Biological wastewater treatment: comparative method / Nurul Syairah Mohd Fadzil

Water is a natural resource that is essential for all living things. However, owing to the growth of the human population and eco-unfriendly practices, fresh water has been enormously polluted over the past century and form a low-quality water called wastewater. As mentioned, wastewater may come from the domestic, industrial, agricultural or commercial activities, surface runoff and any sewer inflow. The wastewater might cause severe threats to the environment which affects all kind of living organisms. Therefore, wastewater should be treated properly. Wastewater treatment is a system used to extract and transform pollutants from wastewater into effluent that can be added to the water cycle with an appropriate environmental effect or reused for different purposes. There are three classifications treatment process which are physical, chemical and biological treatment. This review study elucidates about the biological wastewater treatment using different small organisms such as algae, fungi, bacteria and yeast. Biological treatment is more preferred than chemical treatment since it is more economical and environmentally friendly. Besides, these microorganisms are effective for the treatment and have lots of advantages. For instance, these microorganisms are nontoxic, not require fresh water to grow, biodegradable, have high growth rate as well as it do not use arable land. The presence of algae, fungi, bacteria and yeast in the wastewater are to break down organic wastes which are mainly for nitrate, phosphate, ammonia and to remove the chemical oxygen demand (COD) and biological oxygen demand (BOD) in the wastewater. The removal percentage of these aspects have been discussed in this review which showed that yeast is able to remove COD up to 95% while algae can remove BOD, nitrate and phosphate up to 85.61%, 100% and 97.8%, respectively. Biological wastewater treatment can be done in continuous flow reactor or batch reactor with several methods like oxidation pond, aerated lagoon, and trickling filter. From this review, we can identify that most common method used for algae is high-rate algal pond (HRAP). Thus, this review summarizes and compares microbes used (algae, fungi, bacteria and yeast) in biological wastewater treatment in terms of method, species used and removal percentage of COD, BOD, nitrate, phosphate and any related substances.