Elaboration of the hydroxyapatite with different precursors and application for the retention of the lead

Carbonate hydroxyapatite (CHAP) was synthesized from different precursors; synthetic (CaCO3 and Ca(OH)2) and natural (egg shell before and after calcinations at 900 degrees C) under different conditions and characterized by using TG/DTG analysis, X-ray powder diffraction (XRD) method and Fourier transform infrared (FT-IR) spectroscopy techniques. The results of these analyses indicate that the four powders present the same structure of hydroxyapatite. Furthermore the four powders obtained were used for the retention of lead. The results obtained indicated that all powders present high adsorption capacity for lead, but from environmental and economic views, the hydroxyapatite synthesized from eggshell no calcined (HA2) is most advantageous. The influence of different sorption parameters, such as: initial metal concentration, equilibration time, solution pH and sorbent dosage was studied and discussed.     

Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.     

The fate of 14C-radiolabelled diclofenac and 4'-hydroxydiclofenac in membrane bioreactor treatment of wastewater

This study aimed at enhancing knowledge on the fate of diclofenac (DF), together with its main human metabolite 4'-hydroxydiclofenac (4'OHDF), during wastewater treatment by using a laboratory-scale membrane bioreactor (MBR). The reactor was fed continuously with non-radiolabelled diclofenac for a one month period prior to a single pulse of a 14C-radiolabelled solution of DF and 4'OHDF. The solution spike contained approximately 25% 4'OHDF and 65% DF, which corresponds to the ratio observed in municipal sewage, as well as traces of two other metabolites. The radioactivity was monitored for a total of twelve days in the various output streams. The calculation of the complete mass balance in the system demonstrated that the major part of the radioactivity left the reactor with the permeate (88.7%), while 2.1% was recovered in the excess sludge. Negligible amounts were recovered in the off-gas traps and on the membranes. Chromatographic analyses of effluent samples, by means of HPLC-MS coupled in parallel to a radiodetector, displayed a different pattern than the one of the spiked solution. It showed the occurrence of three additional metabolites.     

Constructed wetland as a low cost and sustainable solution for wastewater treatment adapted to rural settlements: the Chorfech wastewater treatment pilot plant

The paper presents the detailed design and some preliminary results obtained from a study regarding a wastewater treatment pilot plant (WWTPP), serving as a multistage constructed wetland (CW) located at the rural settlement of 'Chorfech 24' (Tunisia). The WWTPP implemented at Chorfech 24 is mainly designed as a demonstration of sustainable water management solutions (low-cost wastewater treatment), in order to prove the efficiency of these solutions working under real Tunisian conditions and ultimately allow the further spreading of the demonstrated techniques. The pilot activity also aims to help gain experience with the implemented techniques and to improve them when necessary to be recommended for wide application in rural settlements in Tunisia and similar situations worldwide. The selected WWTPP at Chorfech 24 (rural settlement of 50 houses counting 350 inhabitants) consists of one Imhoff tank for pre-treatment, and three stages in series: as first stage a horizontal subsurface flow CW system, as second stage a subsurface vertical flow CW system, and a third horizontal flow CW. The sludge of the Imhoff tank is treated in a sludge composting bed. The performances of the different components as well as the whole treatment system were presented based on 3 months monitoring. The results shown in this paper are related to carbon, nitrogen and phosphorus removal as well as to reduction of micro-organisms. The mean overall removal rates of the Chorfech WWTPP during the monitored period have been, respectively, equal to 97% for total suspended solids and biochemical oxygen demand (BOD5), 95% for chemical oxygen demand, 71% for total nitrogen and 82% for P-PO4. The removal of E. coli by the whole system is 2.5 log units.     

Dynamic changes of the ecological environment quality in a river basin: a case study of the main stream of Songhua river basin

This paper reports the investigation and analysis of the status and dynamic changes of ecological environment quality in the main stream of Songhua river basin. The evaluation index system was established and the eco-environment quality in the year of 2000 and 2008 was studied in depth. Based on our research, the trend of dynamic changes of the eco-environment quality and its origins have been further discussed: In the year of 2000, the range of evaluation index covered from 0.31 to 0.47. Harbin and Yichun was relatively better than the rest of study areas. In the year of 2008, except districts of Daqing and Qitaihe, the environmental quality of Songhua river basin has entirely improved, wherein the evaluation index of the eco-environment covered from 0.31 to 0.57. Particularly, the eco-environment quality of Hegang and Shuangyashan has obtained significant improvement, whereas the improvement of Jiamusi was not obvious. According to the evaluation results, the environmental quality in the study area has an upward trend with the average growth rate 0.13% per year.     

Urine nitrification and sewer discharge to realize in-sewer denitrification to simplify sewage treatment in Hong Kong

The chemically enhanced primary treatment works in Hong Kong will be upgraded for biological nitrogen removal. This study proposed a novel approach to waive the upgrading by urine source-separation, onsite nitrification and discharge of nitrified urine into sewers to achieve in-sewer denitrification. Human urine was collected and a lab-scale experiment for full urine nitrification was conducted. The results showed that full nitrification was achieved with alkaline addition. Simulation of nitrified urine discharge into an 8-km pressure main in Hong Kong was conducted with a quasi-2D dynamic sewer model developed from a previously calibrated sewer biofilm model. It was assumed that 70% of the residents' urine was collected and fully nitrified on-site. The simulation results revealed that the proposed approach is effective in removal of nitrogen within the sewer, which decreases ammonia-N at the sewer outlet to a level required for secondary effluent discharge in Hong Kong.     

脱水导致的某些特殊疼痛

医学上的很多疾病都是我们无意识地进入脱水状态所致,因为身体最终会把缺水这一局面,通过某种奇特而确凿的方式显示出来。例如我们已谈过的胃灼热、胃痛等。以下疼痛也与缺水有关。     

脱水 让身体面临危机

关节脱水的后果如果关节脱水,软骨细胞就会处于强烈的摩擦状态,从而使它们迅速死亡,而死亡的细胞需要得到替换。软骨使用过度,并且处在修复状态,它就可能受到损伤,这一区域的感应器就会发出强烈的信号,表达它们急需修理的愿望。     

水管理决策对城市生存的影响(下)——从古代特诺奇提特兰城到现代墨西哥城

水管理决策影响城市的可持续发展.基于这些决策所开展的行动可缓解、甚至预防某些与水有关的风险.同样,这些决策也可能加大已存在的危险或产生新的危险.决策机构解决水问题的能力、对应优先解决水问题的理解,都会影响水管理决策.自墨西哥城建立以来,居民就一直面临供水不足、水质低下、卫生设施缺乏、洪涝频发等问题.为改善该市水管理现状,借鉴以往成功经验和失败教训,分析了几个世纪以来水管理政策的变化情况,并阐述了其对城市居民和环境的影响.以墨西哥城水管理决策和措施的演变为例,论述了这些水管理决策的可持续性,并指出了未来水政策的关键方向.