Coffee is globally the second largest most traded commodity after petroleum, and this has facilitated many countries to grow and produce coffee in commercial quantity. The production processes uses large volume of water which comes out as contaminated water. The presence of toxic chemicals like tannins, phenolic and alkaloids inhibits biological degradation. Microbial processes break down the organic substances released into water bodies slowly, using up the oxygen from the water (COD). As demand for oxygen needed to break down organic waste in a wastewater begins to exceed supply, a decrease in oxygen needed to combine with chemicals (COD) slowly creates anaerobic condition. The review looks at few of the current methods (physicochemical and biological) used in coffee wastewater management, their advantages and disadvantages including, high cost implication, complex operation and more time consumption among others; furthermore, the review suggests ion exchange technique as a better alternative based on its capacity to act as both an ion exchanger and absorber.

In recent years, oil and grease has been identified as an emerging pollutant of concern (EPC) in wastewater stream as it can disturb the ecology and wastewater treatment process efficiency. The highest contributor to oily wastewater among domestic wastewater is from kitchen greywater. One of the alternatives to address this problem is the application of enzyme. The production of enzyme by using organic waste has gained significant attention in the recent years due to sustainable demand from it. In this study, pectinolytic enzyme was produced through simplified fermentation from discarded citrus peels that possess high lipase content. Three batches of treatment which consist of the control sample (solely wastewater), 25% (v/v) citrus enzyme + wastewater and 50% (v/v) citrus enzyme + wastewater was incubated in an incubator shaker for 10 days at 30 °C and 150 rpm. The wastewater analysis was performed at a regular interval of 48 h. The parameters monitored were pH, BOD 5 and oil and grease. Laboratory work has demonstrated that 25% (v/v) pectinolytic enzyme was able to remove BOD 5 and oil and grease about 10% better than 50% (v/v) pectinolytic enzyme. The percentage of removal achieved by 25% (v/v) pectinolytic enzyme was 39.83 ± 9.50 mg/L and 64.21 ± 1.12 mg/L, respectively. However, it was observed that enzyme was less effective in removing BOD 5 as the solution contains organic matter that increases the total organic matter in the wastewater mixture.

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This is an era where the application of adsorption and usage of activated carbons (AC) are considered as mainstream water treatments. The upgrade of these materials may only be through its preparation methods, where most researchers have transitioned from using the conventional furnace methods to using microwave ovens. Derived from various precursors, ACs can be the key in developing numerous environmental applications. This paper reviews the development of production processes of AC from various precursors in the past decades by microwave heating. The importance of the applied methodology and how activating conditions play an influential role, such as carbonisation temperature, activation time, and impregnation ratio are also outlined in this review. From the review of AC production processes, ACs produced from various precursors by chemical method with microwave heating have shown to be the significant factor in developing ACs with relatively higher surface area compared to conventional heating ACs.

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