A systematic and critical review of waste management in micro,small and medium-sized enterprises: future directions for theory and practice

Environmental Science and Pollution Research - Waste management (WM) has received increasing attention in recent years in micro, small, and medium-sized enterprises (MSMEs). However, a...     

Fungal biodegradation and removal of cyanobacteria and microcystins: potential applications and research needs

Environmental Science and Pollution Research - Harmful cyanobacterial blooms (HCB) have severe impacts on marine and freshwater systems worldwide. They cause oxygen depletion and produce potent...     

Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) and phenolic endocrine disrupting chemicals in South and Southeast Asian mussels

A comprehensive monitoring survey for polycyclic aromatic hydrocarbons (PAHs) and phenolic endocrine disrupting chemicals (EDCs) utilizing mussels as sentinel organisms was conducted in South and Southeast Asia as a part of the Asian Mussel Watch project. Green mussel (Perna viridis) samples collected from a total of 48 locations in India, Indonesia, Singapore, Malaysia, Thailand, Cambodia, Vietnam, and the Philippines during 1994–1999 were analyzed for PAHs, EDCs including nonylphenol (NP), octylphenol (OP) and bisphenol A (BPA), and linear alkylbenzenes (LABs) as molecular markers for sewage. Concentrations of NP ranged from 18 to 643 ng/g-dry tissue. The highest levels of NP in Malaysia, Singapore, the Philippines, and Indonesia were comparable to those observed in Tokyo Bay. Elevated concentrations of EDCs were not observed in Vietnam and Cambodia, probably due to the lower extent of industrialization in these regions. No consistent relationship between concentrations of phenolic EDCs and LABs were found, suggesting that sewage is not a major source of EDCs. Concentrations of PAHs ranged from 11 to 1,133 ng/g-dry, which were categorized as “low to moderate” levels of pollution. The ratio of methylphenanthrenes to phenanthrene (MP/P ratio) was >1.0 in 20 out of 25 locations, indicating extensive input of petrogenic PAHs. This study provides a bench-mark for data on the distribution of anthropogenic contaminants in this region, which is essential in evaluating temporal and spatial variation and effect of future regulatory measures.     

Polycyclic Aromatic Hydrocarbon (PAH) Contamination of Surface Sediments from Port Dickson,Malaysia: Distribution,Sources and Ecological Risk Assessment

Distribution and sources of 16 parent polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments from Port Dickson, Malaysia. Total PAHs varied from 481.3 to 976.6 with a mean value of 679.3 ng g^?1 dry weight, which can be classified as moderate level of pollution. The toxic assessment suggested that the PAHs in sediments will not cause immediately adverse biological effects. Both petrogenic and pyrogenic PAHs were recorded in the study area with dominance of pyrogenic. The authors believe that effective monitoring and implementation of environmental regulations have resulted in a tremendous improvement of sediment quality in the Malaysian aquatic ecosystem.     

Molecular docking analysis on antifungal properties of acid condensate produced from palm kernel shell

The rise in the number of fungi that resisted antifungal action is of serious concern nowadays. In this study, the potential of acid condensate (AC) produced from microwave-assisted pyrolysis of palm kernel shell (PKS) was investigated for its antifungal properties through molecular docking evaluation. The phenolic-rich AC was determined for its chemical compositions using the GC–MS analysis where compounds with the highest phenolics content were further evaluated (using the Autodock Tools 1.5.7) for its potential enzymes/protein binding properties. From the GC–MS analysis, catechol, guaiacol and syringol were present at highest percentages. This directly correlates with results obtained from the molecular docking works where all these ligands managed to bind (indicated by H-bond, π-stacking, hydrophobic interaction) with some of the amino acid at the active sites which indicate its potential to inhibit substrate binding of this enzyme. As a conclusion, this study demonstrated the potential use of AC from agricultural biomass such as PKS as a natural-based antifungal agent that can reduce environmental and health impacts.     

Free radical-assisted electrocoagulation processes for wastewater treatment

The combination of electrocoagulation with another process is a promising approach to enhance the removal efficiency of water pollutants. For instance, free radical-assisted electrocoagulation is a new combination showing higher performance. There are different combinations depending on the free radical source. This article reviews free radical-assisted electrocoagulation processes. We discuss electrocoagulation mechanisms; ozone-assisted electrocoagulation processes; advanced oxidation-assisted electrocoagulation processes; and ultrasound-assisted electrocoagulation. We present kinetic models used in free radical-assisted electrocoagulation, scale-up of free radical-assisted electrocoagulation and cost estimation. The major points are: most of the available studies have been done at laboratory scale with synthetic wastewater, and lack holistic and systematic approaches to consider the process complexity. The performance of the combined process is improved, and the removal efficiency is increased especially with ozone-assisted electrocoagulation, which gives a removal efficiency of more than 95%. The use of ultrasound energy with electrocoagulation is advantageous in reducing the problem of electrode passivation.     

Biodegradation of Polycyclic Aromatic Hydrocarbons by Exopolymers Synthesized by Moderately Halophilic Bacteria: Chemical Composition and Functional Properties

Three strains of halophilic bioemulsifier-producing bacteria; Bacillus sp. 2BSG-PDA-16, Bacillus sp. DV2-37 and Bacillus licheniformis ABRII6 were isolated from crude oil polluted water samples. Characteristics of exopolymers produced by these strains in media supplemented with various hydrocarbons instead of glucose were studied. Yield production, chemical composition, emulsifying, rheological and flocculating properties of exopolymers varied according to the strain and the carbon source. The highest amount of exopolymers synthesized by Bacillus sp. 2BSG-PDA-16, Bacillus sp. DV2-37 and B. licheniformis ABRII6 was 11, 18.5 and 12.4 g/l, respectively from media amended with glucose, while the most active emulsifiers were those obtained from media added with crude oil. Furthermore, all exopolymers produced were capable of emulsifying crude oil more efficiently than the three chemical surfactants tested as control (Tween 20, Tween 80 and Triton X-100). Respect to chemical composition, exopolymers produced on hydrocarbons always have lower content of carbohydrates and proteins than exopolymers produced in medium amended with glucose, however they showed higher amounts of uronic acids, sulfates and acetyl residues. The rheological study suggested that the exopolymers have characteristics of the pseudoplastic fluids. Efficiency of bacterial strains to remove PAH seems to agree with their potential applicability in oil bioremediation technology.     

Uptake of heavy metals by some edible vegetables irrigated using wastewater: a preliminary study in Accra, Ghana

The heavy metals (Fe, Zn, Pb, Ni, Cr, Co, and Cd) burden in wastewater, soil, and vegetable samples from a wastewater irrigated farm located at KorleBu, Accra has been investigated. Flame atomic absorption spectrometry after microwave digestion using a combination of HNO₃, HCl, and H₂O₂ (for water), and HNO₃ and HCl (for soil and vegetables). The mean concentrations (in milligrams per kilogram) of heavy metals in the soil samples were in the order of Fe (171?±?5.22)?>?Zn (36.06?±?4.54)?>?Pb (33.35?±?35.62)?>?Ni (6.31?±?8.15)?>?Cr (3.40?±?3.63)?>?Co (1.36?±?0.31)?>?Cd (0.43?±?0.24), while the vegetables were in the order of Fe (183.11?±?161.2)?>?Zn (5.38?±?3.50)?>?Ni (3.52?±?1.27)?>?Pb (2.49?±?1.81)?>?Cr (1.46?±?0.51)?>?Co (0.66?±?0.25)?>?Cd (0.36?±?0.15). The bioconcentration factors suggest environmental monitoring for the heavy metals as follows: Cd (0.828), Cr (0.431), Ni (0.558), Co (0.485), and Fe (1.067). Estimated daily intakes were very low for both children and adults except Fe (0.767 mg/kg/day) in children. The population that consume vegetables from the study area were, however, estimated to be safe based on the results obtained from the health risk index, which were all?<?<1. The sodium absorption ratio according to FAO (1985) classifications indicate that the wastewater in the study area is unsuitable for irrigation purposes.     

Assessment of cylindrospermopsin toxin in an arid Saudi lake containing dense cyanobacterial bloom

This study reports the presence of the cyanobacterial toxin cylindrospermopisn (CYN) and its producer Cylindrospermopsis raciborskii for the first time in Saudi freshwater sources. C. raciborskii was found in Gazan Dam Lake water with two morphotypes (coiled and straight). The appearance and cell density of this species was significantly positively related to high temperature and high ammonium concentrations, and negatively with nitrate and phosphate concentrations in the lake. Intracellular concentrations of CYN (4–173 μg L^?1) were associated with C. raciborskii rather than other cyanobacteria with a maximal value obtained in June 2011, coinciding with the highest bloom of this species (19?×?10⁷ trichome L^?1). CYN cell quotas (0.6–14.6 pg cell^?1) varied significantly along the study period and correlated with most environmental factors. The results of ELISA and liquid chromatography-mass spectrometry proved that the CYN production by strains of this species was isolated from this lake during the present study, with an amount reaching 568 μg g^?1. Extracellular CYN was also detected in cell-free lake water at concentrations 0.03–23.3 μg L^?1, exceeding the drinking water guideline value of 1 μg L^?1 during the Apr–Jul period. As this lake is an important source for drinking and irrigation waters, CYN monitoring should be included in the environmental and health risk assessment plans of these water bodies.     

Discriminant analysis for the prediction of sand mass distribution in an urban stormwater holding pond using simulated depth average flow velocity data

The approach of this paper is to predict the sand mass distribution in an urban stormwater holding pond at the Stormwater Management And Road Tunnel (SMART) Control Centre, Malaysia, using simulated depth average floodwater velocity diverted into the holding during storm events. Discriminant analysis (DA) was applied to derive the classification function to spatially distinguish areas of relatively high and low sand mass compositions based on the simulated water velocity variations at corresponding locations of gravimetrically measured sand mass composition of surface sediment samples. Three inflow parameter values, 16, 40 and 80 m³ s^?1, representing diverted floodwater discharge for three storm event conditions were fixed as input parameters of the hydrodynamic model. The sand (grain size?>?0.063 mm) mass composition of the surface sediment measured at 29 sampling locations ranges from 3.7 to 45.5 %. The sampling locations of the surface sediment were spatially clustered into two groups based on the sand mass composition. The sand mass composition of group 1 is relatively lower (3.69 to 12.20 %) compared to group 2 (16.90 to 45.55 %). Two Fisher’s linear discriminant functions, F ₁ and F ₂, were generated to predict areas; both consist of relatively higher and lower sand mass compositions based on the relationship between the simulated flow velocity and the measured surface sand composition at corresponding sampling locations. F ₁?=??9.405?+?4232.119?×?A???1795.805?×?B?+?281.224?×?C, and F ₂?=??2.842?+?2725.137?×?A???1307.688?×?B?+?231.353?×?C. A, B and C represent the simulated flow velocity generated by inflow parameter values of 16, 40 and 80 m³ s^?1, respectively. The model correctly predicts 88.9 and 100.0 % of sampling locations consisting of relatively high and low sand mass percentages, respectively, with the cross-validated classification showing that, overall, 82.8 % are correctly classified. The model predicts that 31.4 % of the model domain areas consist of high-sand mass composition areas and the remaining 68.6 % comprise low-sand mass composition areas.