Monitoring natural organic matter in surface water by UV spectroscopy : effects of calcium, magnesium and pH value

The aim of this study was to evaluate the effects of dissolved magnesium and calcium ions on the determination of humic substances in water by spectrophotometry at 254 nm. Quantifications were carried out for different pH values, both with and without filtration of the samples. The smallest effects were observed for unfiltered samples and neutral pH values.Fundação para a Ciência e a Tecnologia (FCT) - Project POCI-2010, measure IV.3 and reference n.º SFRH / BD / 18565 / 2004

Quantification of humic acids in surface water: effects of divalent cations, pH, and filtration

Humic acids (HAs) content of raw water is an important analytical parameter in water treatment facilities because HAs in the presence of chlorine may lead to the formation of dangerous by-products (e.g., trihalomethanes). The concentration of HAs in water is not directly accessible by common analytical methods due to their heterogeneous chemical structure. The aim of this study was to compare two methods to assess humic acids (HAs) in surface water namely absorbance of ultraviolet light at 254 nm (UV254) and total organic carbon (TOC), as well as to evaluate the effects of calcium and magnesium concentrations, pH and sample filtration on the methods’ results. An aqueous solution of a commercial HA with 10 mg L1 was used in the present work. Quantification of the HA was carried out by both UV254 and TOC (combustion-infrared method) measurements. UV254 results were converted to TOC using a calibration curve. The effects of calcium (0–136.3 mg L1) and magnesium (0–34.5 mg L1) concentrations, pH (4.0, 7.0 and 9.0) and sample filtration on UV254 and TOC measurements of the HA suspension were evaluated. More accurate TOC values of HA suspensions were obtained by the combustion-infrared method than by the UV254 absorbance method. The higher differences of TOC values between unfiltered and filtered samples were detected in the presence of calcium at pH 9.0 using the spectrophotometric method.The work described in this paper was financially supported by FCT-Foundation for Science and Technology (Portugal)-by the PhD student grant SFRH/BD/18565/2004. This support is gratefully acknowledged

Biofilms formed on humic substances : response to flow conditions and carbon concentrations

Stream biofilms are exposed to dynamic conditions of flow velocity and organic carbon availability. Thus, the aim of this study was to investigate the response of biofilms formed with and without humic substances (HSs) to an increase in flow velocity (0.04–0.10 m s-1) and HSs concentration (9.7 ± 1.0 to 19.8 ± 0.4 mg L-1 C). The highest amount of biofilm, measured as volatile suspended solids and total countable cells, was observed at 0.10 m s-1 without HSs. The bacterial community composition of the biofilm with HSs was characterized by sequences with high similarities (≥97%) to the genus Dokdonella and to the genera Comamonas, Cupriavidus and, Ralstonia. Sequences retrieved from the biofilm without HSs presented high similarities (≥97%) to the genus Sphingomonas and the genus Nitrosospira. Experimental results suggested that the presence of HSs under different concentrations and flow velocities did not significantly enhance the cell density of biofilms but influenced its microbial composition.Fundação para a Ciência e a Tecnologia (FCT) - bolsa de doutoramento SFRH/BD/18565/2004

Energy-saving wastewater treatment systems : formulation of cost functions

Natural interactions between water, soil, atmosphere, plants and microorganisms include physical, chemical and biological processes with decontaminating capacities. Natural or energy-saving wastewater treatment systems utilize these processes and thereby enable a sustainable management in the field of wastewater treatment, offering low investment and operation costs, little or no energy consumption, little and low-skill labor requirements, good landscape integration and excellent feasibility for small settlements, especially when remote from centralized sewer systems. The objective of this work is the development of cost functions for investment and operation of energysaving wastewater treatment technologies. Cost functions are essential for making cost estimations based on a very reduced number of variables. The latter are easily identified and quantified and have a direct bearing on the costs in question. The formulated investment and operation cost functions follow a power law, and the costs decrease with the increase of the population served. The different energy-saving wastewater treatment systems serving small population settlements, between 50 p.e. and 250 p.e., present associated investment costs varying from 400 e/p.e. to 200 e/p.e. and annual operation costs in the range of 70 €/p.e. to 20 €/p.e., respectively.(undefined

Fv antibodies to aflatoxin B1 derived from a pre-immunized antibody phage display library system

The production and characterization of recombinant antibodies to aflatoxin B[SUB1] (AFB[SUB1]), a potent mycotoxin and carcinogen is described. The antibody fragments produced were then applied for use in a surface plasmon resonance-based biosensor (BIAcore), which measures biomolecular interactions in 'real-time'. Single chain Fv (scFv) antibodies were generated to aflatoxin B1 from an established phage display system, which incorporated a range of different plasmids for efficient scFv expression. The scFv's were used in the development of a competitive ELISA, and also for the development of surface plasmon resonance (SPR)-based inhibition immunoassays. They were found to be suitable for the detection of AFB[SUB1], in this format, with the assays being sensitive and reproducible

Life cycle assessment of wastewater treatment options for small and decentralized communities

Sustainability has strong implications on the practice of engineering. Life cycle assessment (LCA) is an appropriate methodology for assessing the sustainability of a wastewater treatment plant design. The present study used a LCA approach for comparing alternative wastewater treatment processes for small and decentralised rural communities. The assessment was focused on two energy-saving systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge process). The low environmental impact of the energy-saving wastewater treatment plants was demonstrated, the most relevant being the global warming indicator. Options for reduction of life cycle impacts were assessed including materials used in construction and operational lifetime of the systems. A 10% extension of operation lifetime of constructed wetland and slow rate infiltration systems led to a 1% decrease in CO2 emissions, in both systems. The decrease in the abiotic depletion was 5 and 7%, respectively. Also, replacing steel with HDPE in the activated sludge tank resulted in a 1% reduction in CO2 emission and 1% in the abiotic depletion indicator. In the case of the Imhoff tank a 1% reduction in CO2 emissions and 5% in the abiotic depletion indicator were observed when concrete was replaced by HDPE.(undefined

Economic and environmental assessment of small and decentralized wastewater treatment systems

The aim of the present work was the assessment of economic and environmental aspects of decentralized energy-saving wastewater treatment systems. The formulated investment and operation cost functions were adjusted by a power law function. The different wastewater systems serving population settlements between 50 p.e. and 250 p.e., presented associated investment costs varying from €400/p.e. to €200/p.e. and annual operation costs in the range of €70/p.e.– €20/ p.e., respectively. A life cycle analysis approach was used to compare the environmental impact of alternative wastewater treatment systems. The assessment was focused on two energy-saving systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge process). Low environmental impact of energy-saving wastewater treatment systems was demonstrated, being the most relevant the global warming indicator. Options for reduction of life cycle impacts were assessed including materials used in construction and operation lifetime of the systems. A 10% extension of operation lifetime of constructed wetland and slow rate infiltration systems lead to a 5% and 7% decrease in the abiotic depletion indicator, respectively, and to a 1% decrease in CO2 emissions in both systems. Replacing steel with HDPE in the activated sludge tank resulted in a 1% reduction in CO2 emission and 1% in the abiotic depletion indicator. In the case of the Imhoff tank a 1% reduction in CO2 emissions and 5% in abiotic depletion indicator were observed when concrete was replaced by HDPE. Therefore, considering the huge potential of energy saving wastewater treatment systems, the overall environmental impact of such design alternatives should not be discarded.EU Program INTERREG III-B Atlantic Arc, Depuranat project (No. 54

Life cycle assessment of wastewater treatment options for small and decentralized communities : energy-saving systems versus activated sludge

There are several methodologies that enable direct comparison of centralized and decentralized sewage treatment systems, both in economical and ecological view. One of the latter is the so-called Life-Cycle Analysis (LCA), which accounts for the environmental impacts of a product, service, or process over the course of its life cycle. Assessed environmental impacts generally include consumption of land, energy, water, and other resources as well as the release of substances (harmful and beneficial) into air, water, and soil. LCA is largely quantitative in nature and thus can help in selecting strategies that solve environmental problems rather than merely shifting them back and forth. In the present study, an LCA comparison of several treatment processes for small and decentralized communities is made. The LCA focused on the construction, operation and disassembling phases of two energy-saving or natural systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge). The lower environmental impact of natural wastewaters treatment plants was clearly demonstrated using several ecologic indicators (e.g.: Global warming), confirming that decentralized technologies are advantageous, mainly because they require less resources