Wash water in waterworks: contaminants and process options for reclamation

Reclamation of clean water from filter backwash water was studied through pilot-scale experiments.The pilot plant consisted of clarification,sand-filtration,and ultrafiltration modules in sequence,with a provision to bypass the sand filter.Clean water that conformed to World Health Organization (WHO) guidelines on Potable Quality was reclaimed.Turbidity,aluminum and iron were found to be critical contaminants in process selection and design.Clarification,followed by sand filtration,was found to be the minim...     

Polybrominated diphenyl ethers and organochlorine pesticides in human breast milk from Massachusetts, USA

Concentrations of polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs; DDTs, HCHs, CHLs, and HCB) were measured in human breast milk samples collected across Massachusetts, USA, in 2004. Seventeen PBDE congeners were found in the samples, ranging in concentration from 0.06 to 1910 ng g(-1) lipid wt. BDE-47 (2,2',4,4'-tetraBDE), BDE-99 (2,2',4,4',5-pentaBDE), and BDE-100 (2,2',4,4',6-pentaBDE) were the major congeners detected in breast milk samples. Overall mean (+/-SD) concentrations of DDTs, HCHs, CHLs, and HCB were 64.5 +/- 75, 18.9 +/- 19, 32.4 +/- 36, and 2.3 +/- 2.2 ng g(-1) lipid wt, respectively. Concentrations of PBDEs were strongly correlated with concentrations of OCPs in the samples. Based on the concentrations of organohalogens and the intake rates of breast milk by infants in the United States, daily ingestion rates of contaminants were calculated. The median ingestion rates for PBDEs, HCHs, DDTs, CHLs, and HCB were 4.0, 212, 141, 44, and 5.79 ng kg(-1) body wt day(-1), respectively. The estimated daily intake of organohalogens by infants was compared with threshold reference values suggested by the United States Environmental Protection Agency (USEPA) and the Agency for Toxic Substances and Disease Registry (ATSDR), for calculation of hazard quotients (HQs). HQs for individual organohalogens and the sum of HQ for all organohalogens were calculated as HQ indices (HQI). The results suggest that one or more of the contaminants analyzed in this study exceeded the threshold reference values in at least 26% of the breast milk samples.     

Photocatalysis: Preface

<正>A recent search of the keyword"Photocatalysis"in the CAS Sci Finder?database shows that at least 5,000 articles on this topic have been published each year from 2014 to2016.It is expected that even more articles on this topic will be published in the foreseeable future.These data indicate the importance of"Photocatalysis"in the field.The first     

Advances in photocatalytic disinfection of bacteria: Development of photocatalysts and mechanisms

Photocatalysis has attracted worldwide attention due to its potential in solar energy conversion. As a “green” advanced oxidation technology, it has been extensively used for water disinfection and wastewater treatment. This article provides a review of the recent progress in solar energy-induced photocatalytic disinfection of bacteria, focusing on the development of highly efficient photocatalysts and their underlying mechanisms in bacterial inactivation. The photocatalysts are classified into TiO₂-based and non-TiO₂-based systems, as TiO₂ is the most investigated photocatalyst. The synthesis methods, modification strategies, bacterial disinfection activities and mechanisms of different types of photocatalysts are reviewed in detail. Emphasis is given to the modified TiO₂, including noble metal deposition, non-metal doping, dye sensitization and composite TiO₂, along with typical non-TiO₂-based photocatalysts for bacterial disinfection, including metal oxides, sulfides, bismuth metallates, graphene-based photocatalysts, carbon nitride-based photocatalysts and natural photocatalysts. A simple and versatile methodology by using a partition system combined with scavenging study is introduced to study the photocatalytic disinfection mechanisms in different photocatalytic systems. This review summarizes the current state of the work on photocatalytic disinfection of bacteria, and is expected to offer useful insights for the future development in the field.     

Current status of coastal zone issues and management in China: a review

This paper identifies and examines social-economic and environmental issues recently emerged in China's coastal zone. Evaluation of management scheme and progress in perspectives of coordinated legislation, institutional arrangement, public participation, capacity building, and scientific research (mainly coastal planning and functional zoning) in China's coastal zone are made. The Chinese government has made a significant effort in developing legislation for the coastal zone. Jurisdictional and zoning boundaries, and allocating use rights for coastal and marine resources have been established. State Oceanic Administration is the leading agency responsible for China's ocean policymaking and overall management of ocean and coastal affairs. A demonstrated project for integrated coastal management in Xiamen has been implemented, and is characterized as "decentralization" approach in decision-making process. In view of the above, comprehensive coastal management in China is a big challenge, facing with many difficulties. Finally, recommendations are raised for tackling these issues for China's coastal zone management.     

An expert system for water quality modelling

The RAISON-micro (Regional Analysis by Intelligent System ON a micro-computer) expert system is being used to predict the effects of mine effluents on receiving waters in Ontario. The potential of this system to assist regulatory agencies and mining industries to define more acceptable effluent limits was shown in an initial study. This system has been further developed so that the expert system helps the model user choose the most appropriate model for a particular application from a hierarchy of models. The system currently contains seven models which range from steady state to time dependent models, for both conservative and nonconservative substances in rivers and lakes. The menu driven expert system prompts the model user for information such as the nature of the receiving water system, the type of effluent being considered, and the range of background data available for use as input to the models. The system can also be used to determine the nature of the environmental conditions at the site which are not available in the textual information database, such as the components of river flow. Applications of the water quality expert system are presented for representative mine sites in the Timmins area of Ontario.     

粉煤灰钝化污泥对土壤理化性质及玉米重金属累积的影响

通过温室盆栽试验研究施用不同量及不同比例粉煤灰钝化污泥对土壤理化性质、玉米生长和重金属累积的影响。试验结果表明：施用粉煤灰钝化污泥能显著提高酸性土壤的pH值和Ca、Mg、B的含量,降低土壤的电导率和重金属的有效性。施用合适比例和合适量的粉煤灰钝化污泥能明显改善土壤的物理性质,增加土壤的N、P养分,并能显著提高玉米地上部干物重。10％和5％是高施用量和低施用量时合适的粉煤灰加入比例,施用此比例粉煤灰钝化污泥时,玉米的地上部干物重显著高于施用化肥的对照土壤或于之相当,且没有硼和重金属的毒害。     

Survival strategies of plants associated with arbuscular mycorrhizal fungi on toxic mine tailings

A field survey of metal concentrations and arbuscular mycorrhizal (AM) components of plants growing on five mining sites was conducted in Chenzhou City, Hunan Province, Southern China and a control site in Hong Kong. Significant differences were observed in the average concentrations of total heavy metals (Pb, Zn, Cu, Cd) and one metalloid (As) in contaminated soils compared with the control site. Gramineae and Compositae were the dominant plant families growing on mine tailings, with Chrysanthemum moritolium (common chrysanthemum), Cynodon dactylon (Bermuda grass), Miscanthus florodulus (Sword grass) and Pteris vittata (Ladder brake fern) commonly found at all sites. AM fungal colonization was detected in most of the plants. Comparing the four common plant species, three components of mycorrhizal colonization (arbuscules, vesicles and coiled hyphae) were found in the roots of C. dactylon and P. vittata growing at Do Shun Long (DSL) mine site. Concentrations of As in fronds were 24-fold higher than in roots of P. vittata with the highest mycorrhizal colonization rate (73%) among all sampling sites. Extensive mycorrhizal colonization (85%) was also recorded in the roots of C. dactylon with As accumulation 57 times higher than in shoots. The four common plants found in metal contaminated sites had developed different strategies for survival in the contaminated sites with the aid of indigenous AM fungi.     

Distribution characteristics of fluoride and aluminum in soil profiles of an abandoned tea plantation and their uptake by six woody species

Distribution characteristics of fluoride (F) and aluminum (Al) in soil profiles of an abandoned tea plantation in Hong Kong and their uptake by six woody species namely Camellia sinensis, Melastoma affine, Sterculia lanceolata, Ardisia crenata, Acacia formosa and Machilus thunbergii were investigated. C. sinensis accumulated both F (656 mg/kg in the leaves) and Al (8910 mg/kg in the leaves). M. Affine only accumulated Al (9932 mg/kg in the leaves), while S. lanceolata, A. crenata, A. formosa and M. Thunbergii were Al (26-115 mg/kg in the leaves) and F (20-25 mg/kg in the leaves) excluders. Water-soluble F and Al contents accumulated in surface soils (especially 0-3 cm) and decreased with depth along soil profiles: A layers (2.0 +/- 0.6 and 31 +/- 5.8 mg/kg) > B layers (1.5 +/- 0.2 and 27 +/- 3.5 mg/kg) > C layers (1.3 +/- 0.2 and 20 +/- 2.7 mg/kg), respectively. The water-soluble, NH4Ac-extractable and HCl-extractable F in soil profiles were significantly correlated (P < .01). F concentrations in all soil layers (n = 51) of soil profiles (n = 17) were significantly correlated (P < .01) to Al concentrations in terms of water-soluble Al/F, HCl-extractable Al/F and NH4Ac-extractable Al/F, due to the formation of Al-F complexes in soil. F contents extracted with deionized water (pH = 6.68), 1 mol/l HCl and 1 mol/l NH4Ac in soil could be used to predict F concentrations in the leaves, stems and roots of the six plants.     

水田土壤中水溶性有机物的产生动态及对土壤中重金属活性的影响:田间微区试验

采用田间微区试验研究不同施肥处理对土壤水溶性有机物 (DOM)的动态变化及其对土壤Cd活性的影响 结果表明 ,与施化肥对照处理相比 ,施用有机肥后土壤中DOM含量明显增加 .但随着水稻的生长DOM呈不断下降的趋势 ,而对照处理的变幅不大 ;在水稻整个生长过程中根际DOM含量不断增加且都高于对应时期土壤DOM的含量 ,并至水稻扬花期最大 ,此时 ,3种处理的根际产生DOM浓度 (DOM浓度以水溶性有机碳 (DOC)计 ,以下同 )分别为 :绿肥与化肥配施处理组 (GM) ( 14 0 2mg·L-1) >猪粪与化肥配施处理组 (PM) ( 11 12mg·L-1) >对照处理组 (F) ( 10 8mg·L-1) .水稻扬花期后 ,各处理的DOM含量不断下降 .试验还指出 ,有机肥施用后根际及土体土壤中交换态及有机结合态Cd含量显著增加 ,是对照处理的 2倍之多 ,同时发现 ,水稻收获后土壤交换态Cd的含量与此时的土壤DOM含量呈明显的正相关 (r土体 =0 92 6 6 ,n =8;r根际 =0 9389 ,n =8) .施用有机肥改良重金属污染土壤应该谨慎