Water quality studies in Kranji catchment, Singapore: use of organic tracers and polyethylene devices for identifying potential sewage sources

The objective of this study was to identify organic compounds that could serve as indicators of potential human fecal contamination sources to the Kranji Reservoir in Singapore and could be used as confirmation indicators along with bacteria indicators. The compounds chosen as potential tracers were nonylphenol (NP) and nonylphenol ethoxylates (NPEs), as these are indicative of sewage and have been found at measurable concentrations in rivers and streams elsewhere in Asia. Polyethylene devices (PEDs) were used as passive samplers to measure NP and NPEs in stormwater drains in Kranji Catchment, deployed in areas of different land use in order to obtain an overview of concentration ranges across the catchment and provide an indication of where and why these compounds could be found. Laboratory results showed that NP and NPEs were present in non-residential areas and preliminary modeling of corresponding water concentrations indicates potentially risky concentrations of NP in the water in some stormwater drains. More information is needed on detergents in Singapore to further evaluate using NPEs as sewage indicators. Future studies should be done to confirm concentrations in Kranji Catchment water to verify if there is a risk to the ecosystem's health as NP and NPEs are known endocrine disruptors.

Nano- and Micro-Structural Evolution of UHMWPE by Ion Beam

It is important to produce uniform nano-patterns with no possibility of surface exfoliation on polyethylene devices used in medical and in aerospace industry. We studied the change in the surface morphology of polyethylene at nanoscale using MeV ion beam. We have investigated the change in the surface morphology before and after ion bombardment. We have made an attempt to change the morphology to produce a uniform surface with reduced cracks and reduced granularity. For this process we have chosen ultra-high-molecular-weight polyethylene (UHMWPE). Coupons of these materials were exposed to various fluences of MeV Ag+ ions. The surface morphology and the change in the chemical structure were studied using scanning micro Raman, FTIR and AFM.