A B S T R A C TWater eutrophication is a serious global issue that needs urgent attention. Ammoniacal nitrogen (AN) is present in both domestic and industrial wastewater which acts as one of the main contributors of eutrophication. There is a need to reduce AN to permissible levels as enforced by local authorities before final discharge. Phytoremediation has been recommended as an alternative solution to other conventional physiochemical and biological methods to treat wastewater with high AN content due to its cost-effective, environmental friendly and sustainable characteristics. Water hyacinth (Eichhornia crassipes) is a free-floating macrophyte, which is known as the most noxious weed in the world that shows characteristics of fast growth rate, adaptability to a wide range of environmental conditions and high nutrient uptake capacity. These capabilities contribute to the wide applications of water hyacinth for phytoremediation purpose. This paper provides extensive review on the technical advantages and limitations of phytoremediation as compared to other nitrogen removal technologies, as well as the insight for the development of phytoremediation technology using water hyacinth to treat wastewater with high AN content. This paper also provides fundamental knowledge on the AN removal mechanisms and necessary considerations in selecting the operating conditions of water hyacinth-based phytoremediation system, which may facilitate the design of industrial scale phytoremediation system for effluent treatment. Overall, phytoremediation technology assisted by water hyacinth has been shown to be promising for AN removal, which can be a potential solution in the future for various industries to reduce the AN level in their effluent discharge.

It is noteworthy to highlight that ammonia nitrogen contamination in wastewater has been reported to pose a great threat to the environment. This conventional method of remediating ammonia nitrogen contamination in wastewater applies the packed bed tower technology. Nevertheless, this technology appears to pose several application issues. Over the years, researchers have tested various types of ammonia stripping process to overcome the shortcomings of the conventional ammonia stripping technology. Along this line, the present study highlights the recent development of ammonia stripping process for industrial wastewater treatment. In addition, this study reviews ammonia stripping application for varied types of industrial wastewater and several significant operating parameters. Furthermore, this paper discusses some issues related to the conventional ammonia stripper for industrial treatment application. Finally, this study explicates the future prospects of the ammonia stripping method. This review, hence, contributes by enhancing the ammonia stripping treatment efficiency and its application for industrial wastewater treatment.

Various pre-treatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. The effect of ultrasonic pre-treatment on oil palm empty fruit bunch (OPEFB) fibre prior to acid hydrolysis has been evaluated. The main objective of this study was to determine if ultrasonic pre-treatment could function as a pre-treatment method for the acid hydrolysis of OPEFB fibre at a low temperature and pressure. Hydrolysis at a low temperature was studied using 2% sulphuric acid; 1:25 solid liquid ratio and 100 degrees C operating temperature. A maximum xylose yield of 58% was achieved when the OPEFB fibre was ultrasonicated at 90% amplitude for 45min. In the absence of ultrasonic pre-treatment only 22% of xylose was obtained. However, no substantial increase of xylose formation was observed for acid hydrolysis at higher temperatures of 120 and 140 degrees C on ultrasonicated OPEFB fibre. The samples were then analysed using a scanning electron microscope (SEM) to describe the morphological changes of the OPEFB fibre. The SEM observations show interesting morphological changes within the OPEFB fibre for different acid hydrolysis conditions.

Photooxidative degradation of pre-treated Palm oil mill effluent for removal of chemical oxygen demand, biological oxygen demand and color by UV/TiO 2 system has been investigated in a cylindrical glass photoreactor whose outer surface has been coated with titanium dioxide whereas the UV source has been placed inside the glass tube. The removal of these pollutants indicators has been found to follow pseudofirst-order kinetics and hence the electrical energy per order (E EO ) figure-of-merit is used to calculate approximately the electrical energy efficiency of the advanced oxidation process system. The higher dissolved oxygen (10 mg/L), lower initial concentration (6 mg/L) and acidic medium (pH = 3) have been found favorable to the photocatalytic degradation of palm oil mill effluent.

It is noteworthy that ammoniacal nitrogen contamination in wastewater has reportedly posed a great threat to the environment. Although there are several conventional technologies being employed to remediate ammoniacal nitrogen contamination in wastewater, they are not sustainable and cost-effective. Along this line, the present study aims to highlight the significance of green chemistry characteristics of phytoremediation in nitrogen for wastewater treatment. Notably, ammoniacal nitrogen can be found in many types of sources and it brings harmful effects to the environment. Hence, the present study also reviews the phytoremediation of nitrogen and describes its green chemistry characteristics. Additionally, the different types of wastewater contaminants and their effects on phytoremediation and the phytoremediation consideration in wastewater treatment application and sustainable waste management of harvested aquatic macrophytes were reviewed. Finally, the present study explicates the future perspectives of phytoremediation. Based on the reviews, it can be concluded that green chemistry characteristics of phytoremediation in nitrogen have proved that it is sustainable and cost-effective in relation to other existing ammoniacal nitrogen remediation technologies. Therefore, it can be deduced that a cheaper and more environmental friendly ammoniacal nitrogen technology can be achieved with the utilization of phytoremediation in wastewater treatment.