Design guidelines for an optimum scrubber system

The revised New Source Performance Standards (NSPS) for the utility industry mandates reduced particulate matter and sulfur dioxide emissions from new utility boilers. A wet scrubber system can be an advantage in controlling both of these emissions. Existing wet scrubber systems may meet the new standards with significant increase in power consumption. A careful design of the entire scrubber system, based on the experience gained at the existing installations, is necessary to ensure cost effectiveness. The experience with existing wet scrubber systems used on coal-fired utility boilers is reviewed and their performance is correlated with power consumptions. Based on a correlation of scrubber pressure drop against outlet concentration, conventional scrubber systems would be able to meet the revised NSPS for particulate matter with a theoretical scrubber pressure drop of 43±5 cm H₂O. Overall system pressure drop, however, could easily run as high as 76 cm H₂O. Novel scrubber systems such as the electrostatically augmented scrubber may provide the necessary collection performance at lower pressure drops. The performance of the various scrubber components such as mist eliminators and reheaters is reviewed. Operating problems are also discussed.     

Evaluation of the Ceilcote ionizing wet scrubber

The Ceilcote ionizing wet scrubber installed on a refractory brick kiln was evaluated with tests involving particulate mass emission, particle size distribution, and opacity. The overall efficiency was 93% with an average outlet opacity of 8% on a 1.68 m (5.5 ft) path length. The average particle cut diameter of the scrubber is 0.5 microns with a theoretical power input of 67 W/am³ (2.5 hp/1000 acfm). The theoretical power requirement for the ionizing wet scrubber was 41 W/am³ (1.54 hp/1000 acfm). A cooling tower supplying chilled water to the prescrubber required an additional 26 W/am² (0.96 hp/1000 acfm) for a total system input of 67 W/am³ (2.5 hp/1000 acfm). It is recommended that the scrubber be considered where practical for the removal of fine particulate matter.     

Particulate removal and opacity using a wet venturi scrubber — the Minnesota Power and Light experience

Minnesota Power and Light is installing a wet venturi particulate scrubber and a spray tower SO₂ absorber as the Air Quality Control System for their 500 MW Unit #4, Clay Boswell Station, Cohasset, Minnesota. The system is being designed and installed by Peabody Process Systems, Inc., Stamford, Connecticut. Prior to start-up the full scale unit, a 1 MW pilot plant was installed and tested to evaluate the performance of the system. Extensive data was collected for two different western coals with regard to venturi particulate removal characteristics and its effect on opacity. Correlations were also developed using pilot plant opacity data to predict full scale opacity results. This paper summarizes the test results obtained and conclusions reached.     

复合构建湿地运行初期理化性质及氮的变化

研究了在间歇式进水条件下，复合构建湿地系统对氮的去除效果，阐述了湿度要、溶氧、pH等理化因子变化的原因。实验初期，系统尚处于不稳定时期，对N的去除不够理想。随着筚驼逐步步和稳定状态，对KN、NH4^ 、N、NO2^-有明显的去除效果，平均去除率分别为50％、66％和71％。硝化－反硝化作用是氨氮去除的主要途径。从总体上看，有植物系统中硝态氮的出水含量较对照系统同，说明间歇式进水以及植物的存在都有利于硝化作用的发生。实验发现，复合构建湿地在冬季仍能较好地改善水质，是一种有效的水链管理对策，对受污水体水质改善和水生态系统恢复具有重要意义。     

Analysis of priority pollutants at a primary aluminum production facility

This paper investigated the source of priority pollutants, assessment of the wastewater treatment plant, and priority pollutant removal efficiency for a single Soderberg-type primary aluminum plant.Forty-eight hour composite samples were collected from the following streams: (1) plant intake water; (2) wastewater from the primary air pollution control system (gas stream cooling water and wet ESPs); (3) secondary air pollution control system (room ventilation wet scrubber liquor); (4) paste plant briquette cooling water; and (5) final effluent after the wastewater treatment plant.Wastewater from the primary air pollution control system entered a conventional chemical coagulation (using slacked lime) — clarification plant. Clarified water from the clarifier was combined with the other three wastewater streams and flowed into a settling lagoon with a 20-h hydraulic retention time. Clarified lagoon water was finally discharged to the river.The principal source of organic compounds in the wastewater was from the primary and secondary air pollution control systems and results from the volatilization of petroleum coke and pitch in the Soderberg anode. Wastewater treatment plant removal efficiencies of greater than 85% were achieved for the majority of the organic priority pollutant species detected.     

Collection characteristics of a double stage scrubber to eliminate the paint mist from a spray booth

A 4.5 m³/min laboratory paint spray booth was built adopting a double-stage scrubber with heavy oil as the scrubbing liquid. The relationship between the collection efficiency E and the pressure drop ΔP was studied using a cylindrical paper tilter and a Digital Dust Counter. Experimental results indicated that the collection efficiency in this system is in accordance with the collection efficiency equation based on the theory of inertial impaction. With water used as the scrubbing liquid, the factor K is about 0.5 for single-stage scrubbing, while it is 0.6 for double-stage scrubbing. At a pressure drop of 60 mm of H₂O, heavy oil used as the scrubbing liquid gained about 2.0% more in collection efficiency than water. The zigzag baffler equipped for removing heavy oil mist was also effective for the paint mist collector, and 99.1% of E was gained at a pressure drop of 135 mm H₂O.     

复合垂直流人工湿地氧化还原特征及不同功能区净化作用研究

研究了复合垂直流人工湿地系统氧化还原电位（Eh）的时空变化规律及不同功能区中污染物的净化效果。结果表明：湿地系统下行流池表层、两池底层、上行流池表层Eh的变化范围分别为402～585、-87～-130、308～432 mV，沿水流方向依次形成了好氧A区/缺氧、厌氧区/好氧B区3个功能区。好氧A区是污染物去除的主要区域，BOD₅、COD_Cr、NH⁺_4- N的去除率分别为430%、484%、541%，特别是NH+4 N去除率占总去除率的79%；缺氧、厌氧区主要是进行反硝化反应和有机物的厌氧分解；好氧B区则主要是去除厌氧分解后的有机物以及进一步脱氮。另外，NH+4 N的去除率与系统各功能区Eh呈显著相关关系（〖WTBX〗p〖WTBZ〗＜001），而BOD₅、COD_Cr、NO^-_3-N的去除率与系统各功能区Eh相关性不显著。     

High velocity fabric filtration for control of coal-fired boilers

As a follow-up to a pilot study, a full scale investigation of applying high velocity fabric filtration to coal-fired boiler fly ash control was conducted. Two filter systems were separately applied to two 60,000 lb/h coal-fired boilers. Performance evaluations conducted over the course of a year included total mass removal efficiency and fractional efficiencies. One filtration system employed Teflon felt as the filter media while the second system employed Gore-Tex, a Polytetrofluorethylene (PTFE) laminate on PTFE woven backing. During the course of the year, a limited number of glass felt and woven glass bags were introduced into the house containing Gore-Tex. As a separate option, the second system was outfitted entirely with woven glass bags. Preliminary results indicate acceptable performance at air-to-cloth ratio of 6 to 1. Future plans call for utilizing one of the baghouse systems for SO₂ removal.     

Phosphate removal by activated carbon–silica nanoparticles composite,kaolin, and olive cake

This work aimed to utilize four low-cost materials, namely activated carbon (AC), activated carbon–nanoparticle composite, kaolin, and olive cake, for phosphate removal. Batch mode tests were used to evaluate the performance of the adsorbents. The parameters affecting the adsorption process such as pH, initial concentration, mixing time, dosage, and temperature were studied. The obtained results showed that the removal efficiency of the adsorbents followed the order of: activated carbon–nanosilica > activated carbon > kaolin > olive cake. The addition of silica nanoparticles significantly enhanced the removal efficiency of activated carbon by 18.1% reaching a removal efficiency of 98% at 15wt% nanosilica loading. The adsorption isotherm data fitted well with Langmuir and Redlich–Peterson models with a correlation coefficient of >0.98, which indicates a monolayer homogenous adsorption. The fitness of the kinetic models was ranked as: pseudo-second-order > pseudo-first-order > intraparticle model. The calculated values of ΔH° = 23.4 kJ/mole, ΔS° = 0.11 kJ/mole, and ΔG = ?7.4 to ?11.8 kJ/mole indicated the endothermic and spontaneous nature of adsorption. The positive value of activation energy (17.66 kJ/mole) and the very low value of the sticking probability (2.4 × 10^?4) suggest high indefinite sticking of the phosphate ions to the adsorbent surface. The removal efficiency increased with time, dosage, and temperature, while it decreased with the increase in the initial concentration at an optimum pH of 7. The obtained results buttressed the benefit of using silica nanoparticles to enhance activated carbon capacity for phosphate removal, while kaolin and olive cake provided lower removal.     

Risk management of viral infectious diseases in wastewater reclamation and reuse: Review

Inappropriate usage of reclaimed wastewater has caused outbreaks of viral infectious diseases worldwide. International and domestic guidelines for wastewater reuse stipulate that virus infection risks are to be regulated by the multiple-barrier system, in which a wastewater treatment process composed of sequential treatment units is designed based on the pre-determined virus removal efficiency of each unit. The objectives of this review were to calculate representative values of virus removal efficiency in wastewater treatment units based on published datasets, and to identify research topics that should be further addressed for improving implementation of the multiple-barrier system. The removal efficiencies of human noroviruses, rotaviruses and enteroviruses in membrane bioreactor (MBR) and conventional activated sludge (CAS) processes were obtained by a systematic review protocol and a meta-analysis approach. The log₁₀ reduction (LR) of norovirus GII and enterovirus in MBR were 3.35 (95% confidence interval: 2.39, 4.30) and 2.71 (1.52, 3.89), respectively. The LR values of rotavirus, norovirus GI and GII in CAS processes were 0.87 (0.20, 1.53), 1.48 (0.96, 2.00) and 1.35 (0.52, 2.18), respectively. The systematic review process eliminated a substantial number of articles about virus removal in wastewater treatment because of the lack of information required for the meta-analysis. It is recommended that future publications should explicitly describe their treatment of left-censored datasets. Indicators, surrogates and methodologies appropriate for validating virus removal performance during daily operation of wastewater reclamation systems also need to be identified.     

我国环境治理投资效率评价及其关键影响因素

在系统地归纳了环境治理投资效率的相关研究的基础上，依据构建评价指标体系的原则，以环境治理投资总额作为投入指标，以及环境治理投资在水、气、固体等方面控制绩效作为产出，建立我国环境治理投资效率的评价指标体系，构建基于DEA方法的我国环境治理投资效率评价模型，再以环境治理投资效率为母因素，以各评价指标为环境治理投资效率的影响因素，利用灰色关联度分析方法，构建我国环境治理投资效率的关键影响因素分析模型，通过《中国环境统计年鉴2010》和《中国统计年鉴2010》收集2009年我国各省市（自治区）投入产出数据，得到我国各省市的环境治理投资效率及其关键影响因素，证实控制关键因素--环境治理投资总额，能够有效地提高环境治理投资效率     

Energy and temperature performance analysis of geothermal (ground source) heat pumps integrated with permeable pavement systems for urban run-off reuse

Geothermal (ground source) heat pumps (GHP) and permeable pavement systems (PPS) have demonstrated their effectiveness in both industry and academic research during recent decades. To meet the rising demand for sustainable, recyclable and energy efficient techniques, research has focused on the combination of techniques to enhance existing or develop new applications.

This paper reports on an experimental programme that combined GHP with PPS for nutrient removal and system energy balancing. Experimental data collected over a 3-year period have provided evidence of highly efficient removal rates of up to 99% for ammonia–nitrate and biochemical oxygen demand; and 96% removal rates were obtained for orthophosphate–phosphorus. This paper also contains energy efficiency ratio (EER) and coefficient of performance (COP) calculations. Cyclic heat removal and heat rejection allowed for stable temperature and pump COP and EER sustainability. The results prove that PPS systems are appropriate for GHP installation, delivering high and stable pollutant removal with EER efficiencies between 1.5 and 5.5.

The combination of GHP with PPS has the potential to provide a new sustainable and eco-friendly practice.     

An evaluation of grid rod failure in a mobile bed scrubber

The body of information presented in this paper is directed to those engineers and maintenance personnel involved in the operation of mobile-bed scrubbers. Materials tests were performed on three specimens of austenitic stainless steel to determine the possible causes of grid rod failure in a mobile-bed scrubber controlling particulate emissions from a pulverized-coal-fired, steam-electric generating station. These three specimens were successively placed in an Instrom universal testing machine and loaded in tension until rupture occurred. The results of these tests, in addition to other supporting data, were used in an attempt to determine the cause of the grid rod failure during scrubber operation. It was determined that the grade of stainless steel used, the scrubber water quality, and certain operational problems could be causes of premature failure.     

中国城市土地供给制度绩效评价指标体系的建立及其应用研究

对一种制度的绩效进行量化评价是近年来制度经济学研究的热点问题之一。城市土地是城市形成与发展的基础，而土地资源的供给直接关系到城市的兴衰与区域的发展。近年来我国在城市土地供给制度上进行了较大的改革，作为一种制度改革，其绩效的评价具有一定的现实意义，可以实现评价的诊断功能和预瞀功能。本文通过对制度绩效评价分析，提出对制度绩效评价可以转化为对制度目标实现程度的评价，归纳出我国城市土地供给制度绩效的评价标准，遵循“效率优先。兼顾公平”的原则，以土地结构配置效应、经济效应和公平配置效应为表现，初步提出了现行的城市土地供给制度的绩效评价指标体系，并对南京市近年来的城市土地供给制度的绩效进行了实证研究，提出了相关建议。     

Application of slipstreamed air pollution control devices on waste-as-fuel processes

The recovery of energy from the combustion of municipal solid wastes is becoming an attractive alternative as landfill space becomes scarce and the availability of fossil fuels decreases. Particulate emissions from “waste-as-fuel” processes, however, may differ significantly in chemical and physical properties from particulate emissions produced by firing only coal. Such differences can affect the design and operation of air pollution control equipment. Presented in this paper are the results of a 2-month test program at Ames, Iowa, with a mobile electrostatic precipitator (ESP) and a mobile scrubber supplied by the U.S. Environmental Protection Agency (EPA), Industrial Environmental Research Laboratory (IERL), Research Triangle Park. PEDCo Environmental, Inc., and Acurex Corporation jointly conducted the test program to examine the effect of burning refuse-derived fuel (RDF) on particulate and heavy metal control efficiencies. The mobile ESP was used only as a primary control device, whereas the mobile scrubber was tested both upstream and downstream of the existing full-scale ESP. This paper also presents a status report on a PEDCo test program with a pilot fabric filter at Ames.     

Characterization of organics in aqueous effluents of coal conversion processes

High-resolution liquid chromatography is being applied to the characterization of refractory organic compounds present in coal conversion streams at concentrations as low as a few micrograms per liter. The chromatographic system, which was previously developed for the analysis of the molecular biochemical constituents in human body fluids, is capable of analyzing for compounds that are u.v.-absorbing and/or oxidizable with sulfatoceric acid. Aqueous samples from various coal-liquefaction experiments have been collected, concentrated when necessary, and chromatographed. The chromatographic fractions have then been subjected to a multiple-analytical identification procedure utilizing, in sequence, UV-spectrometry, gas chromatography, and mass spectrometry. With this procedure, 18 organics were identified and 15 were quantified in the effluent from the product scrubber of a bench-scale hydrocarbonization unit. In addition, numerous unknown constituents have been characterized with respect to gas chromatographic and mass spectrometric properties.     

Energy and exergy analysis of a PCM-based solar powered winter air conditioning using desiccant wheel during nocturnal

In this paper, heating and humidification of air for space have been carried out by using a phase change material (PCM)-based solar-powered desiccant wheel air conditioning (SPDWAC) in winter. The analysis of the setup has been done at different air flow rates. At low and high air flow rates, system has mean thermal coefficient of performance of 0.121 and 0.172, respectively, and mean exergy efficiency of 0.0787 and 0.0846, respectively. The mean thermal coefficient of performance of the system at high air flow rate (127.23 kg h-1) is 1.42 times the low air flow rate (63.62 kg h-1) and average exergy efficiency of the system at high air flow rate is 1.07 times the low air flow rate. It is observed that with an increase in air flow rate, efficiency of the evacuated tube solar air collector (ETSAC) increases. The average efficiency of the ETSAC at high air flow rate is 15.60%. The maximum average energy efficiency (17.80%) and exergy efficiency (17.08%) of the PCM storage system have been obtained at high air flow rate. The overall performance of the system showed that the use of PCM storage is feasible to run the system in winter during the hours of darkness.     

A Study on Theoretical Model and Applied Evaluation of Land Use Performance of High-tech Zone in Urban Fringe： A Case Study in Haidian District, Beijing

High-tech industrial zone is an important carrier for constructing innovative cities. It also plays an important role in implementing the national independent innovative strategy. However, most of the high-tech industrial zones have many problems in their development process, such as efficiency of land use, weakness of oriented function and lack of land intensive. To solve these problems, the authors of this paper introduced the concept of land use performance and established the theoretical model to assess the land use performance of high-tech industrial zones. The model consists of the following three-dimensional parts： land use benefit, land use efficiency and innovative function. Based on this theory model, an index system which was composed of three secondary indictors, eight tertiary indictors and 37 fourth-grade indictors was set up to evaluate the land use performance of high-tech zone. To avoid the defects of plus model and function model, the authors brought out a three-dimensional evaluation model to examine the index of the land use performance of the high-tech industrial parks, which equals to the evaluation indicator system of land use performance of high-tech zone based on the above research. The authors examined the land use performance of five different high-tech industrial parks in Haidian District, Beijing City. The results indicated that the indicator system performs better in the aspect of evaluating land use benefit, land use efficiency and function of the high-tech industrial zone compared with other models.     

Adsorption studies on coir pith for heavy metal removal

Biosorption efficiency of coir pith, a waste product from coir industry, was investigated in this study for the removal of metallic pollutants such as Ni, Cu and Zn from aqueous solutions. The disposal of coir pith is a major problem associated with the coir industries, especially working in the small-scale sector. The present study explores the effectiveness of utilization of coir pith, an accumulating waste, as a biosorbent for heavy metal removal. Batch mode studies were done to evaluate the efficiency of removal of metals under varying adsorption conditions of pH, metal concentration and contact time. Characterization studies of the biosorbent and SEM analysis were done. Kinetic modelling studies were tried using Lagergren pseudo-first-order and second-order models. Equilibrium studies were done using well-known Freundlich, Langmuir and D–R isotherm models. It was found that all isotherms are fitting well indicating the efficiency of coir pith as an adsorbent of heavy metals. The applicability of all the three isotherms to the sorption processes shows that both monolayer adsorption and heterogeneous energetic distribution of active sites on the surface of the adsorbent are possible. Due to the abundance and low cost of these materials, adsorption technologies developed can act as good sustainable options for the future in heavy metal removal from industrial effluents.     

Upgrading the conventional grease trap using a tube settler

Grease traps are widely used by most restaurants and food processing industries in Hong Kong to reduce oil and grease to an acceptable level before it can be discharged to public sewers. To meet demanding effluent standards in the future, it is necessary to polish the effluent by upgrading the conventional trap design. This study evaluated the possibility of upgrading traditional grease traps by installing tube settlers inside the trap. Their efficiency of removing chemical oxygen demand (COD) and oil/grease was examined to justify the performance. It was found that installing a tube settler is a feasible and cheap way to upgrade the conventional grease trap, since it improved oil/grease removal efficiency by 8-10% compared to the conventional design. In addition, a remarkable improvement in COD removal was observed following a very short hydraulic detention time after the installation of tube settlers. This ensured acceptable effluent quality under peak flowrates. Two mathematical models were also proposed to facilitate trap design.