Clean-soil Air Water最新文献

The global population is increasing at an elevated speed leading to the expansion of urbanization at the cost of environmental degradation, especially aquatic ecosystem pollution due to the enhanced discharge of wastewater. These aquatic ecosystems are primarily polluted by potentially toxic elements, polyaromatic hydrocarbons, dyes, plastics, pesticides, organic compounds, and molecules present in fertilizers, household wastes, industrial effluents, and sewage discharge. The enhanced deterioration of water bodies has led to the search for natural solutions for a sustainable ecosystem. The utilization of the natural microbial flora of the aquatic ecosystem for remediation, more popularly known as bioremediation, is of global interest because of its cost-effectiveness and eco-friendly approach. Bioremediation can be broadly categorized into bacterial remediation, mycoremediation, and phytoremediation and is more commonly studied for soil pollution. However, in this review, we discuss bioremediation techniques and mechanisms with respect to water pollution. Aquatic microbes utilize the toxic components present in wastewater as a substrate for their own metabolism by acting as a biologically active methylator or by chemical alteration of the toxicants into less harmful products, thus degrading the toxic environmental pollutants into nontoxic products thereby eliminating their detrimental effects. Microalgae used in phytoremediation also help to elevate the dissolved oxygen level in the aquatic ecosystem thereby reducing the probability of eutrophication. This review represents the study of diverse pollutants remediation and a method involving microbial consortia in a bioreactor for optimum efficacy at minimum cost.

Polycyclic aromatic hydrocarbons (PAHs) are a diverse group of hazardous and toxic pollutants widely distributed in the environment. The anaerobic degradation is a promising technique for the removal of recalcitrant aromatic hydrocarbons from waste stream. In this study, anaerobic degradation of naphthalene (NAP) was investigated by using cow dung-enriched mixed microbial consortia with varying NAP and sulfate concentrations. The maximum removal of NAP (99.8%) and sulfate (68%) was achieved while varying the sulfate concentration from 50 to 500 mg/L in 500 mg/L NAP influent concentration. 41.9 mg/L of sulfate was generated during this study. Similarly, when NAP concentration was varied from 100 to 1000 mg/L, 84% of chemical oxygen demand (COD), 74% of sulfate, and 92% of NAP were observed at constant sulfate concentration of 250 mg/L. This result reveals that sulfate concentration had no significant effect on NAP degradation. NAP mineralization was evidenced by the formation of sulfide and production of metabolites with decreasing NAP concentration. Gas chromatography–mass spectrometry (GC–MS) confirmed the formation of metabolites like naphthol and 1,2-dihydroxynaphthalene due to monooxygenation at C-1 as part of the metabolic pathway. The rate of NAP, COD, and sulfate removal followed the first-order kinetics with high regression coefficients while varying the influent NAP concentrations.

Discharging effluents with high chemical oxygen demand (COD) and nitrogen content into the environment threatens human and aquatic life. An increase in nitrogen load results in depletion of dissolved oxygen (DO), eutrophication, ecological stress, and biodiversity loss. Intake of water containing excess nitrate can cause different diseases. Conventional physicochemical nitrogen removal techniques are expensive and also generate secondary pollutants. In contrast, biological methods offer effective and economical outcomes with global acceptance. Biofilm-based techniques have the advantages of low space requirement, resistance toward toxic shocks, and absence of sludge backflow. The carriers used in biofilm reactors allow the growth of heterogeneous microbial consortia, which can simultaneously remove COD, nitrogenous compounds, and phosphates. This review aims to summarize the outcomes of the individual lab-scale research in this area, critically analyze the scientific findings, and understand the research gap. Conventional nitrification–denitrification and anammox have often been replaced by more efficient approaches such as simultaneous nitrification–denitrification, partial nitrification–denitrification, partial nitritation and anammox, and simultaneous partial nitrification, anammox, and denitrification. Multistage moving bed biofilm reactors have been specially designed with step feeding for complete nitrogen removal. Through anammox in a sequencing batch reactor, a high rate of denitrification could be obtained, whereas simultaneous nitrification–denitrification using a membrane bioreactor resulted in almost complete removal of nitrogen. We expect that this review will provide the direction for designing experiments on enhanced removal of nitrogen and COD from different wastewater sources using microbial biofilms.

In a changing climate, conservation tillage and agronomic biofortification are essential for enhancing crop yield, nutritional security, carbon stocks, and soil quality. Consequently, a field study was conducted in central India to assess the short-term (4 years) effects of crop establishment techniques (CETs) and agronomic biofortification methods (ABMs) on soil health indicators, grain yield, and quality in the soybean–wheat cropping system. The experiment followed a split-plot design with two CETs in the main plots (permanent broad bed furrow, PBBF, and conventional tillage, CT) and eight ABMs, each with three replications. The results indicated that PBBF and ABMs (seed inoculation with the microbial strains MDSR 14 + MDSR 34, and soil and foliar application of Zn+Fe) improved soil carbon stock (by 49.6% and 52.4%), available nitrogen, phosphorus, potassium, available Zn (by 30.0%), and Fe (by 21.9%) after the fourth year of the study. Similarly, PBBF and microbial inoculation increased soil enzyme activities (dehydrogenase, acid phosphatase, and β-glucosidase), substrate-induced respiration, and microbial biomass carbon content. As a result, a higher soybean equivalent yield (5.59% higher in PBBF and 14.2% higher with foliar spray of Zn+Fe) and seed quality attributes (crude protein yield, grain Zn, and Fe) were observed in PBBF and the foliar spray of Zn and Fe treatments compared to CT and control, respectively. Overall, adopting the short-term PBBF system, microbial inoculation, and soil and foliar application of Zn and Fe improved rhizosphere biochemical properties, yield, and seed quality in the soybean–wheat system.

Synthetic microfibers are emerging environmental microplastic pollutants released from different industrial and domestic sources. The present investigation describes the isolation of potential bacterial strains from microplastic-contaminated sites of Bhubaneswar city of Odisha, India. Four morphologically distinct bacterial strains were isolated using 2% polyethylene glycol (PEG) supplemented nutrient agar (NA) medium and were screened for their polymer tolerance ability by growing them on 2%–8% PEG. A single microorganism capable of growing on 8% PEG was selected for biodegradation experiment. Through 16S rRNA sequencing, the selected bacterial strain was identified as Exiguobacterium sp. with gene bank accession number ON318396. The microbial strain's microfiber biodegradation ability was assessed in a laboratory setting over a period of 28 ± 2 days, utilizing optimized conditions with an initial pH of 7, 2 mL inoculum volume, an incubation temperature of 30°C ± 2°C, and 150 rpm, using 2 g of polyester microfiber. In optimum conditions, the weight loss of the treated sample with the selected microbial strain was 19.2%. The polyester degradation was confirmed through scanning electron microscopic images viewing the degradation of the polyester microfiber surfaces. Variation in functional groups confirmed through Fourier transform infrared spectrophotometry. Detection of carbonyl (C═O) group stretching band at 1711 cm⁻¹ through ATR-FTIR analysis in the treated sample confirmed the polymer biodegradation. The potential isolate can efficiently degrade polyester and, in the future, can be employed as a promising solution for the sustainable treatment of synthetic microfiber pollution.