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Due to rapid depletion of non-renewable energy such as fossil fuel and increasing concerns for green environment, collection of biogas generated from palm oil mill effluent (POME) would be advantageous as source of energy. In this study, empty fruit bunch (EFB) and decanter cake (DC) were used as co-substrates separately with POME to enhance biogas production. Three parameters were evaluated for this experiment, including DC:POME ratio/EFB:POME ratio (in term of volatile solids (VS)), DC/EFB pre-treatment and mixing speed. It was observed that the anaerobic co-digestion (ACD) of DC and POME showed promising reduction in Chemical Oxygen Demand (COD) (>95%), total solids (>74%), VS (>90%), total suspended solids (>90%), volatile suspended solids (>92%) and volatile acid (>83%). The overall improved methane production results show that synergistic effects are observed for both co-substrates, i.e. DC and EFB. EFB was a better co-substrate than DC due to its higher methane yield improvement percentage as compared to mono-digestion of POME. The best ratio obtained for EFB:POME was 0.6:1 with improvement of 2.36 times more than mono-digestion of POME. It is also found that with increasing mixing speed, the methane production can be further improved. Preliminary cost analysis shows that EFB is a promising feedstock for ACD with POME, when considering in terms of technical (i.e. methane yield) and economic efficiencies (i.e. methane productivity and pre-treatment cost). Future works would be focused on the comprehensive optimization of the DC:EFB:POME co-digestion, particularly the improvement of the EFB pre-treatment method and settling characteristics of the digested sludge.

Malaysia is experiencing rapid urbanisation leading to an increase in the demand of energy. The use of renewable energy can satisfy energy demands and mitigate environmental issues such as greenhouse gas (GHG) emission. Biogas produced from anaerobic digestion from different feedstock such as food waste (FW), palm oil mill effluent (POME), garden waste (GW), landfill, sewage sludge (SS) and animal manure can be utilised to reduce the need of fossil fuel. This review paper will focus on the current biogas technologies, their scalability and socio-economic analysis on biowastes to energy in Malaysia. If all FW generated in Malaysia (approximately 15,000 tonnes per day) could be converted to energy, it has a potential to replace fossil fuel totally, as it produces 10 times more than the annual requirement of energy. Consequently, there is a significant advantage obtained from offsetting huge amounts of GHG emissions that would otherwise be contributing to the global warming effect. Several issues and challenges have been identified for the scale-up of laboratory scale to industrial scale where parameters including pH, temperature, organic loading rate (OLR), hydraulic retention time (HRT) and mixing rate must be treated carefully. The socio-economic survey conducted as part of this study has revealed the strong acceptability of this technology and the readiness of the population in Malaysia to contribute and be part of this effort. However, the survey has also identified the limitations of the sorting and preparation facilities of food waste segregation for potential biogas generation.

Ecological floating bed (EFB) has become the preferred technology due to its reputation of green economy, convenience, and efficiency in treating eutrophic landscape water. Based on the statistical analysis of abundant literatures, this paper systematically summarizes the component elements, design parameters, purification mechanism, purification ability, strengthening methods and the correlations among various parameters of EFB, and points out some issues existing in the current research and applications. The results show that the coverage of 5% ~ 38% and water depth of 60 ~ 110 cm should be recommended for EFB design. The microbial transformation-sedimentation contributes mostly to the removal of pollutant, leading to the contribution rate of 51.9% ± 26.4% to nitrogen (N) removal and 50.8% ± 20.4% to phosphorus (P) removal in water respectively. Meanwhile, the average purification abilities of EFB for carbon (C), N and P in water are 4.59 ± 3.82, 0.43 ± 0.35 and 0.04 ± 0.04 g m -2 d -1 respectively. The purification effect is relatively superior when the initial concentration of C, N and P in water is close to C: N: P = 115: 11: 1. In order to enhance the EFB purification efficiency, the methods of artificial aeration, biological chain extension, functional filler introduction, and composite EFB construction can be used. Furthermore, the purification ability of EFB per unit area is correlated positively with water temperature and initial pollutant concentration (r ≥ 0.577, p < 0.01), and correlated negatively with EFB coverage (r ≤ -0.598, p < 0.01). The future research of EFB should focus on enhancing its purification efficiency and seasonal adaptability, studying the mechanism of algae inhibition by allelochemicals, and exploring the harvesting management and resource utilization of plants. This paper provides more reasonable design parameters, feasible management strategies and prospective research directions for environmental managers and researchers who would like to adopt EFB to purify eutrophic landscape water., (Copyright © 2019. Published by Elsevier B.V.)

In consideration of severe eutrophication of scenic water caused by pollutants released from sediments in summer, calcium peroxide (CaO 2 ) was adopted as the slow release peroxide to improve the water quality in a field experiment of 600 m 2 . The effect of CaO 2 on the overlying water, interstitial water, sediment, and sediment microorganisms of scenic water was studied. Results for two months indicated that the dissolved oxygen (DO) concentration of the overlying water in the test zone was 3.78 times that in the control zone; the oxidation-reduction potential (ORP) in the overlying water and sediment increased significantly (p = 0.002 and p = 0). Meanwhile, CaO 2 could effectively inhibit the release of nitrogen (N) and phosphorus (P) from the sediment and could obviously reduce the concentrations of N and P in the overlying water by enhancing the microbiological action. Moreover, the average concentrations of total nitrogen and total phosphorus in the overlying water of the test zone were 46.27% and 50.51% of those in control zone, respectively, and the concentrations of N and P in the interstitial water decreased during the entire experiment. In addition, CaO 2 decreased the relative abundance of anaerobic bacteria in the sediment, whereas it increased that of aerobic bacteria and promoted the appearance of the functional bacteria, such as Nitrospirae and Thermodesulfoba. In conclusion, CaO 2 can improve the DO and ORP in the eutrophic water effectively and change the microbial community in the sediment to a certain extent, thereby controlling the pollutants released from the sediment and reducing the N and P concentrations in the overlying water. Thus, CaO 2 can effectively realize the purification and restoration of the severely eutrophic scenic water., (Copyright © 2018. Published by Elsevier B.V.)

A floating bed (FB) system vegetated with calamus, iris, lythrum, and Hydrocotyle vulgaris, and a strengthened FB (SFB) system with zeolite and sponge iron as fillers were simultaneously applied to purify urban landscape water in different zones. The urban landscape water, an artificial lake of approximately 326m 2 , was supplied with reclaimed water during a six-month experiment. Results indicated that the concentrations of nitrogen (N) and phosphorus (P) in the SFB zone (SFBZ) were significantly lower than those in the control zone (CZ) and the FB zone (FBZ) after six months of operation. The average removal efficiencies (AREs) in the SFBZ, FBZ and CZ were 89.98%, 77.39% and 56.37%, respectively, for ammonia nitrogen (NH 4 + -N); 92.49%, 79.55% and 47.85%, respectively, for phosphate (PO 4 3- -P). Meanwhile, the average concentration of Chlorophyll a and the algae density in SFBZ during the experiment were 12.54μg/L and 1.31×10 4 cells/mL, which were lower, obviously, than those in the FBZ and CZ. Moreover, the contribution rates analysis of nutrient removal exhibited that the plant absorption in the removal of N and P occupied 27.85% and 26.36%, whereas the filler adsorption occupied 7.93% and 11.93%, respectively, in the SFB. Thus, the water quality of the artificial lake was improved greatly by the SFB which hybridized fillers and FB together. Finally, it was found that the AREs of NH 4 + -N and PO 4 3- -P in the SFBZ could reach 73.93% and 84.56%, approximately 1.39 and 1.41 times that of the FBZ during the winter. Therefore, the application of an SFB can keep a stable water quality in urban landscape water and avoid the lower removal rate of an FB at low-temperature. In summary, the SFB could effectively improve the water quality of urban landscape water supplied with reclaimed water even in winter., (Copyright © 2017. Published by Elsevier B.V.)