Rapid urbanization, population explosion and climate change have threatened water security globally, regionally and locally. While there are many ways of addressing these problems, one of the innovative techniques is the recent employment of Sustainable Urban Drainage Systems (SUDS) which include rainwater harvesting systems (RWHS). Therefore, this paper reviews the design and component of two types of RWHS, the namely roof harvesting system (RHS) and the pond harvesting system (PHS). The performance in terms of quantity and quality of collected rainwater and energy consumption for RWHS with different capacities were evaluated, as well as the benefits and challenges particularly in environmental, economic and social aspects. Presently, the RHS is more commonly applied but its effectiveness is limited by its small scale. The PHS is of larger scale and has greater potentials and effectiveness as an alternative water supply system. Results also indicate the many advantages of the PHS especially in terms of economics, environmental aspects and volume of water harvested. While the RHS may be suited to individual or existing buildings, the PHS has greater potentials and should be applied in newly developed urban areas with wet equatorial climate.

Flooding is a frequent, naturally recurring phenomenon worldwide that can become disastrous if not addressed accordingly. This paper aims to evaluate the impacts of land use change and climate change on flooding in the Segamat River Basin, Johor, Malaysia, with 1D–2D hydrodynamic river modeling, using InfoWorks Integrated Catchment Modeling (ICM). The study involved the development of flood maps for four different scenarios: (1) future land use in 2030; (2) the impacts of climate change; (3) three mitigation strategies comprising detention ponds, rainwater harvesting systems (RWHSs), and permeable pavers; and (4) a combination of these three mitigation strategies. The obtained results show increases in the flood peaks under both the land use change and climate change scenarios. With the anticipated increase in development activities within the vicinity up to 2030, the overall impact of urbanization on the extent of flooding would be rather moderate, as the upper and middle parts of the basin would still be dominated by forests and agricultural activities (approximately 81.13%). In contrast, the potential flood-inundated area is expected to increase from 12.25% to 16.64% under storms of 10-, 50-, 100-, and 1000-year average recurrence intervals (ARI). Interestingly, the simulation results suggest that only the detention pond mitigation strategy has a considerable impact on reducing floods, while the other two mitigation strategies have less flood reduction advantages for this agricultural-based rural basin located in a tropical region.

Constructed wetlands are an affordable and reliable green alternative to conventional mechanical systems for treating domestic sewage. This study investigates the potential of 14 tropical wetland plant species for removing heavy metals from domestic sewage through the bioconcentration factor (BCF), translocation factor (TF), enrichment factor (EF), and geoaccumulation index (I_geo) using batch mesocosm studies. Plants with BCF > 1 and TF > 1 are classified as phytoextractors, while species with BCF > 1 and TF < 1 are phytostabilisers. The results indicate that 11 out of 14 species are magnesium phytostabilisers, 10 are calcium phytoextractors, and no plant species demonstrate ferrum phytoextraction properties. As for manganese phytoremediation, only three species depicted phytoextraction and phytostabilisation properties. The enrichment factor (EF) for all of the studied metals with ferum as a reference metal in all of the soil samples decreased after the phytoremediation of domestic sewage experiments, indicating depletion to mineral enrichment (EF < 2). All of the soil samples are generally classified as uncontaminated based on I_geo indices. Based on the factors and indices, it is suggested that the plants may have facilitated heavy metal removal from domestic sewage through uptake into the plant tissues from the roots.

Over the years, the emergence of pesticides practice has prevailed to be the most intricate environmental turmoil amongst the scientific community. Specifically, pesticides constitute an accumulative, persistent and detrimental impact towards the survival of flora, fauna and environmental matrix. This has inspired a developing research with a variety of treatment technologies. Adsorption is recognized as the most efficient and promising approach, due to the ease of operation, simplicity of design, insensitivity to the toxic substances and superior capability for removing a broad range of pollutants. Its diverse applications, however, are retarded by the high cost of adsorbents and difficulties associated with regeneration. Montmorillonite and its derivatives, a unique group of under-utilized clay-based minerals has been proposed to be a suitable candidate for the treatment of contaminated wastewater. It plays a key role as the natural scavenger of pesticides, due to the abundantly availability, large specific surface area and high adsorptive and ion exchange properties. This paper describes the origin, physical, chemical and physicochemical properties of natural montmorillonite. The preparation procedure, reusability, commercial product and economical evaluation are highlighted. The specific classification, environmental and health implication of organo-pesticide are discussed. The revolution of montmorillonite-assisted adsorption process for the remediation of organo-pesticide was summarized. Additionally, the characterizations, surface chemistry and mechanism investigation are outlined.

In this work, an atmospheric water generator (AWG) system called the medium-scale AWG (MSAWG) was designed, fabricated, and tested in Universiti Sains Malaysia (USM) under the outdoor tropical climate conditions of Malaysia to investigate the amount of fresh water production in successive periods of 24 h. The MSAWG consisted of 18 thermoelectric cooler (TEC) units, 18 internal finned heat sinks, 18 external finned heat sinks, 18 direct current (DC) cooling fans, an air-conditioner mesh air filter, and an axial ventilation fan. It was found from the results that the hourly values of water production of MSAWG were proportional to the hourly rates of relative humidity, but they were inversely affected by the corresponding hourly values of the ambient temperature. Night-time and early morning were the most effective times to produce the highest amount of fresh water from Malaysia’s atmosphere using MSAWG, as the increase in the rates of relative humidity and the decrease in the values of ambient temperature occurred over these periods. Based on the varied hourly rates of relative humidity with the ranges between the minimum rate of 55% and maximum rate of 85%, an equation of Y = 0.2285X + 36.675 with R² of 0.9404 was achieved from the 48 h experimental work to estimate the water production of MSAWG in Malaysia, where Y and X were indicated as the rate of relative humidity and the value of water production, respectively, in this equation. In conclusion, the MSAWG produced a consecutive cumulative water volume of 3.432 and 6.997 L experimentally in the periods of 24 and 48 h, respectively. The estimated cost per liter for MSAWG was USD 0.466. Some water quality parameters of the fresh water produced by MSAWG were analysed in the laboratory, which showed that they met the World Health Organization (WHO) drinking water standards. Therefore, MSAWG can be employed as a sustainable alternative to generate annual daily fresh water from Malaysia’s tropical atmosphere and aid in mitigating the problem of unpredicted water shortage in the country.

Subsurface perforated pipes drain infiltrated stormwater runoff while attenuating the peak flow. The Manning roughness coefficient (n) was identified as a fundamental parameter for estimating roughness in various subsurface channels. Hence, in this work, the performance of a six-row non-staggered sand-slot perforated pipe as a sample of the subsurface drainage is investigated experimentally in a laboratory flume at Universiti Sains Malaysia (USM) aimed at determining the Manning roughness coefficients (n) of the pipe and assessing the relationship between the Manning’s n and the hydraulic parameters of the simulated runoff flow under the conditions of the tailgate channel being opened fully (GFO) and partially (GPO), as well as the pipe having longitudinal slopes of 1:750 and 1:1000. Water is pumped into the flume at a maximum discharge rate of 35 L/s, and the velocity and depth of the flow are measured at nine points along the inner parts of the pipe. Based on the calculated Reynolds numbers ranging from 38,252 to 64,801 for both GFO and GPO conditions, it is determined that most of the flow in the perforated pipe is turbulent, and the calculated flow discharges and velocities from the outlets under GFO are higher than the flow and velocity rates under GPO with similar pipe slopes of 1:750 and 1:1000. The Manning coefficients are calculated at nine points along the pipe and range from 0.004 to 0.009. Based on the ranges of the calculated Manning’s n, an inverse linear relationships between the Manning coefficients and the flow velocity under GFO and GPO conditions are observed with the R² of 0.975 and 0.966, as well as 0.819 and 0.992 resulting from predicting the values of flow velocities with the equations v = ((0.01440 − n)/0.009175), v = ((0.01330 − n)/0.00890), v = ((0.02007 − n)/0.01814), and v = ((0.01702 − n)/0.01456) with pipe slopes of 1:750 and 1:1000, respectively. It is concluded that since the roughness coefficient (Manning’s n) of the pipe increases, it is able to reduce the flow velocity in the pipe, resulting in a lower peak of flow and the ability to control the quantity of storm water in the subsurface urban drainages.