IntroductionMicrobial fuel cell (MFC) is a potential environmental friendly bioelectrochemical system as it combines treatment of organic wastes and electric energy generation [1][2][3][4]. In MFCs, the electrochemically active microorganisms' biofilm colonizes the anodic surface thus oxidizing organic pollutants producing electrons and protons. Electrons are transferred through an external circuit to the cathode where are received by the terminal electron acceptor while protons migrate through the membrane or solution to the cathode to keep electrical neutrality which creates potential difference [1,5]. Several applications of this technology such as hydrogen gas production [6], hydrogen peroxide generation [7], desalination [8][9][10], remote sensors and monitoring devices [11,12] metal recovery at cathode [13] and robots [12,14] to mention but few, have been studied and left researchers with more innovation ideas in the field. Having electrochemical processes catalyzed by biological processes in addition to some other design parameters such as engineering of microbial biofilm structure, decrypting electron transfer mechanisms, cell/reactor configuration, electrode materials and geometries, substrate concentration, retention time, and optimizing cathode catalysts [15,16] makes this system more sensitive to internal losses and gives it a certain level of complexity [17,18]. This and other challenges that are still unanswered are the bottlenecks for MFC application in real environment [15,19]. Therefore, current researches focus on limiting factors and ways to curb their effects thus increasing the performance [2,20,21]. Among others, is trying different MFC design configurations where MFC aircathode proved to more advantageous over double chamber for scaling up because of its simple structure, low cost and direct use oxygen in air, which could removes aeration from conventional wastewater treatment process [5,22]. Due to its high reduction potential and inexhaustible source, Oxygen is the most fairly used terminal electron acceptor and is considered to be competent for MFC air-cathode application and scale up as it plays a critical role in both organic oxidation and energy recovery at the cathode [23]. AbstractMicrobial fuel cell (MFC) air cathode present a great potential among other configurations due to its simple design, low cost and direct use oxygen from air as terminal electron acceptor which could help to save tremendous energy used for aeration in conventional wastewater treatment. However, at the cathode oxygen reduction reaction which is vital to generate high power density is naturally slow, therefore a catalyst is needed to overcome its reaction over-potential. Platinum (Pt) is the standard used catalyst in large number of oxidation reduction reactions whether in basic or acidic electrolytes. But, due to its high cost and limited resources it doesn't make it a sustainable candidate for scaling up of this juvenile technology. Activated carbon was found to be a low cost and environmental friendly Ox...

In te rnation a l J o u rn al of W a s te R es ourc e s AbstractWastewater treatment for urban areas has become a very important factor in the improvement of environmental quality. Increasing rates of urbanisation has increased environmental stresses, emphasising the importance of environmental protection. Sewage treatment is the most effective method to improve water quality. However, a recent increase in the sewage treatment rates has not improved the overall water quality in China. Data collected from the China Statistical Yearbooks has shown that there has been an increase in sewage treatment rates, particularly in larger cities. With 3350 wastewater treatment facilities ranging from super large facilities that can cater to a population of 1 million, to small facilities that cater to smaller populations of less than 100 000. The overall water quality remained low due to the unavailability of wastewater pipelines to connect to the WWTP. Possible ways to improve the situation is to introduce water reuse systems, which requires a certain percentage of water is expected to return to the water supply. This will replenish stressed water sources as well as provide incentive to ensure wastewater is effectively transported for treatment.

Abstract Biochar, coal produced by pyrolysis and used as an amendment, has several advantages and has proven to be a promising avenue for sustainable agriculture. However, the current manufacturing methods, the conditions of pyrolysis and the biomasses used produce biochars of very variable qualities which can differently affect the productivity of the ground and the outputs of plants. Currently, no study makes it possible to elucidate the influence of the physicochemical properties of the biochars on the structure and the microbial diversity of the soil. The aim of this review was to understand how the physicochemical properties of a biochar affect its capacity: to reduce the emissions of greenhouse gases; to improve the growth of hothouse plants; to improve the effectiveness of the use of manures and water; and to modify the structure and the diversity of the bacterial communities in a horticultural substrate and a mineral soil. These biochars were produced under various conditions. The analyses show that the addition of biochar can stimulate certain groups of bacteria involved in carbon and nitrogen cycles and possibly those involved in the development of plants. This review identifies the important physicochemical properties of the biochars, which will be able to better guide agricultural producers and industries manufacturing substrates containing peat, in the choice of a biochar favorable to the growth of plants and a more durable agriculture.

Abstract The use of a large number of organic pollutants results in the accumulation of effluents at the places of production and the environment. These substances are, therefore, dangerous for living organisms and can cause heavy environmental damage. Hence, to cure these problems certain methods were used for the elimination of organic effluents. Indeed, the methods of elimination through magnetic adsorption and/or separation prove to be effective in the treatment of certain wastes, but the effectiveness of each one of these methods depends on several characteristics and also present limitations according to the pollutants they adsorb. This review examines on the one hand the capacity of certain elements of these methods in the elimination of certain pollutants and on the other hand the advantages and limits of these methods. Elements like biochars, biosorbents and composite materials are used due to their very strong porosity which makes it possible for them to develop an important contact surface with the external medium, at low costs, and the possibility of producing them from renewable sources. The latter still run up however against the problems of formation of mud and regeneration. Depollution by magnetic separation is also used due to its capacity to mitigate the disadvantages of certain methods which generally lead to the formation of mud and overcoming also the difficulties like obtaining an active material and at the same time being able to fix the pollutants present in the effluents to treat and sensitize them to external magnetic fields.