The science of the total environment

Cultivating microalgae in wastewater for biomass production, pollutant removal, and atmospheric carbon mitigation; a review.

Biowaste-to-bioplastic (polyhydroxyalkanoates): Conversion technologies, strategies, challenges, and perspective

Hydrothermal carbonization (HTC) of wet solid wastes has been pointed out as an eco-friendly, flexible and highly efficient technology for the sustainable valorization of multiple sourced wastes. In this review paper, most recent studies on hydrochars (solid residue of the HTC process) production, characterization and application for wastewaters treatment was summarized and deeply discussed. The role of initial feedstock source nature and characteristics as well as the HTC experimental conditions including the temperature, the residence time and the pH media was assessed. Physical and chemical activation methods including the use of oxygen, steam, microwave, acids, alkaline, organics and salty solutions for the improvement of the physicochemical properties of the produced hydrochars are compared. The efficiency of these raw/modified hydrochars along with the involved mechanisms during organic (dyes) and mineral pollutants (heavy metals and nutrients) removal from aqueous solutions is also reviewed. Finally, this paper addresses the main challenges and also demonstrates insights on new directions for hydrochars research and development in the future.

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Hydrochars production, characterization and application for wastewater treatment: A review

The quest for a chemical surfactant substitute has been fuelled by increased environmental awareness. The benefits that biosurfactants present like biodegradability, and biocompatibility over their chemical and synthetic counterparts has contributed immensely to their popularity and use in various industries such as petrochemicals, mining, metallurgy, agrochemicals, fertilizers, beverages, cosmetics, etc. With the growing demand for biosurfactants, researchers are looking for low-cost waste materials to use them as substrates, which will lower the manufacturing costs while providing waste management services as an add-on benefit. The use of low-cost substrates will significantly reduce the cost of producing biosurfactants. This paper discusses the use of various feedstocks in the production of biosurfactants, which not only reduces the cost of waste treatment but also provides an opportunity to profit from the sale of the biosurfactant. Furthermore, it includes state-of-the-art information about employing municipal solid waste as a sustainable feedstock for biosurfactant production, which has not been simultaneously covered in many published literatures on biosurfactant production from different feedstocks. It also addresses the myriad of other issues associated with the processing of biosurfactants, as well as the methods used to address these issues and perspectives, which will move society towards cleaner production.

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A critical review on various feedstocks as sustainable substrates for biosurfactants production: a way towards cleaner production.

Background Demand of dairy products is increasing in different countries, which results in the development of the dairy industry and increases in the generation of wastes. The main wastes generated are whey, dairy sludges and wastewater (processing, cleaning and sanitary). They have high nutrient concentration, biological oxygen demand (BOD), chemical oxygen demand (COD) and organic and inorganic contents. Furthermore, they can contain different sterilizing agents and a wide range of acid and alkaline detergents. Pollution due to dairy industry affects the air, soil and water quality. Scope and approach This review aims to describe the different methods used by the dairy industry to treat wastes, highlighting their effects on quality and efficiency removal of the pollution. Especially, it focusses on biotechnological alternatives to utilize the dairy wastes. Key findings and conclusions Physico-chemical, biological, and biotechnological methods can be used for treatment of dairy wastewaters. The physico-chemical treatment is used for reduction of milk fat and protein colloids, but it has the disadvantages of the high cost of the reagents and limited removal of COD. Biological treatments are used to remove organic material from dairy waste, however, the formation of sludge during aerobic biodegradation is a disadvantage. Aerobic and anaerobic process treatments can be used together in order to reach the effluents discharge limits for dairy wastewater. Biotechnological processes are the most recent alternatives, and can result in important products to the industries, such as whey-derived products, bioplastics, biofuels, bioenergy, organic acids, bioactive peptides, enzymes, among others.

Treatment and utilization of dairy industrial waste: A review

This study aimed to carry out a diagnosis of the cheese whey exploitation by the Brazilian dairy industry using a questionnaire survey. The dairy industries (n=100) were mainly from Southeast (55%) and South (25%) regions and supervised by the Federal Inspection System (80%). Most of them produced (67%) and processed (60%) sweet cheese whey, using it in whey dairy beverages (60%), Ricotta (20%), whey concentrate (15%), and milk blends (5%), which were resold for supermarkets (53%) or industries (20%). However, 27% of the industries discard whey in the effluent treatment system or use as animal feed, suggesting a market for using this by-product.

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Bruna C. V. Soares

Papers

Treatment and utilization of dairy industrial waste: A review

Cheese whey exploitation in Brazil: a questionnaire survey