll and also chlorophyll a and b contents of disease resistant (KWTC-17) and susceptible (DK-4) inbreds occurred at 50, 25 and 10% concentrations of toxic compounds, with maximum reduction in the susceptible compared with the resistant inbred. Chlorophyll a was found to be more sensitive, showing 7.2% reduction in content in susceptible inbred even at 5% toxin concentration. Callus cultures/cell suspensions derived from coleotible nodes of DK-4 were more sensitive compared with that of KWTC-17 in all the test concentrations of toxic compounds. Callus growth of susceptible inbred DK-4 was inhibited by 32.7% compared with 15.31% of resistant inbred KWTC-17 at 5% concentration of toxic compounds. Cell viability of resistant and susceptible inbreds was 62.0% and 20.2% at 10% toxic concentration, respectively. Spore germination assay with four fungal species or leaf puncture assay were not found useful.     

Phytoremediation of chromium by model constructed wetland

Chromium is a pollutant present in tannery wastewater, its removal is necessary for protection of the environment. Penisetum purpureum, Brachiaria decumbens and Phragmites australis were grown hydroponically in experimental gravel beds to determine their potential for the phytoremediation of solutions containing 10 and 20 mg Cr dm(-3). These concentrations, similar to tannery wastewater after initial physico-chemical treatment were used with the aim of developing an economic secondary treatment to protect the environment. All the systems achieved removal efficiencies of 97-99.6% within 24 h. P. purpureum and B. decumbens removed 78.1% and 68.5% respectively within the first hour. Both P. purpureum and B. decumbens were tolerant of the concentrations of chromium applied, but P. purpureum showed the greatest potential because its faster growth and larger biomass achieved a much greater chromium removal over the whole length of time of the experiment.     

Effectiveness of Rice Agricultural Waste,Microbes and Wetland Plants in the Removal of Reactive Black-5 Azo Dye in Microcosm Constructed Wetlands

Azo dyes are commonly generated as effluent pollutants by dye using industries, causing contamination of surface and ground water. Various strategies are employed to treat such wastewater; however, a multi-faceted treatment strategy could be more effective for complete removal of azo dyes from industrial effluent than any single treatment. In the present study, rice husk material was used as a substratum in two constructed wetlands (CWs) and augmented with microorganisms in the presence of wetland plants to effectively treat dye-polluted water. To evaluate the efficiency of each process the study was divided into three levels, i.e., adsorption of dye onto the substratum, phytoremediation within the CW and then bioremediation along with the previous two processes in the augmented CW. The adsorption process was helpful in removing 50% dye in presence of rice husk while 80% in presence of rice husk biocahr. Augmentation of microorganisms in CW systems has improved dye removal efficiency to 90%. Similarly presence of microorganisms enhanced removal of total nitrogen (68% 0 and Total phosphorus (75%). A significant improvement in plant growth was also observed by measuring plant height, number of leaves and leave area. These findings suggest the use of agricultural waste as part of a CW substratum can provide enhanced removal of textile dyes.     

Effect of textile effluents on growth performance of wheat cultivars

Laboratory experiments were conducted to study the effect of different concentrations in the range of 0-100% textile effluents (untreated and treated) on seed germination (%), delay index (DI), plant shoot length and root length, plant biomass, chlorophyll content and carotenoid of three different cultivars of wheat. The textile effluent did not show any inhibitory effect on seed germination at low concentration (6.25%). The other reported plant parameters also followed the similar trend. Seeds germinated in undiluted effluents did not survive for longer period. Based on the tolerance to textile effluent, the wheat cultivars have been arranged in the following order: PBW-343 < PBW-373 < WH-147. It has also been concluded that effect of the textile effluent is cultivar specific and due care should be taken before using the textile effluent for irrigation purpose.     

Substrate effect on bacterial communities from constructed wetlands planted with Typha latifolia treating industrial wastewater

Constructed wetlands (CWs) have been recognized as being able to effectively treat wastewater from municipal and industrial sources. This study focused on the effect of different substrates and long-term operation of horizontal subsurface flow CWs treating tannery wastewater on the bacterial communities. The CWs were planted with Typha latifolia in three types of substrate: two units with different types of expanded clay aggregates and one unit with fine gravel. Another unit with expanded clay was left unvegetated. Changes in the bacterial community related to the type of substrate, different hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). Bacterial enumeration was also performed and several bacterial isolates were retrieved from the CWs. Phylogenetic affiliations of those isolates were obtained on the basis of 16S rRNA gene sequences and revealed that they were closely related to the genera Bacillus (TM1S1, TM1R3, TNR1 and TAR1), Paracoccus (TM1R2), Pseudomonas (TM1R1) and Halomonas (TM1S2).The type of substrate and the presence of T. latifolia had a major effect on the species richness and the structure of bacterial communities as inferred by numerical analysis of DGGE profiles.     

Impact of loads,season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds

The effects of wastewater loading rates and two macrophyte species on treatment of sugar factory stabilization pond effluent were investigated in a pilot-scale free water surface constructed wetland (FWS CW) system in western Kenya. For 12 months, four CWs were operated at a hydraulic loading rate of 75 mm day⁻¹ and four at 225 mm day⁻¹. Half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Water samples were taken at the inlets and outlets and analyzed for TP, TDP, NH₄-N, and TSS. Mass removal rates of the selected water quality parameters were compared during three periods designated the short rain (period 1), dry (period 2), and long rain (period 3) seasons. There was a significant linear relationship between the mass removal rate of TP, NH₄-N, and TSS and the mass load, and season had a significant effect on the mass removal rate of TSS, NH₄-N, and TDP. Mass loading rates for TDP were about 78% of those for TP, whereas TDP comprised 78–99% of TP mass outflow rates, indicating a release of dissolved P within the CWs. The only significant difference between the two macrophyte species was associated with mass removal of NH₄-N, with more efficient removal in CWs planted with C. papyrus than those with E. pyramidalis. TP mass removal rates were 50–80% higher when a mean water loss for CWs 6–8 during periods 1 and 2 was assumed to represent evapotranspiration for all CWs in period 3 instead of pan evaporation data. This illustrated the importance of accurate estimations of evapotranspiration for pollutant mass removal rates in CWs in tropical climates.     

Evaluation of methods to solubilize and analyze cell-associated ectoenzymes

A protocol for production, storage, and use of Shock 1 (Shk1) bioreporter cells for toxicity monitoring in wastewater treatment facilities was developed. Shk1 is a bioluminescent toxicity bioreporter for activated sludge previously constructed by the incorporation of lux genes into an activated sludge microorganism.

A number of factors affecting Shk1 growth and bioluminescence were examined including the growth medium, tetracycline concentration, storage conditions, and test media. Based on the results of these experiments, a toxicity testing protocol was developed that involved growth of cultures in nutrient broth with tetracycline, storage of cultures at 4 °C, cell activation by reinoculation into nutrient broth, and toxicity testing by cell injection into the test media. Effective use of this approach required standardized time intervals for cell growth, storage, activation and exposure in the test media.

Bioluminescence from Shk1 cells was measured in nutrient broth and influent wastewater and activated sludge mixed liquor from a municipal wastewater treatment plant. Using the Shk1 toxicity testing protocol, Zn EC₅₀ values for bioluminescence in nutrient broth, influent wastewater, and activated sludge mixed liquor were approximately 42, 7, and 32 mg/l, respectively. Zn concentrations as low as 1 mg/l could be detected in influent wastewater. The detection limit in influent wastewater is below the Zn concentrations typically reported to affect the activated sludge process.     

Effect of toxic substances in anaerobic treatment of tannery wastewaters

Studies were carried out in the treatment of tannery wastewater using upflow anaerobic contact filter (reactor) and on the role of toxic substances viz tannin, sulphide, chromium (3+) in inhibiting the performance of the reactor. The influent COD concentration was varied in the range of 1500 to 16500?mg/l, at different hydraulic retention times viz 36,48,60 hr. The limiting concentrations of toxicity for the three substances viz tannin, sulphide, chromium (3+) were identified in terms of the performance of the reactor viz COD removal percent, biogas production etc. Toxic limits of the above mentioned substances were further estimated in batch process (in vials) to supplement the evidence. In anaerobic contact filter tannin beyond 914?mg/l inhibited the performance, whereas sulphide concentration even upto 180?mg/l and chromium (3+) concentration even upto 140?mg/l did not affect the reactor performance. In batch process tannin above 77 wt.% affected the anaerobic microbial growth. Hydrolysable tannin was present in these tannery wastewaters.     

Characterization of sorption sites and differential stress response of microalgae isolates against tannery effluents from ranipet industrial area—An application towards phycoremediation

Phycoremediation ability of microalgae namely Oscillatoria acuminate and Phormidium irrigum were validated against the heavy metals from tannery effluent of Ranipet industrial area. The microalgae species were cultured in media containing tannery effluent in two different volumes and the parameters like specific growth rate, protein content and antioxidant enzyme activities were estimated. FTIR spectroscopy was carried out to know the sorption sites interaction. The antioxidant enzymes namely superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) contents were increased in microalgae species indicating the free radical scavenging mechanism under heavy metal stress. SOD activity was 0.502 and 0.378 units/gram fresh weight, CAT activity was 1.36 and 0.256 units/gram fresh weight, GSH activity was 1.286 and 1.232 units/gram fresh weight respectively in the effluent treated microalgae species. Bio sorption efficiency for Oscillatoria acuminate and Phormidium irrigum was 90% and 80% respectively. FTIR analysis revealed the interaction of microalgae species with chemical groups present in the tannery effluent. From the results, the microalgae Oscillatoria acuminate possess high antioxidant activity and bio sorption efficiency when compared to Phormidium irrigum and hence considered useful in treating heavy metals contaminated effluents.     

Effect of distillery effluent on seed germination in some vegetable crops

A laboratory experiment was conducted to study the effect of different concentrations (0%, 5%, 10%, 15%, 20%, 25%, 50%, 75% and 100%) of distillery effluent (raw spent wash) on seed germination (%), speed of germination, peak value and germination value in some vegetable crops: tomato, chilli, bottle gourd, cucumber and onion. The distillery effluent did not show any inhibitory effect on seed germination at low concentration except in tomato, but in onion the germination was significantly higher (84%) at 10% concentration as against 63% in the control. Irrespective of the crop species, at highest concentrations (75% and 100%), complete failure of germination was observed. The speed of germination, peak value and germination value also followed a similar trend. We found that a concentration of 5% was critical for seed germination in tomato and bottle gourd, and 25% in the rest of the crops. Based on the tolerance to distillery effluent, the crops studied have been arranged in the following order: cucumber > chilli > onion > bottle gourd > tomato. We conclude that the effect of the distillery effluent is crop-specific and due care should be taken before using the distillery effluent for pre-sowing irrigation purposes.     

Bioremediation of sago industry effluent and its impact on seed germination (green gram and maize)

In this study, we attempted two investigational systems: one is treatment of sago industry effluent by aerobic bacterial consortium and the other is impact of treated and untreated effluent on seed germination. For the treatment system, the starch degrading bacteria were isolated from sago industry effluent and effluent contaminated soil. The genera, Alcaligenes, Bacillus and Corynebacterium were found efficient in starch degradation. The selected isolates were tested for their efficiency on the degradation of starch both in Mineral Salts Medium (MSM) and in sago industry effluent. About 85% of the starch was degraded in MSM by a bacterial consortium composed of Alcaligenes, Bacillus and Corynebacterium, whereas in effluent the degradation of starch was only 63%. The physico-chemical properties such as electrical conductivity, total solids, suspended solids, dissolved solids, BOD, COD, nitrogen and phosphate were found decreased in effluent after 72 h. The pH of the effluent was relatively increased from 3 to 6.7. The study of seed germination (maize and green gram) was carried out at 25, 50, 75 and 100% concentrations of treated and untreated effluent using soil sowing method. Shoot length, root length, fresh weight, dry weight and chlorophyll content showed an increase when treated effluent was tested whereas a decrease of growth was noticed in untreated effluent tested seedlings. The results revealed that effluent treated by aerobic microorganisms has no negative impact on the seed germination and can be effectively used for irrigation.     

工业废水的鱼类急性毒性效应研究

利用斑马鱼对某市六家有代表性的企业所排放的处理前和处理后的工业废水进行了急性毒性试验,以对斑马鱼的半致死浓度为评价指标,得到了六种工业废水毒性强度的初步排序,并结合理化指标分析了斑马鱼的致死原因。实验表明,六家企业处理前工业废水的毒性大小顺序为:电子类>食品类>电镀类>电池类>玻璃类>橡胶类,96hLC₅₀分别为:0.98%、4.73%、11.35%、13.60%、47.60%,其中橡胶类毒性最小,100%的工业废水对斑马鱼无致死效应。处理后的工业废水毒性基本消除,但部分行业的工业废水处理后仍存在毒性。     

Fate of metallic engineered nanomaterials in constructed wetlands: prospection and future research perspectives

Metallic engineered nanomaterials (ENMs) undergo various transformations in the environment which affect their fate, toxicity and bioavailability. Although constructed wetlands (CWs) are applied as treatment systems for waste streams potentially containing metallic ENMs, little is known about the fate and effects of ENMs in CWs. Hence, literature data from related fields such as activated sludge wastewater treatment and natural wetlands is used to predict the fate and effects of ENMs in CWs and to analyze the risk of nanomaterials being released from CWs into surface waters. The ENMs are likely to reach the CW (partly) transformed and the transformations will continue in the CW. The main transformation processes depend on the type of ENM and the ambient environmental conditions in the CW. In general, ENMs are expected to undergo sorption onto (suspended) organic matter and plant roots. Although the risk of ENMs being released at high concentrations from CWs is estimated low, caution is warranted because of the estimated rise in the production of these materials. As discharge of (transformed) ENMs from CWs during normal operation is predicted to be low, future research should rather focus on the effects of system malfunctions (e.g. short-circuiting). Efficient retention in the CW and increasing production volumes in the future entail increasing concentrations within the CW substrate and further research needs to address possible adverse effects caused.