Impact assessment of odours emitted by a wastewater treatment plant

Complaints from the Domingos Martins population about sewage odours in the city made the district attorney order an impact assessment of the odours emitted by the city wastewater treatment plant (WWTP). This study comprised various techniques, models and population surveys. In 2007, an odour emission model proved that the main hydrogen sulphide emitter was the aeration tank of the WWTP (13.5 g h(-1)) and such emissions, according to CALPUFF model, should be perceived in the whole Domingos Martins city centre area. In this area, 58% of those interviewed were annoyed by the WWTP odours. However, in 2009, the odour monitoring panel recorded few odour occurrences. A second population survey showed that hereafter only 20% of those interviewed were annoyed by the WWTP emissions. Odour emission and dispersion models run with 2010 data proved a drastic reduction of the WWTP aeration tank emissions and consequently the city centre was not bothered by WWTP emissions anymore. The odour emission reduction was due to the modification of the WWTP aeration tank system. Despite the odour emission reduction, houses located southeast of the WWTP were still annoyed by sewage odours. However, in this part of the town, other sources of sewage odours have been found.     

Anaerobic monodigestion of poultry manure: determination of operational parameters for CSTR

In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.     

Ammonia oxidizing bacterial community composition and process performance in wastewater treatment plants under low temperature conditions

Nitrification can be difficult to maintain at wastewater treatment plants (WWTPs) during cold periods resulting in disrupted nitrogen removal. The aim of this study was to relate nitrification process performance to abundance and composition of the ammonia oxidizer communities in two closely located municipal WWTPs in Sweden during an eight month period covering seasonal changes and low temperature conditions. Both facilities showed lower NH(4)(+)-N removal efficiency and nitrification rates as temperature decreased. However, one of the plants had a more stable nitrification rate and higher ammonia removal efficiency throughout the entire period. The differences in performance was related to a shift in the composition of the bacterial ammonia oxidizing community from a Nitrosomonas oligotropha-dominated community to a mixed community including also Nitrosomonas ureae-like ammonia oxidizers. This was likely a response to differences in NH(4)(+)-N and organic loading.     

Evaluation and thermodynamic calculation of ureolytic magnesium ammonium phosphate precipitation from UASB effluent at pilot scale

The removal of phosphate as magnesium ammonium phosphate (MAP, struvite) has gained a lot of attention. A novel approach using ureolytic MAP crystallization (pH increase by means of bacterial ureases) has been tested on the anaerobic effluent of a potato processing company in a pilot plant and compared with NuReSys(?) technology (pH increase by means of NaOH). The pilot plant showed a high phosphate removal efficiency of 83 ± 7%, resulting in a final effluent concentration of 13 ± 7 mg · L(-1) PO(4)-P. Calculating the evolution of the saturation index (SI) as a function of the remaining concentrations of Mg(2+), PO(4)-P and NH(4)(+) during precipitation in a batch reactor, resulted in a good estimation of the effluent PO(4)-P concentration of the pilot plant, operating under continuous mode. X-ray diffraction (XRD) analyses confirmed the presence of struvite in the small single crystals observed during experiments. The operational cost for the ureolytic MAP crystallization treating high phosphate concentrations (e.g. 100 mg · L(-1) PO(4)-P) was calculated as 3.9 € kg(-1) P(removed). This work shows that the ureolytic MAP crystallization, in combination with an autotrophic nitrogen removal process, is competitive with the NuReSys(?) technology in terms of operational cost and removal efficiency but further research is necessary to obtain larger crystals.     

Protein analysis as a measure of active biomass in activated sludge

Conventional methods to determine the biomass in activated sludge are the measurement of total suspended solids (TSS) and volatile suspended solids (VSS). Such methods do not distinguish between active biomass and inactive organic material. In this study, biomass was determined with both conventional methods and also through measuring the protein content with the modified Lowry method. In order to investigate the relationship between activity and biomass concentration in terms of TSS, VSS and protein content, some starvation experiments were conducted. It was found that the protein fraction of VSS differs under different starvation conditions. The biological activity of the activated sludge was measured as oxygen uptake rate (OUR). The strongest correlation could be measured between protein and OUR under various conditions. The results show that protein is an appropriate parameter for the measurement of the biological activity.     

A novel combined electrochemical-magnetic method for water treatment

Electrocoagulation (EC) is a wastewater treatment process in which aqueous pollutants can be removed by adsorption, entrapment, precipitation or coalescence during a coagulation step produced by electrochemically generated metallic species. When using Fe as the sacrificial electrode, Fe(2+) and Fe(3+) ions are formed. As Fe(3+) species are paramagnetic, this property can in principle be used to facilitate their removal through the application of a magnetic field. In the present work we present a proof-of-concept for a combined electrochemical-magnetic method for pollutant removal. For this approach, the amounts of Fe(2+) and Fe(3+) produced in an EC cell at various voltages were measured by spectroscopic methods to confirm that Fe(3+) species predominate (up to 84%). The effectiveness of the presence of a magnetic field in the precipitation of coagulants from a suspension was confirmed by monitoring the turbidity change versus time with and without exposure to a magnetic field, up to a 30% improvement.     

论金融控股公司的监管

对金融机构直接施加业务限制，目的是为了保障受管制公司的偿付能力，确保公众权利人的利益和保护金融机构免受其他金融机构倒闭的负面外部效应的影响。     

银行业监管架构与银行业绩效

本文是《银行家》杂志美国特约编辑James Barth博士的荐稿。丹尼尔E.诺勒(Daniel E.Nolle)先生是美国货币监理署(United States Office of the Comptroller of the Currency)的高级金融经济学家。在对世界上100多个国家的银行业监管构架进行调查的基础上,作者认为,银行业的监管架构实际上对银行业的绩效影响非常有限。关于如何构建银行监管体系这种政策性的辩论,可能要集中在监管结构对银行体系其他方面的影响,这些方面包括单个银行的安全性和稳健性,整个银行体系的稳定性以及未来发展等等。     

全球化：前景、潜力与问题

本文扼要阐述了经济全球化发展的前景和潜力,并运用李嘉图模型对全球化可能导致的经济损害作出论证分析进而说明,尽管经济学家在极大程度上趋向于将全球化视为基本良性的现象,但全球化仍然对某些国家（包括发达国家）带来经济损害,及对部分人群可能造成极其痛苦的后果。不过,源自于全球化的不断增长的竞争压力,会加强创新和增长,从长远来看,的确对每个国家有利。     

美国控制温室气体排放的市场化政策选择

在历史上,美国习惯于采用指挥与控制法来减少污染物排放。然而,这种规制措施会降低产业部门的生产效率。文章引入基于市场机制的两种碳价政策,一是碳税,二是总量控制与交易计划,并对这两种政策选择的设计进行了探讨,对二者在不确定性条件下的减排效果、促进政府税收、加强行政管理等方面的差异进行了比较,认为采用一种将碳税和总量控制与交易计划结合在一起的综合性碳价政策,在效率和分配方面要优于指挥与控制法。