Determination of the archaeal and bacterial communities in two-phase and single-stage anaerobic systems by 454 pyrosequencing

2-Phase anaerobic digestion (AD), where the acidogenic phase was operated at 2 day hydraulic retention time (HRT) and the methanogenic phase at 10 days HRT, had been evaluated to determine if it could provide higher organic reduction and methane production than the conventional single-stage AD (also operated at 12 days HRT). 454 pyrosequencing was performed to determine and compare the microbial communities. The acidogenic reactor of the 2-phase system yielded a unique bacterial community of the lowest richness and diversity, while bacterial profiles of the methanogenic reactor closely followed the single-stage reactor. All reactors were predominated by hydrogenotrophic methanogens, mainly Methanolinea. Unusually, the acidogenic reactor contributed up to 24% of total methane production in the 2-phase system. This could be explained by the presence of Methanosarcina and Methanobrevibacter, and their activities could also help regulate reactor alkalinity during high loading conditions through carbon dioxide production. The enrichment of hydrolytic and acidogenic Porphyromonadaceae, Prevotellaceae, Ruminococcaceae and unclassified Bacteroidetes in the acidogenic reactor would have contributed to the improved sludge volatile solids degradation, and ultimately the overall 2-phase system''s performance. Syntrophic acetogenic microorganisms were absent in the acidogenic reactor but present in the downstream methanogenic reactor, indicating the retention of various metabolic pathways also found in a single-stage system. The determination of key microorganisms further expands our understanding of the complex biological functions in AD process.     

Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000–2013)

Constructed wetlands (CWs) have been successfully used for treating various wastewaters for decades and have been identified as a sustainable wastewater management option for developing countries. With the goal of promoting sustainable engineered systems that support human well-being but are also compatible with sustaining natural (environmental) systems, the application of CWs has become more relevant. Such application is especially significant for developing countries with tropical climates, which are very conducive to higher biological activity and productivity, resulting in higher treatment efficiencies compared to those in temperate climates. This paper therefore highlights the practice, applications, and research of treatment wetlands under tropical and subtropical conditions since 2000. In the present review, removal of biochemical oxygen demand (BOD) and total suspended solid (TSS) was shown to be very efficient and consistent across all types of treatment wetlands. Hybrid systems appeared more efficient in the removal of total suspended solid (TSS) (91.3%), chemical oxygen demand (COD) (84.3%), and nitrogen (i.e., 80.7% for ammonium (NH)₄-N, 80.8% for nitrate (NO)₃-N, and 75.4% for total nitrogen (TN)) as compared to other wetland systems. Vertical subsurface flow (VSSF) CWs removed TSS (84.9%), BOD (87.6%), and nitrogen (i.e., 66.2% for NH₄-N, 73.3% for NO₃-N, and 53.3% for TN) more efficiently than horizontal subsurface flow (HSSF) CWs, while HSSF CWs (69.8%) showed better total phosphorus (TP) removal compared to VSSF CWs (60.1%). Floating treatment wetlands (FTWs) showed comparable removal efficiencies for BOD (70.7%), NH₄-N (63.6%), and TP (44.8%) to free water surface (FWS) CW systems.     

Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000-2013)

Constructed wetlands(CWs) have been successfully used for treating various wastewaters for decades and have been identified as a sustainable wastewater management option for developing countries. With the goal of promoting sustainable engineered systems that support human well-being but are also compatible with sustaining natural(environmental)systems, the application of CWs has become more relevant. Such application is especially significant for developing countries with tropical climates, which are very conducive to higher biological activity and productivity, resulting in higher treatment efficiencies compared to those in temperate climates. This paper therefore highlights the practice,applications, and research of treatment wetlands under tropical and subtropical conditions since 2000. In the present review, removal of biochemical oxygen demand(BOD) and total suspended solid(TSS) was shown to be very efficient and consistent across all types of treatment wetlands. Hybrid systems appeared more efficient in the removal of total suspended solid(TSS)(91.3%), chemical oxygen demand(COD)(84.3%), and nitrogen(i.e.,80.7% for ammonium(NH)4-N, 80.8% for nitrate(NO)3-N, and 75.4% for total nitrogen(TN))as compared to other wetland systems. Vertical subsurface flow(VSSF) CWs removed TSS(84.9%), BOD(87.6%), and nitrogen(i.e., 66.2% for NH4-N, 73.3% for NO3-N, and 53.3% for TN)more efficiently than horizontal subsurface flow(HSSF) CWs, while HSSF CWs(69.8%)showed better total phosphorus(TP) removal compared to VSSF CWs(60.1%). Floating treatment wetlands(FTWs) showed comparable removal efficiencies for BOD(70.7%),NH4-N(63.6%), and TP(44.8%) to free water surface(FWS) CW systems.     

A global health problem caused by arsenic from natural sources

Arsenic is a carcinogen to both humans and animals. Arsenicals have been associated with cancers of the skin, lung, and bladder. Clinical manifestations of chronic arsenic poisoning include non-cancer end point of hyper- and hypo-pigmentation, keratosis, hypertension, cardiovascular diseases and diabetes. Epidemiological evidence indicates that arsenic concentration exceeding 50 microg l(-1) in the drinking water is not public health protective. The current WHO recommended guideline value for arsenic in drinking water is 10 microg l(-1), whereas many developing countries are still having a value of 50 microg l(-1). It has been estimated that tens of millions of people are at risk exposing to excessive levels of arsenic from both contaminated water and arsenic-bearing coal from natural sources. The global health implication and possible intervention strategies were also discussed in this review article.     

新型抗氧化膜材料PSAA的研制

对聚亚磺酰氨基酰胺(PSAA)作为新型抗氧化反渗透膜材料的可能性,以及聚合条件和成膜条件对膜性能的影响作了初步研究。     

Fatigue Life Behaviour of Glass/Kenaf Woven-Ply Polymer Hybrid Biocomposites

Investigation on the fatigue life of hybrid composites is critical to extend their applications and acceptance among industries; however, there is a lack of research focus on fatigue performance of the hybrid composite. In this study, the fatigue life of glass/kenaf woven-ply hybrid composite with thermoplastic and thermoset polymer matrix was investigated. Hybrid composites consist of two different fibre configurations: kenaf/glass/kenaf and glass/kenaf/glass. Thermoplastic hybrid composites were manufactured through the hot press moulding compression method, while thermoset hybrid composites were fabricated through the vacuum-assisted resin infusion method. The tensile strength and fatigue strengths of the kenaf/glass/kenaf composite have been identified to be significantly lower than those of the glass/kenaf/glass composite regardless of the types of matrix used. However, thermoplastic-based kenaf/glass/kenaf composites are less fatigue sensitive compared to glass/kenaf/glass composites; however, this phenomenon is vice versa for thermoset composites due to the epoxy matrix, which limits the stiffening effect in natural fibres.     

Heavy Metal Contents and Magnetic Properties of Playground Dust in Hong Kong

This study examined the levels of seven heavy metals (namelyzinc, copper, cadmium, chromium, lead, manganese and iron) andtheir associations with magnetic properties in playground dustof Hong Kong. Results showed that the playground dust containedhigh concentrations of Zn (mean = 1883 g g^-1), Cu(mean = 143 g g^-1) and Cr (mean = 263 g g^-1).Qualitative examination of dust samples under microscope indicated local traffic as one of the important pollutant sources. Magnetic measurements indicated that these anthropogenicpollutants mainly consisted of coarse-grained multidomain (MD) ferrimagnetic minerals. Superparamagnetic (SP), stable single domain (SSD) ferrimagnetic grains and non-ferrimagnetic mineralswere present in relatively small amounts. Significant correlations between heavy metals and various magnetic parametersindicated a strong affinity of heavy metals to magnetic minerals hence pointed out the potential of magnetic properties for simpleand rapid proxy indications of heavy metal pollution in playground dust.     

Evaluation of in situ catalysed hydrogen peroxide propagation (CHP) for phenanthrene and fluoranthene removals from soil and its associated impacts on soil functionality

Extensive contamination of soils by highly recalcitrant contaminants such as polycyclic aromatic hydrocarbons (PAHs) is an environmental problem arising from rapid industrialisation. This work focusses on the remediation of soil contaminated with 3- and 4-aromatic ring PAHs (phenanthrene (PHE) and fluoranthene (FLUT)) through catalysed hydrogen peroxide propagation (CHP). In the present work, the operating parameters of the CHP treatment in packed soil column was optimised with central composite design (H₂O₂/soil 0.081, Fe³⁺/soil 0.024, sodium pyrophosphate (SP)/soil 0.024, pH of SP solution 7.73). The effect of contaminant aging on PAH removals was also investigated. Remarkable oxidative PAH removals were observed for the short aging and extended aging period (up to 86.73 and 70.61 % for PHE and FLUT, respectively). The impacts of CHP on soil biological, chemical and physical properties were studied for both spiked and aged soils. Overall, the soil functionality analyses after the proposed operating condition demonstrated that the values for soil respiration, electrical conductivity, pH and iron precipitation fell within acceptable limits, indicating the compatibility of the CHP process with land restoration.     

Runoff and drainage losses of atrazine, metribuzin, and metolachlor in three water management systems

Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.     

Strategic environmental assessment in Hong Kong

This review examines the development and application of strategic environmental assessment (SEA) process in the planning framework of Hong Kong. Two strategic planning case studies are evaluated within the context of SEA, namely the Territorial Development Strategy Review (TDS Review) and the Third Comprehensive Transport Study (CTS-3). Rapid population growth and urbanisation in Hong Kong, coupled with a historic lack of planning controls and inherent conflicts between government departments have been major obstacles to achieving sustainable development in the territory. Despite these challenges, Hong Kong was one of the first Asian countries to apply SEA to major development plans, where the implementation of the 'SUSDEV 21' study on sustainable development has demonstrated the government's commitment towards integrated environmental protection. The application of SEA has provided decision-makers with key information on potential environment impacts arising from proposed developments, resulting in greater accountability and transparency in the decision-making process. SEA in Hong Kong has also prompted an increased level of environmental awareness and co-operation between government departments and agencies responsible for the management of Hong Kong's natural and urban environments. However, the application of SEA in Hong Kong continues to have notable limitations. SEA needs to evolve beyond its current sectoral application to examine ways in which development decisions can not only pre-empt and prevent environmental damage, but also positively enhance and restore existing natural resources. Current land use plans and transportation strategies still largely determine the pattern of development in the near future without adequate longer-term environmental cost-benefit analysis. Sustainable development includes environmental, social and economic considerations, and these inter-related elements need be suitably balanced. SEA is not a means to obstruct development in Hong Kong, but should be recognised for its inherent socio-economic and ecological value, and fully integrated with the decision-making process. Whilst it is admirable that Hong Kong has taken positive steps in this direction, it is now an opportune moment for the government to have the foresight and tenacity to create a sustainable development framework for Hong Kong into the future.