Effect of formaldehyde on biofilm activity and morphology in an ultracompact biofilm reactor for carbonaceous wastewater treatment.

The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity.     

Towards a sustainable future: a holistic inquiry of waste management behaviors of Singapore households

ABSTRACT

In 2018, Singapore produced a 7.7 million tonnes of waste, which is a significant amount of waste for a small nation-state. In line with the Sustainable Development Goal (SDGs) targets 11.6 and 12.5 of the 2030 Agenda, which addresses cities’ waste generation and management impacts, we ask the question of why Singapore households are not more proactively engaged in waste minimization, despite the presence of local waste minimization public campaigns. This study is the first known study to comparatively apply and test three major theories – social psychological, social-structural, and sociocultural theories, to explain household waste management behavior in Singapore. A national survey followed by regression analysis of 303 households was conducted. In our findings, we firstly describe current trends in household waste management behaviors. Secondly, we compared each applied theory’s ability to predict households’: (1) reuse and (2) recycling of a variety of household items; and (3) recycling frequency. We obtained partial evidence supporting the role of future-orientedness and environmental identity on householders’ variety reuse and recycling. Social-structural (age cohort x income, education) and situational variables (the convenience thesis), also predicted various waste minimization behaviors. Finally, householders’ knowledge of what is recyclable affected all forms of waste minimization behaviors. In view of the study’s findings, we propose a need for targeted planning and policy interventions for different segments of the Singapore population, and different short- and longer-term measures to initiate and achieve sustained household waste minimization.     

Bioerosion of coral reefs by two Hawaiian parrotfishes: species, size differences and fishery implications

Parrotfishes can be significant bioeroders and sediment producers on coral reefs. We quantified the bioerosion rates of two similarly sized Hawaiian parrotfishes with two different feeding modes (Scarus rubroviolaceus—a scraper and Chlorurus perspicillatus—an excavator). The results showed that feeding modes did not affect bioerosion rates but that bioerosion rates were size dependent, with largest individuals (S. rubroviolaceus 45–54 cm FL) bioeroding up to 380 ± 67 kg ind⁻¹ year⁻¹. The size for onset of bioerosion capabilities for both species was 15 cm. Grazing by the two species consumed 60% of the carbonate production of the fore reef area, suggesting that large parrotfishes in Hawaii are ecologically important bioeroders. As individual large S. rubroviolaceus contributed disproportionately more to bioerosion and sediment production than the equivalent biomass of smaller conspecifics, management strategies designed to retain normal reef bioerosion rates should seek to preserve the historical size structure of S. rubroviolaceus populations and to especially protect the larger size classes.     

Challenges to promoting eco-industry parks in Malaysia: A case study of Rawang Integrated Industrial Park

Journal of Material Cycles and Waste Management - Malaysia is a developing country, and its economic growth has caused the increase in the generation of industrial waste in terms of its volume. The...     

Analysis of Pesticides Using a Polyppyrole Modified Electrode

Electrochemical methods can provide fast, sensitive and sometimes real time detection of pesticides. In the course of this work, a dispersed mercury electrode has been used to detect pesticides electrochemically. The electrode was prepared by depositing a thin mercury film on a glassy carbon disc and then coating a layer of polypyrrole on the disc. The effect of coating thickness on detection sensitivity was studied. A thin mercury film of 0.34 µm dispersed by one cycle polymerization of pyrrole was preferred. The influence of electrolyte, pH and organic solvent content on pesticide response was also investigated. The polypyrrole dispersed mercury electrode (Hg-PPy/GC) was not suitable for a pH above 6 but it can tolerate acetonitrile up to 10% at which concentration the mercury film coated glassy carbon electrode (Hg/GC) failed to response. Methyl parathion, methyl azinphos, parathion and fenitrothion were detected. The sensitivity of the dispersed mercury electrode was similar to a normal thin mercury film electrode in this case. A good response can be obtained for 1 ppm pesticides using fast linear sweeping voltammetry.     

Direct coupling of supercritical fluid extraction-supercritical fluid chromatography for the determination of selected polycyclic aromatic hydrocarbons in aqueous environmental samples

A rapid and simple method is described for the quantitative determination of polycyclic aromatic hydrocarbons in aqueous environmental samples. A microscale on-line supercritical fluid extraction-supercritical fluid chromatography system using carbon dioxide is employed. The extract is analysed using capillary supercritical fluid chromatography with UV detection. Detection was carried out at 254 nm. An extraction efficiency of as high as 91% was obtained for the PAHs.     

Monitoring of bacterial morphology for controlling filamentous overgrowth in an ultracompact biofilm reactor.

This research was part of a study of filamentous growth and control in an ultracompact biofilm reactor (UCBR). Morphologies of biofilm and filamentous bacteria in the UCBR were investigated. Ethanol was used as a substrate and sodium hypochlorite was applied as a toxicant to control filamentous growth. The results indicated that factors such as chemical oxygen demand, surface loading rate, pH, and dissolved oxygen could initiate filamentous overgrowth in the UCBR. Different biofilm and filamentous morphologies in the UCBR were observed under different operational conditions. Chlorination was an effective approach to control filamentous growth during and after biofilm formation. Proper chlorine dosing had no effect on biofilm, but killed filaments. Overdose of chlorine damaged biofilm and caused adverse effects such as low treatment efficiency, media clogging and washout, and biofilm color change in the reactor. Frequent monitoring of the morphologies of filaments and biofilm was needed during chlorination to prevent chlorine overdose.     

The effects of agrochemicals on an aquatic ecosystem : A case study from the Krian River basin,Malaysia

Summary The existing environment of the Krian River basin in Malaysia is not in its natural form for it has been much developed into agricultural lands (105,000 ha). The growing demand for agricultural lands requires further reclamation of swampy forests, which will result in an increased use of fertilisers (estimated 10 percent increase, from 29,500 t to 32,500 t), weedicide, dalapon (estimated 6 percent increase, from 187,620 kg to 199,530 kg) and pesticides, BHC and thiodan/endosulfan (estimated 2 percent increase, from 312 kg to 318 kg).Contrary to belief, the concern over increased levels of nitrogenous fertilisers and pesticides concentrations used in the existing agricultural projects is unfounded. The agrochemicals contribute insignificant amounts of contaminants into the aqueous system. Deleterious deterioration of water quality in the waterways is not apparent. The rich assemblage of icthyofauna comprises 14 freshwater fish species, 21 saltwater-freshwater interface species, like the freshwater prawn and marine fishes that have acclimatised to freshwater conditions, and 28 coastal- marine water fish species, two brackish water penaeids and three molluscs of commercial value. However, if the water quality data are used in isolation to interpret the consequences of large- scale usage of agrochemicals, the conclusion is inadequate and may be misleading. The impact of the flow condition in fields, the localised long-term effects like the fate and spatial distribution on the surrounding media (water, sediments and exposed aquatic life), bio-accumulation and bio-magnification should be considered. Though of no acute toxicity to hardy icthyofauna in the Krian Rice Irrigation basin, lipophilic organochlorines pose health risks to consumers of contaminated fishery products from these Krian rice fields.Dr Siaw-Yang Yap and Dr Hean-Tatt Ong graduated at the University of Malaya (Malaysia) with degrees in Aquatic Ecology and Plant Physiology respectively. Both currently have been involved in water quality criteria and standards development for aquatic life and irrigation uses in Malaysia. They have also contributed to environmental impact assessment projects, commissioned by the Department of Environment, Ministry of Science, Technology and Environment, Malaysia, the Ministry of Agriculture, Malaysia, and others. Dr Yap is an appointed member of the Freshwater Fish Specialist Group, Species Survival Commission/IUCN; she is involved in the "To Maintain Biological Diversity" project, aiming at conservation of genetic diversity of the threatened freshwater fish habitats and species in Asia. Dr Yap is also the specialist for water quality criteria and standards derivation for Malaysia and ASEAN tropical marine environments.     

Metabolites change of Scenedesmus obliquus exerted by AgNPs

With increasing emission of silver nanoparticles (AgNPs) into the environment, it is important to understand the effects of ambient concentration of AgNPs. The biological effects of AgNPs on Scenedesmus obliquus, a ubiquitous freshwater microalgae, was evaluated. AgNPs exerted a minor inhibitory effect at low doses. Non-targeted metabolomic studies were conducted to understand and analyze the effect of AgNPs on algal cells from a molecular perspective. During the 48?hr of exposure to AgNPs, 30 metabolites were identified, of which nine had significant changes compared to the control group. These include d-galactose, sucrose, and d-fructose. These carbohydrates are involved in the synthesis and repair of cell walls. Glycine, an important constituent amino acid of glutathione, increased with AgNP exposure concentration increasing, likely to counteract an increased intracellular oxidative stress. These results provide a new understanding of the toxicity effects and mechanism of AgNPs. These metabolites could be useful biomarkers for future research, employed in the early detection of environmental risk from AgNPs.     

Biofiltration pretreatment for reverse osmosis (RO) membrane in a water reclamation system

Biofouling control is considered as a major challenge in operating membrane systems. A lab-scale RO system was setup at a local water reclamation plant to study the feasibility of using biofiltration as a pretreatment process to control the biofouling. The biological activity in the RO system (feed, product, reject streams) was tested using the standard serial dilution plating technique. Operational parameters such as differential pressure (DP) and permeate flowrate of the system were also monitored. Effects of biofilter on AOC and DOC removals were investigated. Biofiltration was found to be a viable way of assimilable organic carbon (AOC) and dissolved organic carbon (DOC) removals, with removal efficiencies of 40-49% and 35-45% at an empty bed contact time (EBCT) of 30 min. It was also found that using the biofiltration as a pretreatment reduced the rate of biofouling. It took only about 72 h for biofouling to have a significant impact on the performance of the RO membrane, when the system was operated without using biofiltration as pretreatment. There was, however, a five times increase in operational length to more than 300 h when biofiltration was used. This study presented the suitability of the biofilter as an economical and simple way of biofouling control for RO membrane.