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This review critically evaluates the types and concentrations of key illicit drugs (cocaine, amphetamines, cannabinoids, opioids and their metabolites) found in wastewater, surface water and drinking water sources worldwide and what is known on the effectiveness of wastewater treatment in removing such compounds. It is also important to amass information on the trends in specific drug use as well as the sources of such compounds that enter the environment and we review current international knowledge on this. There are regional differences in the types and quantities of illicit drug consumption and this is reflected in the quantities detected in water. Generally, the levels of illicit drugs in wastewater effluents are lower than in raw influent, indicating that the majority of compounds can be at least partially removed by conventional treatment processes such as activated sludge or trickling filters. However, the literature also indicates that it is too simplistic to assume non-detection equates to drug removal and/or mitigation of associated risks, as there is evidence that some compounds may avoid detection via inadequate sampling and/or analysis protocols, or through conversion to transformation products. Partitioning of drugs from the water to the solids fraction (sludge/biosolids) may also simply shift the potential risk burden to a different environmental compartment and the review found no information on drug stability and persistence in biosolids. Generally speaking, activated sludge-type processes appear to offer better removal efficacy across a range of substances, but the lack of detail in many studies makes it difficult to comment on the most effective process configurations and operations. There is also a paucity of information on the removal effectiveness of alternative treatment processes. Research is also required on natural removal processes in both water and sediments that may over time facilitate further removal of these compounds in receiving environments.

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The removal of gummy or mucilaginous substances from vegetable oils, commonly known as degumming, is required for the use of crude vegetable oils as the feedstock for biodiesel production. These gums reduce the rate of transesterification reactions by deactivation of the catalyst and they hinder the separation of the glycerol phase from the biodiesel. They also cause the deposition of carbon particles within engine machinery and affect performance. To take care of these issues, gums should be separated from the oils to make the oils suitable for use as fuel. Chemical treatment, membrane separation, and biological separation processes have been reported in the literature for this purpose. In the chemical treatment process aqueous solutions of chemicals like acids, bases, ethylenediaminetetraacetic acid (EDTA), and water are used for separating gums. The membrane separation process is based on size exclusion, and polymeric, ceramic, and inorganic membranes are used to separate gums from oil. In biological degumming, phospholipase groups of enzymes are used. These enzymes hydrolyze gums into fatty acids and lipophilic substances. Enzyme degumming also enhances oil‐phase yield. This paper reviews the chemical nature of gums and presents a comprehensive critical summary of different degumming technologies, their specific features, effecting parameters, advantages and disadvantages, and industrial uses. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.