Shahida Shaheen

Anaerobic microbial fuel cell treating combined industrial wastewater: Correlation of electricity generation with pollutants.

Microbial fuel cell (MFC) is a new technology that not only generates energy but treats wastewater as well. A dual chamber MFC was operated under laboratory conditions. Wastewater samples from vegetable oil industries, metal works, glass and marble industries, chemical industries and combined industrial effluents were collected and each was treated for 98h in MFC. The treatment efficiency for COD in MFC was in range of 85-90% at hydraulic retention time (HRT) of 96h and had significant impact on wastewater treatment as well. The maximum voltage of 890mV was generated when vegetable oil industries discharge was treated with columbic efficiency of 5184.7C. The minimum voltage was produced by Glass House wastewater which was 520mV. There was positive significant co-relation between COD concentration and generated voltage. Further research should be focused on the organic contents of wastewater and various ionic species affecting voltage generation in MFC.

Antimony (Sb) – pollution and removal techniques – critical assessment of technologies

In view of increasing emissions of antimony (Sb) into the environment due to industrialization and consequent carcinogenicity, it is essential to remove this metal from the ecosystem. Antimony and arsenic (As) are analogs. Although numerous studies examined arsenic removal, few reports are available on Sb removal. In this review, various Sb removal techniques are described to understand how this process occurs and what research gaps are needed to improve efficiency. At present, surface adsorption technique is the most widely used for Sb removal. Biological treatment namely phytoremediation is also a promising method and more investigations are required in this regard. The selection of a suitable technique for a given area depends on the conditions including economic, environmental, and social conditions.

Phytoremediation Using Algae and Macrophytes: I

Heavy metals are the global environmental contaminants. Their toxicity of various heavy metals to living systems is well established. The most common treatment processes used include chemical precipitation, oxidation/reduction, ion exchange, reverse osmosis, and solvent extraction. Biological methods of metal removal employ various microbes or plant species and are cost-effective as compared to physicochemical methods. Biosorption has become known as a potential and cost-effective alternative for heavy metal exclusion from aqueous solution. Agricultural by-products have also offered a potential alternative as biosorbents for heavy metals among the existing techniques and are yet a subject of broad studies. Agricultural biosorbents including soybean hulls, peanut hulls, almond hulls, cottonseed hulls, and corncobs have also been proven to take out heavy metal ions. The inspiration of using plants for environmental remediation is very ancient and cannot be traced to any meticulous source. In the course of progressively mesmerizing scientific innovations, pooled with interdisciplinary explorations, phytoremediation is considered to be environmentally friendly technology. Various plant species have shown variable potential for metal uptake. As a plant-based technology, the success of phytoextraction is inherently dependent on several plant characteristics, the two most important being the ability to accumulate large quantities of biomass rapidly and the capacity to accumulate large quantities of environmentally important metals in the shoot tissue. The mechanism of metal uptake, translocation, role of rhizosphere in metal uptake, and possibility of using algae in phytoremediation were reviewed.

Transcriptomic responses of selected genes against chromium stress in Arundo donax L.

ABSTRACT Recently, giant reed (Arundo donax L.) has emerged as a useful bioresource capable of coping under harsh abiotic stress conditions produced by exposure to heavy metals, drought and salinity as evidenced by significant biomass production. The current study was undertaken to determine the expression of critical genes involved in resisting oxidative stress and maintaining normal cellular functions. The critical genes examined included glutathione reductase (GR) that prevents oxidative damage of membranes, carotenoid hydroxylase (CR), transcription factor (bHLH) and amidase involved in biosynthesis of indole-3-acetic acid following exposure to chromium (Cr) stress at concentrations of 0, 33.5, 67, 133 or 268 mg/L in giant reed. The S19 gene was used as internal control. It was not possible to extract RNA from severely stressed giant plant leaves at 133 and 268 mg/L Cr. Therefore, this investigation focused on gene expression in the presence of at 0, 33.5 or 67 mg/L Cr. Following Cr-mediated stress, gene expression of GR and CR was increased at 33.5 mg/L but reduced at 67 mg/L. The transcription factor, bHLH, gene expression remained unchanged. Amidase gene expression was elevated at 67 mg/L Cr. Data suggested that over expression of amidase and GR genes at high Cr exposure might increase growth and biomass of giant reed as well as enhance tolerance. These results indicated that giant reed tolerated the presence of Cr stress due to over expression of amidase and GR genes. It would appear that giant reed may serve a beneficial role for phytoremediation of Cr contaminated wastewater and soils at concentrations below 100 mg/kg.

Microbe and plant assisted-remediation of organic xenobiotics and its enhancement by genetically modified organisms and recombinant technology: A review

Environmental problems such as the deterioration of groundwater quality, soil degradation and various threats to human, animal and ecosystem health are closely related to the presence of high concentrations of organic xenobiotics in the environment. Employing appropriate technologies to remediate contaminated soils is crucial due to the site-specificity of most remediation methods. The limitations of conventional remediation technologies include poor environmental compatibility, high cost of implementation and poor public acceptability. This raises the call to employ biological methods for remediation. Bioremediation and microbe-assisted bioremediation (phytoremediation) offer many ecological and cost-associated benefits. The overall efficiency and performance of bio- and phytoremediation approaches can be enhanced by genetically modified microbes and plants. Moreover, phytoremediation can also be stimulated by suitable plant-microbe partnerships, i.e. plant-endophytic or plant-rhizospheric associations. Synergistic interactions between recombinant bacteria and genetically modified plants can further enhance the restoration of environments impacted by organic pollutants. Nevertheless, releasing genetically modified microbes and plants into the environment does pose potential risks. These can be minimized by adopting environmental biotechnological techniques and guidelines provided by environmental protection agencies and other regulatory frameworks. The current contribution provides a comprehensive overview on enhanced bioremediation and phytoremediation approaches using transgenic plants and microbes. It also sheds light on the mitigation of associated environmental risks.

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.

Tolerance Mechanisms of Rice to Arsenic Stress

Arsenic (As) has been found to be allied part of various minerals like iron, oxides/hydroxides of aluminum, manganese, and sulfides in the earth crust. The toxicity caused by As in soil can affect paddy crop because the associated risk of As human health is mainly owed to the bioavailable species of As. Rice (Oryza sativa L.) is a most common staple food in Asia and worldwide which uptakes and accumulates As in it. The understanding of arsenic (As) biogeochemical cycle in paddy soils is very important which is related with the mobility, solubility, and bioaccessibility of this heavy metal. Rhizosphere of paddy soil becomes favorable for the oxidation of to AsIII to AsV due to the release of oxygen from roots of rice plants, development of iron plaque, and oxidation activities of rhizobacteria. Reductive dissolution of arsenopyrite discharges As(V) into groundwater, whereas dissolution of claudetite produces As(III). The article aimed to discuss the As uptake and its metabolism by rice plants when encountered with As contamination.

Physiology and selected genes expression under cadmium stress in Arundo donax L

ABSTRACT The effects of cadmium stress (0, 25, 50, 75, and 100 mg/L) on morpho-physiological features and selected genes (carotenoid hydroxilase, amidase, GR, bHLH, NRAMP and YSL) expression were demonstrated in Arundo donax L. The plants were assessed for Cd uptake and its effects on chlorophyll and antioxidants after 30 days of exposure. The expression of genes conferring metal tolerance was evaluated after 10 days of Cd exposure. The results showed a maximum Cd uptake in roots (872 mg/kg) followed by stem (734 mg/kg) and leaves (298 mg/kg) at highest supplied Cd concentration. The Cd uptake reduced dry weight, Chla, Chlb, and total Chl contents of giant reed. The SOD, CAT, POD activities and MDA content increased at the maximum Cd concentration over control. The highest genes expression for carotenoid hydroxylase, glutathione reductase and amidase was observed in plants exposed to 100 mg/L. However, differential bHLH gene expression and slightly increased gene expression of NRAMP was noted for different Cd treatments. Amidase expressed under Cd stress which is pioneer report in A. donax. These results provided insights into the mechanisms of A. donax tolerance and survival under Cd Stress.

Genetic Control of Metal Sequestration in Hyper-Accumulator Plants

Heavy metal contamination is an emergent environmental dilemma all over the world, posing serious threat to environment as well as human being by disturbing the ecological balance. There are a number of physical, chemical, and biological techniques applicable worldwide for wastewater treatment, but the phytoremediation techniques are the green, sustainable, and promising solutions to problem of environmental contamination. Studies revealed that there are certain hyper-accumulator genes present in plants, which make them more metal tolerant than non-hyper-accumulator plants species where those genes are absent. In addition, hyper-accumulator plants tackle with heavy metals by activating their responsive genes for chelation, trafficking, and sequestration. Therefore, studying such hyper-accumulator genes opens a gateway for the thorough understanding of phytoremediation techniques.