Microbial community structure and dynamics in a membrane bioreactor supplemented with the flame retardant dibromoneopentyl glycol

Review on rewiring of microalgal strategies for the heavy metal remediation - A metal specific logistics and tactics

Phycoremediation of heavy metals are gaining much attention and becoming an emerging practice for the metal removal in diverse environmental matrices. Still, the physicochemical state of metal polluted sites is often found to be complex and haphazard in nature due to the irregular discharge of wastes, that leads to the lack of conjecture on the application of microalgae for the metal bioremediation. Besides, the foresaid issues might be eventually ended up with futile effect to the polluted site. Therefore, this review is mainly focusing on interpretative assessment on pre-existing microalgal strategies and their merits and demerits for selected metal removal by microalgae through various process such as natural attenuation, nutritional amendment, chemical pretreatment, metal specific modification, immobilization and amalgamation, customization of genetic elements and integrative remediation approaches. Thus, this review provides the ideal knowledge for choosing an efficient metal remediation tactics based on the state of polluted environment. Also, this in-depth description would provide the speculative knowledge of counteractive action required for pass-over the barriers and obstacles during implementation. In addition, the most common metal removal mechanism of microalgae by adsorption was comparatively investigated with different metals through the principal component analysis by grouping various factor such as pH, temperature, initial metal concentration, adsorption capacity, removal efficiency, contact time in different microalgae. Conclusively, the suitable strategies for different heavy metals removal and addressing the complications along with their solution is comprehensively deliberated for metal removal mechanism in microalgae.

Organic wastes bioremediation and its changing prospects

Increasing inappropriate anthropogenic activities and industrialization have resulted in severe environmental pollution worldwide. Their effective treatment is vital for general health concerns. Depending on the characteristics of pollutants, the severity of pollution may differ. For sustainable treatment of polluted environments, bioremediation is accepted as the most efficient, economical, and environmentally friendly method hence largely preferred. However, every bioremediation technique has its own unique advantages and limitations due to its defined applications criteria. In bioremediation, microorganisms play a decisive role in detoxification by degrading, mineralizing and accumulating various forms of harmful and biodegradable pollutants from the surroundings and transforming them into less lethal forms. Bioremediation is performed ex-situ or in-situ, based on location of polluted site as well as characteristics, type and strength of the pollutants. Furthermore, the most popular methodologies for bioremediation include bioaugmentation, biostimulation, bioattenuation among others which depend on the prevailing environmental factors into the microbial system. Implementing them appropriately and effectively under ex-situ or in-situ method is extremely important not only for obtaining efficient treatment but also for the best economic, environmental, and social impacts. Therefore, this review aims to analyze various bioremediation methods for organic pollutants remediation from soil/sediments and wastewater, their strength, limitation, and insights for the selection of appropriate bioremediation techniques based on nature, types, degree, and location of the pollution. The novelty aspect of the article is to give updates on several key supporting technologies which have recently emerged and exhibited great potential to enhance the present bioremediation efficiency such as nanobubble, engineered biochar, mixotrophic microalgae, nanotechnology etc. Moreover, amalgamation of these technologies with existing bioremediation facilities are significantly changing the scenario and scope of environmental remediation towards sustainable bioremediation.

Inhibitory regulation of purple sweet potato polysaccharide on the hepatotoxicity of tri-(2,3-dibromopropyl) isocyanate

Tri-(2,3-dibromopropyl) isocyanate (TBC), a new emerged persistent organic pollutant, is widely used in fields of flame retardant, textile, rubber and plastic with strong hepatotoxicity. Purple Sweet Potato Polysaccharide (PSPP) has antioxidant and hepatoprotective effects. This study aims to answer the scientific question whether PSPP has a protective effect on TBC induced liver injury. The effect of PSPP on the apoptosis of HepG2 cells was detected by MTT assay, the morphological changes were observed by morphological observation, and the apoptosis rate was determined by flow cytometry. The apoptotic genes were detected by qPCR assay, the relevant protein express was detected by western blot. The correlation between proteins and genes in the apoptosis pathway of HepG2 cells was calculated. To further reveal the apoptosis mechanism of TBC hepatotoxicity in vivo, 19 target genes and 14 apoptotic related proteins of inhibiting apoptosis via death receptor and mitochondria were discussed, all the above results proved that PSPP had protective effect on liver injury induced by TBC. This study not only provided a scientific basis for clarifying the mechanism of TBC hepatotoxicity and the protective effect of PSPP, but also generated the new point and method in terms of the prevention in advance and early intervention of diseases caused by environmental pollution.

Bibliometric Analysis of Hydrocarbon Bioremediation in Cold Regions and a Review on Enhanced Soil Bioremediation

Simple Summary

Anthropogenic activities in cold regions require petroleum oils to support various purposes. With the increased demand of petroleum, accidental oil spills are generated during transportation or refuelling processes. Soil is one of the major victims in petroleum pollution, hence studies have been devoted to find solutions to remove these petroleum hydrocarbons. However, the remote and low-temperature conditions in cold regions hindered the implementation of physical and chemical removal treatments. On the other hand, biological treatments in general have been proposed as an innovative approach to attenuate these hydrocarbon pollutants in soils. To understand the relevancy of biological treatments for cold regions specifically, bibliometric analysis has been applied to systematically analyse studies focused on hydrocarbon removal treatment in a biological way. To expedite the understanding of this analysis, we have summarised these biological treatments and suggested other biological applications in the context of cold conditions.

Abstract

The increased usage of petroleum oils in cold regions has led to widespread oil pollutants in soils. The harsh environmental conditions in cold environments allow the persistence of these oil pollutants in soils for more than 20 years, raising adverse threats to the ecosystem. Microbial bioremediation was proposed and employed as a cost-effective tool to remediate petroleum hydrocarbons present in soils without significantly posing harmful side effects. However, the conventional hydrocarbon bioremediation requires a longer time to achieve the clean-up standard due to various environmental factors in cold regions. Recent biotechnological improvements using biostimulation and/or bioaugmentation strategies are reported and implemented to enhance the hydrocarbon removal efficiency under cold conditions. Thus, this review focuses on the enhanced bioremediation for hydrocarbon-polluted soils in cold regions, highlighting in situ and ex situ approaches and few potential enhancements via the exploitation of molecular and microbial technology in response to the cold condition. The bibliometric analysis of the hydrocarbon bioremediation research in cold regions is also presented.

Positive effects of zeolite powder on aerobic granulation: Nitrogen and phosphorus removal and insights into the interaction mechanisms

Aerobic granular sludge is considered one of the most promising biological wastewater treatment technologies of the 21st century. However, the long granulation time and poor treatment effect on N and P have severely limited its popularity and large-scale application. In this study, we systematically examine the strengthening effects of zeolite powder on granulation, N and P removal, and their interaction mechanisms. The addition of zeolite powder decreased sludge granulation time to 18 d, and improved average N and P removal rates by 4.48% and 2.22%, respectively. The multi-pore and nutrient-rich environment of the zeolite powder is beneficial for maintaining microbial activity and granular stability. Moreover, its adsorption to N and P enriches their respective removal strains, improving their removal efficiency.

Bioremediation techniques-classification based on site of application: principles, advantages, limitations and prospects

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

Toward a novel membrane process for organic carbon removal-fate of slowly biodegradable substrate in super fast membrane bioreactor

The study tested the performance of super fast membrane bioreactor (SFMBR) using starch as a slowly biodegradable substrate, exploring the fate of starch, and the response of the microbial community. SFMBR was operated at extremely low sludge ages of 0.5-2.0 days, with a hydraulic retention time of 1.0 h. Average values for permeate chemical oxygen demand (COD) always remained in the narrow range between 14 and 18 mg/L, regardless of the selected mode of MBR operation at different sludge ages. Soluble COD levels in the reactor were consistently higher than the corresponding permeate COD. Parameters defining process kinetics, determined by model calibration of oxygen uptake rate (OUR) profiles, varied as a function of sludge age. Model simulation of SFMBR performance indicated total removal of hydrolysis products so that permeate COD consisted of residual microbial products. PCR-DGGE experiments revealed significant shifts in the composition of the microbial community imposed by variations in the sludge age, reflecting on corresponding process kinetics.