Development of low-cost technology for the removal of iron and manganese from ground water in siwa oasis

Background: Ground water is the only water resource for Siwa Oasis. It is obtained from natural freshwater wells and springs fed by the Nubian aquifer. Water samples collected from Siwa Oasis had relatively higher iron (Fe) and manganese (Mn) than the permissible limits specified in WHO Guidelines and Egyptian Standards for drinking water quality. Aeration followed by sand filtration is the most commonly used method for the removal of iron from ground water. Aim: The study aimed at development of low-cost technology for the removal of iron and manganese from ground water in Siwa Oasis. Material and Methods: The study was carried out on Laboratory-scale columns experiments sand filters with variable depths of 15, 30, 45, 60, 75, 90 cm and three graded types of sand were studied. Results: The graded sand (E.S. =0.205 mm, U.C. =3.366, depth of sand = 60 cm and filtration rate = 1.44 m3/m2/hr) was the best type of filter media. Iron and manganese concentrations measured in ground water with aeration only, decreased with an average removal percentage of 16%, 13% respectively. Iron and manganese concentrations after filtration with aeration came down to 0.1123, 0.05 mg/L respectively in all cases from an initial concentration of 1.14, 0.34 mg/L respectively. Conclusion and Recommendations: Advantages of such treatment unit included simplicity, low cost design, and no need for chemical addition. In addition, the only maintenance required was periodic washing of the sand filter or replacement of the sand in order to maintain reasonable flow rate through the system.     

强化饮水除砷剂的研制

长期饮用高砷水有害人体健康 ,而改饮低砷水可以缓解已发病者的症状。研究经济、高效、简便的饮水除砷剂是十分必要的。本课题研制的强化除砷剂具有除砷容量高 ,出水的含砷量低于 0 0 5mg L ;除砷功能专一 ,即只除去水中的砷而不改变水中其它元素的组成和含量 ;操作管理简单 ,进水、出水均无需调节pH ;除砷成本低 ,每吨成本仅为活性氧化铝或颗粒活性炭的 1 5 ,氧化催化剂可重复使用。有望广泛用于高砷水地区集中式和分散式供水的除砷系统。     

分散式饮水中三价砷的去除

在利用硫酸铁去除五价砷 [As(V) ]的基础上研究了三价砷 [As(III) ]的氧化及去除 ,以寻求适合于分散式饮水中 As(III)的氧化方法。结果显示 :水中 As(III)的自然氧化过程相当缓慢 ,曝气 2 4h亦难以加速其氧化 ;通入臭氧 6 0 s,或按 7.5 m l/ L 投加双氧水 ,按投氯量加 2 .5 m g/ L 次氯酸钠或 15 m g/ L 的漂白粉等 ,均可有效氧化 1.0 m g/ L As(III) ,使砷去除率近似于 As(V)的去除率 ;选取次氯酸钠作为氧化剂 ,进一步研究发现其氧化效果不受水质 p H值、硬度、As(III)初浓度、As(III) / As(V)的配比等的影响 ,而且 1.2 5 m g/L 投加量可有效氧化≤ 0 .8mg/ L 的 As(III) ,现场实验亦证实了其氧化效果。本研究结果表明 ,次氯酸钠是一种效果可靠、经济技术可行的分散式饮水三价砷的氧化剂。     

Evaluation of activated carbon filters for removal of ozone at the PPB level.

Performance of filters for the removal of ozone at ambient concentration is characterized. The removal efficiency and pressure drop of 10 commercial filters--including 8 made of granule or powdered activated carbon, 1 activated carbon fiber filter, and 1 packed bed made of an ozone catalyst--were measured for an influent ozone concentration of 120 ppb at 50% relative humidity and 2.54 m/sec face velocity. Activated carbon filters can be very effective at ozone removal, although not indefinitely because chemical reactions of ozone and carbon change the carbon. Initial efficiencies of the 1.27-cm thick flat samples varied from 4.6 to 98.3%. Analysis of the structure and composition of the filters with scanning electron microscopy and X-ray photoemission spectrometry showed chemical reactions permanently changed the composition of the carbon and decreased the surface area. Consequently, removal efficiency decreased with use. Moreover, it was not feasible to regenerate the filters by simply removing them from ozone-laden air. Changes in relative humidity, from 20 to 80%, had no measurable effect on the performance of a granule activated carbon filter. However, because the rate of adsorption of water is faster and the pores are smaller in activated carbon fiber, efficiency of the fiber filter decreased when relative humidity was raised from 20 to 50%. A quality factor, equal to the ratio of a threshold breakthrough time and pressure drop, is used to compare filters. In general, those with higher carbon surface area per unit volume had higher efficiencies and greater pressure drops. Future work should address the removal of ozone in the presence of other gases.     

Removal of airborne bacteria by filtration using a composite microporous membrane made of a pyridinium-type polymer showing strong affinity with microbial cells.

A composite microporous membrane made of poly(N-benzyl-4-vinylpyridinium chloride) that showed strong affinity with bacterial cells was prepared as a filter material for removing airborne bacteria. Thickness, pore diameter and porosity of the membrane were 0.72 mm, 14.5 microm and 63%, respectively. Electron micrographic analysis revealed that the membrane consisted of a very large number of connected beads of 1.4 microm in diameter made of the pyridinium-type polymer. Filtration using the membrane was performed easily at low flow rates with insignificant pressure drop across the membrane. Filtration at 63.7 cm/sec gave 99.98% and 99.996% removal (3.7 and 4.4 log10-unit reduction in concentration) of Escherichia coli and Pseudomonas aeruginosa, respectively. Staphylococcus aureus was not detected in filtrates. Since pores of the membrane were much larger than these bacteria, the efficient removal was best explained in terms of the affinity of the polymer with bacterial cells.     

上海市供水系统微囊藻毒素LR含量调查

目的　调查上海市供水系统中微囊藻毒素LR(MC- LR)的污染状况及常规水处理工艺对MC- LR的去除效果。方法　运用高效液相色谱法 (HPLC)检测有代表性的水源、水厂及出厂水样中MC LR的含量。结果　源水中MC- LR浓度随采样点及采样季节变化 ,在夏末秋初易形成污染高峰 ,最高达 2 . 38μg L。混凝沉淀、加氯消毒对去除毒素有一定的效果 ,而过滤则效果不明显 ,在出厂水中也能检测到MC- LR ,最高达1. 2 7μg L。结论　夏秋季节上海市供水系统源水受到以MC- LR为代表的蓝藻毒素的污染 ,郊区源水污染较重 ,常规水处理工艺不能有效地去除水中的微囊藻毒素。     

催化-臭氧在游泳池水质处理的应用

目的:建立一种用催化-臭氧方法氧化游泳池水中尿素,以使得游泳池水中的尿素、细菌总数、大肠菌群指标符合国家标准。方法:用不同的方法,如改性沸石过滤试验;加氯试验;臭氧氧化试验;臭氧加入催化剂(催化剂为硫酸铜或五氧化二矾)等试验观察尿素的去除效果。结果:催化-臭氧方法去除尿素效果最好,臭氧加入以硫酸铜为催化剂的催化方法尿素去除率为76.3%,臭氧加入以五氧化二矾为催化剂的催化方法尿素去除率为76.8%,高浓度氯(有效氯含量5.0 mg/L)消毒剂效果次之,去除率为46.1%。结论:理想的去除游泳池水尿素及杀灭细菌的有效方法为臭氧发生器连接游泳池本身的循环水处理系统。     

石化工业废水深度处理工艺各单元处理效果研究

目的研究某石化公司工业废水深度处理工艺效果,以减少环境污染、降低用水成本、提高水资源利用率,对该工艺的应用推广具有重要意义。方法采用的"絮凝气浮+BAF(曝气生物滤池)+多介质过滤+臭氧接触氧化+生物活性炭过滤+超滤反渗透双膜"工艺进行废水处理,利用紫外分光光度法、微波消解法、重量法、纳氏比色法等监测分析方法对各项污染物进行监测分析。结果絮凝气浮、BAF、多介质过滤单元对悬浮物去除较好,去除率为89.9%;臭氧化单元对石油类去除较好,去除率为62.5%,对氨氮反而增加,其浓度增加6.0%;生物活性炭去除氨氮及悬浮物较好,氨氮去除率达到79.1%,悬浮物去除率为98.3%;超滤反渗透单元去除氨氮较好,去除率为46.1%。数据显示生物活性炭单元出水已达到设计标准。结论各处理单元污染物监测指标显示,该石化公司采用的工业废水深度处理工艺流程的3个单元整体性能良好,处理后出水达到了设计要求。     

A study of the efficacy of various home filtration substrates in the removal of microcystin-LR from drinking water

This study was conducted to determine whether common water filtration and purification systems bought by consumers and used in the home would remove cyanotoxins from water. Commonly used universal filter housings and filter sizes were utilized to identify filter media that may be effective in the removal of microcystin-LR in deionized water. Results suggest that the efficacy of home filtration devices in removing microcystin-LR varies considerably with the type of device being used. Carbon filters successfully removed microcystin-LR allowing only 0.05-0.3% of the toxin load to pass through the filter. On the other hand, pleated paper and string wound filters allowed > 90% of microcystin-LR present in the sample to pass through the filters. Theoretically, the use of carbon home filtration devices tested in this study may provide protection against human exposure to cyanotoxin in addition to protection provided by water treatment methodologies utilized in water treatment facilities. Further studies need to be done to assess the efficacy of home filtration devices for various cyanotoxins and for other filtering conditions such as increased toxin load, the presence of other contaminants in drinking water, and the repetitive use of the same filter over longer time intervals.     

Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries

Over 1.1 billion people in the world lack access to improved drinking water. Diarrhoeal and other waterborne diseases cause an estimated 1.9 million deaths per year. The Safe Water System (SWS) is a proven household water treatment intervention that reduces diarrhoeal disease incidence among users in developing countries. Turbid waters pose a particular challenge to implementation of SWS programmes; although research shows that a 3.75 mg l^-1 sodium hypochlorite dose effectively treats turbid waters, users sometimes object to the strong chlorine taste and prefer to drink water that is more aesthetically pleasing. This study investigated the efficacy of three locally available water clarification mechanisms—cloth filtration, settling/decanting and sand filtration—to reduce turbidity and chlorine demand at turbidities of 10, 30, 70, 100 and 300 NTU. All three mechanisms reduced turbidity (cloth filtration -1–60%, settling/decanting 78–88% and sand filtration 57–99%). Sand filtration (P=0.002) and settling/decanting (P=0.004), but not cloth filtration (P=0.30), were effective at reducing chlorine demand compared with controls. Recommendations for implementing organizations based on these results are discussed.     

Occupational dimethylformamide exposure

A diffusive sampling method with water as absorbent was examined in comparison with 3 conventional methods of diffusive sampling with carbon cloth as absorbent, pumping through National Institute of Occupational Safety and Health (NIOSH) charcoal tubes, and pumping through NIOSH silica gel tubes to measure time-weighted average concentration of dimethylformamide (DMF). DMF vapors of constant concentrations at 3-110 ppm were generated by bubbling air at constant velocities through liquid DMF followed by dilution with fresh air. Both types of diffusive samplers could either absorb or adsorb DMF in proportion to time (0.25-8 h) and concentration (3-58 ppm), except that the DMF adsorbed was below the measurable amount when carbon cloth samplers were exposed at 3 ppm for less than 1 h. When both diffusive samplers were loaded with DMF and kept in fresh air, the DMF in water samplers stayed unchanged for at least for 12 h. The DMF in carbon cloth samplers showed a decay with a half-time of 14.3 h. When the carbon cloth was taken out immediately after termination of DMF exposure, wrapped in aluminum foil, and kept refrigerated, however, there was no measurable decrease in DMF for at least 3 weeks. When the air was drawn at 0.2 l/min, a breakthrough of the silica gel tube took place at about 4,000 ppm.min (as the lower 95% confidence limit), whereas charcoal tubes could tolerate even heavier exposures, suggesting that both tubes are fit to measure the 8-h time-weighted average of DMF at 10 ppm.     

Fate and effects of triclosan in activated sludge

Triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol) is a widely used antimicrobial agent. To understand its fate during sewage treatment, the biodegradation and removal of TCS were determined in activated sludge. In addition, the effects of TCS on treatment processes were assessed. Fate was determined by examining the biodegradation and removal of TCS radiolabeled with 14C in the 2,4-dichlorphenoxy ring in laboratory batch mineralization experiments and bench-top continuous activated-sludge (CAS) systems. In batch experiments with unacclimated sludge, TCS was mineralized to 14CO2, but the total yield varied as a function of test concentration. Systems that were redosed with TCS exhibited more extensive and faster mineralization, indicating that adaptation was a critical factor determining the rate and extent of biodegradation. In a CAS study in which the influent level of TCS was incrementally increased from 40 microg/L to 2,000 microg/L, removal of the parent compound exceeded 98.5% and removal of total radioactivity (parent and metabolites) exceeded 85%. Between 1.5 and 4.5% of TCS in the influent was sorbed to the wasted solids, whereas >94% underwent primary biodegradation and 81 to 92% was mineralized to CO2 or incorporated in biomass. Increasing levels of TCS in the influent had no major adverse effects on any wastewater treatment process, including chemical oxygen demand, biological oxygen demand, and ammonia removal. In a subsequent experiment, a CAS system, acclimated to TCS at 35 microg/L, received two separate 4-h shock loads of 750 microg/L TCS. Neither removal of TCS nor treatment processes exhibited major adverse effects. An additional CAS study was conducted to examine the removal of a low level (10 microg/L) of TCS. Removal of parent equaled 94.7%, and biodegradation remained the dominant removal mechanism. A subsequent series of CAS experiments examined removal at four influent concentrations (7.5, 11, 20, and 50 microg/L) of TCS and demonstrated that removal of parent ranged from 98.2 to 99.3% and was independent of concentration. Although TCS removal across all experiments appeared unrelated to influent concentration, removal was significantly correlated (r2 = 0.87) with chemical oxygen demand removal, indicating that TCS removal was related to overall treatment efficiency of specific CAS units. In conclusion, the experiments show that TCS is extensively biodegraded and removed in activated-sludge systems and is unlikely to upset sewage treatment processes at levels expected in household and manufacturing wastewaters.     

Removal of indicator microorganisms and enteroviruses from wastewater in a single cell stabilization pond

A study was performed to evaluate the removal efficiency of bacterial indicators, F⁺bacteriophages and enteroviruses, in a single‐cell stabilization pond with a design hydraulic detention time of six to ten days. The performance of the stabilization pond was also evacuated by measuring the pH, conductivity and the level of dissolved oxygen in the influent and effluent. A dye tracer study indicated that 5% of the pond influent reached the pond's outlet within 16 h, indicating severe short‐circuiting in the pond. The removal of the indicator microorganisms ranged between 90.7 to 96.6% in the stabilization pond. Average concentration of F. coliform, enterococci and F⁺bacteriophage in the pond's effluent was 2.1 X 10⁴, 1.2 X 10² and 1.6 X 10² cfu or pfu/ml^‐1, respectively. The microbial quality of the effluents obtained does not meet the WHO recommended guidelines for effluents reuse for unrestricted crop irrigation. Uncontrolled discharge of these low quality effluents may result in the contamination of natural water resources.     

Arsenic Remediation from Drinking Water Using Fenton’s Reagent with Slow Sand Filter

This paper describes the development of a remediation approach based on the pre-oxidation using Fenton’s reagent and the subsequent removal of arsenic (As) through sand filtration from drinking water. The efficiency of the process was carried out including As(III) and As(V) with various concentration ratios up to 3,000 ppb. Efficient removal of As was observed within WHO guideline value of 10 ppb. The recoveries of samples were found to be 98 % ± 2.5 %. The process was applied to field samples, where results show considerable reduction in As concentrations. This process is cost effective for treatment of drinking water with high concentration of As.     

Review of coagulation technology for removal of arsenic: case of Chile

Coagulation technology has been used since 1970 in northern Chile for removing arsenic from drinking-water. This experience suggests that coagulation is an effective technology for the removal of arsenic. It is currently possible to reduce arsenic from 400 microg/L to 10 microg/L at a rate of 500 L/sec, assuming pH, oxidizing and coagulation agents are strictly controlled. The Chilean experience with the removal of arsenic demonstrates that the water matrix dictates the selection of the arsenic-removal process. This paper presents a summary of the process, concepts, and operational considerations for the use of coagulation technology for removal of arsenic in Chile.     

Biological treatment of wastewater from the cassava meal industry

Biological treatments of cassava meal processing wastewaters were investigated by aerobic and combined anaerobic/aerobic reactors. As a pretreatment, flocculation and sedimentation with aluminum salts and natural polyelectrolytes were employed, in order to change the effluent concentration of organics from 14,000 to 2000 mg/L in the bench scale reactor, with a hydraulic retention time of 37 min and an influent rate of 0.56 L/cm. Biological degradation by an activated sludge process was carried out using a reactor volume of 20 L. The observed organic matter removal rates were 89 to 93%, the cyanide removal was 95 to 99%, and the food to microorganisms ratio was found to be in the range of 0.166 to 0.242/day, with a hydraulic residence time of 1.4 to 4.2 days. As a posttreatment, flocculation and coagulation were employed, resulting in an effluent of good quality, as shown by turbidity measurements and negative tests for fecal and total coliforms.     

一次性角膜标本采集器的研制

目的:研制一种一次性角膜标本采集器。方法:根据传统角膜标本采集方法与要求进行设计,采集器包含手柄、颈部和头部3部分。结果:整体设计简单新颖,质量小,易操作,能够一次安全采集足量检验标本。结论:一次性角膜标本采集器制作成本低,使用安全,操作简单,取样检出率高,值得推广、使用。     

Removal of viruses from sewage, effluents and waters. 2. Present and future trends

Because large variations occur in the concentrations of viruses that enter treatment plants from season to season and from place to place, and even during a 24-hour period, field studies on the removal of viruses by treatment processes require temporal coordination of sampling. Quantitative methods for concentrating viruses must be developed to measure accurately the efficiency of virus removal by treatment processes in field situations. Extended settling, and storage of sewage and raw waters, reduce virus levels and deserve further study. Oxidation ponds must be reevaluated with regard to temporal matching of influent and effluent samples and with special care to prevent short-circuiting. Conventional and modified activated sludge plants must be reassessed with temporal matching of samples. Coagulation of viruses with metal ions requires field evaluation, and virus removal by filtration through sand and other media, under constant salt and organic loadings, needs both laboratory and field evaluation. A comparative study of water disinfectants related to specific conditions is needed. The toxicity, carcinogenicity, and teratogenicity of products resulting from disinfection must also be assessed. Other matters for investigation are: methods for quantitatively detecting viruses adsorbed on solids, the virus-removal capability of soils, better virus indicators, virus concentration in shellfish, the frequency of infection in man brought about by swallowing small numbers of viruses in water, the epidemiology of virus infection in man by the water route, the effect of viruses of nonhuman origin on man, and the occurrence of tumour-inducing agents in water.     

Establishment of minimum operational parameters for a high-volume static chamber steam pasteurization system (SPS 400-SC) for beef carcasses to support HACCP programs

A static chamber steam pasteurization unit (SPS 400-SC()) was installed in a high-volume commercial beef slaughter facility. The SPS 400-SC consists of a three-phase carcass treatment cycle of water removal, steam pasteurization, and water chilling. Seven chamber temperatures (71.1, 73.9, 76.7, 79.4, 82.2, 85.0, and 87.8 degrees C) were evaluated at the midline area of pre-rigor beef carcasses. For each temperature evaluated, 20 carcass sides were randomly selected and aseptically sampled by tissue excision immediately before and after steam pasteurization to determine total aerobic bacteria, Enterobacteriaceae, generic E. coli, and total coliform populations. The 87.8 and 85.0 degrees C treatment temperatures were highly effective at reducing total aerobic bacterial populations, with log(10) reductions of 1.4 and 1.5 CFU/cm(2), respectively, from pretreatment mean population levels of 1.7 and 1.9 log10 CFU/cm(2). These temperatures also reduced Enterobacteriaceae, total coliforms, and generic E. coli to undetectable levels (<0.4 CFU/cm(2)) on all carcasses sampled. Treatment at 82.2 was marginally effective at reducing bacterial populations, while 71.1, 73.9, 76.7, and 79.4 degrees C treatments were ineffective at reducing microbial populations. In a Hazard Analysis Critical Control Points (HACCP)-based system employing steam pasteurization of carcasses as a critical control point, a critical limit of 85.0 degrees C as a minimum chamber temperature should be established, with a targeted operating temperature of 87.8 degrees C providing optimum antimicrobial activity.     

微波辐射对原代培养睾丸支持细胞的影响

目的 探讨微波辐射是否对原代培养睾丸支持细胞具有损伤效应.方法 建立原代培养睾丸支持细胞模型,经平均功率密度为30、100 mW/cm2微波辐射5 min,于辐射后6 h采用Annexin和V-PO双标、Fluo-3-AM荧光标记结合流式细胞术(FCM)和激光共聚焦显微镜(LSCM)检测支持细胞细胞周期、细胞凋亡坏死及胞内Ca2+含量的变化. 结果 30 mW/cm2微波辐射后6 h G0-G1和G2-M期细胞数明显减少(分别为62.57%±3.22%、8.25%±1.75%),S期细胞数明显增加(29.17%±4.87%),与对照组(分别为79.18%±0.24%、11.17%±0.50%、9.64%±0.62%)比较,差异有统汁学意义(P<0.05或P<0.01),但细胞凋亡和坏死率及胞内Ca2+含量无明显改变;而100 mW/cm2微波辐射后6 h G0-G1期支持细胞数明显增加(87.69%±1.32%),G2-M和S期细胞数明显减少(分别为7.41%±0.60%、4.87%±0.91%),与对照组的差异有统计学意义(P<0.01);胞内Ca2+含量及细胞凋亡坏死率明显增加,差异亦有统计学意义(P<0.05或P<0.01). 结论 100 mW/cm2微波辐射可引起培养支持细胞生长抑制及凋亡与坏死增加,胞内Ca2+升高是其损伤的重要机制.