Monitoring the performance of wastewater treatment plants for organic matter removal using excitation-emission matrix fluorescence

This study has assessed the usefulness of excitation-emission matrix fluorescence (EEMF) as a fast and simple analytical technique to track changes in dissolved organic matter (DOM) during the sequence of treatment in wastewater treatment plants (WWTPs). Three different industrial wastewaters and treatment plants have been studied in this work: an industrial park wastewater treated in an independent line at the Burgos WWTP (Spain), a food industry wastewater (crisps and snacks manufacturing) that was treated in a MBR (Membrane Biological Reactor) pilot plant (University of Burgos) and a municipal landfill leachate treated in a physicochemical treatment plant within the same landfill. Removal percentages for the wastewater organic matter at each stage of the treatment plants were successfully obtained by monitoring the main fluorescence peaks: protein-like peaks (tryptophan-like peaks T1, T2 and tyrosine-like peaks B1, B2), humic-like peaks (fulvic-like peak A and humic-like peak C) and microbially-derived peak M. Therefore, EEMF readily allows the assessment of the reactivity of the different types of organic matter towards specific treatments, such as clarification, biodegradation, filtration, etc. Among the wastewaters studied, the food industry wastewater exhibited the greater diversity of fluorescence peaks (B1, B2, T1, T2, A1, A2 and M) whereas the landfill leachate only showed the presence of humic substances (mainly humic-like peak C). This study has demonstrated that EEMF is a useful and user-friendly technique to monitor the performance of wastewater treatment plants for organic matter removal, allowing a rapid response to potential problems in the treatment

Monitoring biological wastewater treatment processes: Recent advances in spectroscopy applications

Biological processes based on aerobic and anaerobic technologies have been continuously developed to wastewater treatment and are currently routinely employed to reduce the contaminants discharge levels in the environment. However, most methodologies commonly applied for monitoring key parameters are labor intensive, time-consuming and just provide a snapshot of the process. Thus, spectroscopy applications in biological processes are, nowadays, considered a rapid and effective alternative technology for real-time monitoring though still lacking implementation in full-scale plants. In this review, the application of spectroscopic techniques to aerobic and anaerobic systems is addressed focusing on UV--Vis, infrared, and fluorescence spectroscopy. Furthermore, chemometric techniques, valuable tools to extract the relevant data, are also referred. To that effect, a detailed analysis is performed for aerobic and anaerobic systems to summarize the findings that have been obtained since 2000. Future prospects for the application of spectroscopic techniques in biological wastewater treatment processes are further discussed.The authors thank the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors also acknowledge the financial support to Daniela P. Mesquita and Cristina Quintelas through the postdoctoral Grants (SFRH/BPD/82558/2011 and SFRH/BPD/101338/2014) provided by FCT - Portugal.info:eu-repo/semantics/publishedVersio

Applications of natural organic matter optical properties for assessing drinking water disinfection and distribution

The task of providing safe drinking water requires proper monitoring of water quality and treatment performance from source to tap. Accordingly, the demand for online monitoring is increasing both at treatment plants a nd within distribution networks. Some of the available techniques use correlations between the optical properties of dissolved organic matter (DOM), mainly absorbance, and other water quality parameters. Fluorescence spectroscopy is significantly more sensitive than absorbance spectroscopy and gives comprehensive information about the composition and concentration of organic matter, so it has a strong potential for online monitoring applications. In this thesis, the application of fluorescence spectroscopy was investigated for two locations in the drinking water treatment system: the ultraviolet (UV) disinfection chambers and the distribution network. With respect to UV254disinfection, fluorescence spectroscopy was investigated as a proxy of potential unwanted by-products (assimilable organic carbon (AOC) and disinfection by products (DBPs), in addition to the administered UV dose. The UV254 irradiation increased assimilable organic carbon (AOC) concentration, with the estimated AOC production induced by UV254irradiation at a dose of 40 mJ cm-2being 0.4 % of the dissolved organic carbon. The concentration of adsorbable organic chlorine (AOCl), a subset of adsorbable organic halogens (AOX), generally increased following UV254 irradiation at the typical disinfection dose. Weak but statistically-significant correlations were found between the UV-induced fluorescence reduction and increases in both AOC and AOCl concentrations. Compared to absorbance, greater reductions were observed in fluorescence intensity following sequential UV irradiation and chlorination and these correlated more strongly with AOCl production. Following UV254disinfection, a linear relationship was observed between UV254dose and changes in long-wavelength fluorescence (> 400 nm) intensities at doses up to 200 mJ cm-2. However, the application of fluorescence as a proxy of the UV254dose is limited due to the relatively small and unpredictable direction of change of fluorescence intensity. In the distribution network, the sensitivity of fluorescence to detect contamination caused by entrainment was compared to the sensitivity of other common water quality parameters including several trace elements and microbial indicator species abundances. Of these, fluorescence was the most sensitive tracer for distinguishing contamination from natural variation, followed by absorbance. The relationship between fluorescence and microbial regrowth was also examined; however, no correlation was observed. The results of this thesis imply that although fluorescence might not always correlate with the chemical and microbial water parameters, its prompt response to treatment-induced modifications and fluctuations, together with high analytical precision and sensitivity of fluorescence measurements, make it a useful parameter for real-time monitoring of water quality changes in drinking water treatment plants and distribution systems

Assessment and characterization of dissolved organic nitrogen removal in simulated soil aquifer treatment systems

Treated wastewater (reclaimed water) is becoming more critical as an alternative water source due to population growth and extreme precipitation patterns. The more we rely on water reuse schemes, the more we have to expand our knowledge about the efficiency of treatment processes. As part of the water reuse programs, soil aquifer treatment systems are widely applied to enhance groundwater resources and the quality of treated wastewater by providing environmental barriers, including soil and water. There have been decades of applied research on different types of soil/aquifer-based treatment systems focusing on their operation and maintenance as well as their capability to remove contaminants. However, considering the fact that the list of contaminants of concern are continually developing and these systems are highly site-specific, there is always a need to understand better the fate of compounds that can act as a contaminant themselves in specific doses or become pre-cursors of other contaminants.Therefore, this research focused on dissolved organic nitrogen (DON) that has yet to be adequately investigated. Effluent DON could be problematic in the receiving waters as a nitrogen source causing eutrophication. It can also act as a precursor for nitrogenous disinfection by-products. In this study, we used unsaturated soil columns to simulate the vadose zone treatment systems in the lab. We simulated field characteristics by using the soil from the vadose of effluent rapid infiltration basins and reclaimed water from a full scale water reclamation rather than artificial wastewater. We observed steady DON removal in the columns for more than a year and a half, as well as the improvement of water quality through the removal of other organic compounds. Since N-Nitroso-dimethylamine (NDMA), one of the nitrogenous disinfection by-products, concentrations were pretty low in our feed reclaimed water, and we did not reach conclusive results about the columns’ capability of further removal of NDMA. However, our results showed that the columns could remove NDMA precursors by removing the reclaimed water organic matter. In addition, we characterized the organic matter in the reclaimed water applied to the columns using fluorescence spectroscopy EEM spectra. EEM spectra analysis has been widely used for organic matter characterization in drinking or surface water. Here, we focused on its capability to monitor the performance of soil aquifer treatment systems. We were able to detect humic-like, fulvic-like, and tyrosine-like compounds in the influent and effluent of the columns using the fluorescence regional technique. We followed their change through the columns and found that most of the DON removal was attributed to humic-like compounds, even though the removal was observed in different defined regions. We fitted a PARAFAC model with four components to our data that was able to be compared with other models across different aquatic systems. The main component of the model (C1) was attributed to the aromatic molecules of terrestrial origin and associated with humic-like compounds. Another detected component (C3) corresponded with microbial humic-like and terrestrially delivered and was reported at drinking water treatment plants. The results confirmed the capability of EEM spectra as a monitoring tool for the organic material and that its potential should be further investigated in the lab and field-scale soil aquifer treatment systems under different hydrogeological conditions, operation and maintenance techniques, and source water quality

Fluorescence spectroscopy for wastewater monitoring: A review

© 2016. Wastewater quality is usually assessed using physical, chemical and microbiological tests, which are not suitable for online monitoring, provide unreliable results, or use hazardous chemicals. Hence, there is an urgent need to find a rapid and effective method for the evaluation of water quality in natural and engineered systems and for providing an early warning of pollution events. Fluorescence spectroscopy has been shown to be a valuable technique to characterize and monitor wastewater in surface waters for tracking sources of pollution, and in treatment works for process control and optimization. This paper reviews the current progress in applying fluorescence to assess wastewater quality. Studies have shown that, in general, wastewater presents higher fluorescence intensity compared to natural waters for the components associated with peak T (living and dead cellular material and their exudates) and peak C (microbially reprocessed organic matter). Furthermore, peak T fluorescence is significantly reduced after the biological treatment process and peak C is almost completely removed after the chlorination and reverse osmosis stages. Thus, simple fluorometers with appropriate wavelength selectivity, particularly for peaks T and C could be used for online monitoring in wastewater treatment works. This review also shows that care should be taken in any attempt to identify wastewater pollution sources due to potential overlapping fluorophores. Correlations between fluorescence intensity and water quality parameters such as biochemical oxygen demand (BOD) and total organic carbon (TOC) have been developed and dilution of samples, typically up to ×10, has been shown to be useful to limit inner filter effect. It has been concluded that the following research gaps need to be filled: lack of studies on the on-line application of fluorescence spectroscopy in wastewater treatment works and lack of data processing tools suitable for rapid correction and extraction of data contained in fluorescence excitation-emission matrices (EEMs) for real-time studies

Physical-chemical treatment of landfill leachate : technological performance, spectral characterization and cost estimations

The generation of landfill leachate is a significant result of landfilling. Because of the high concentrations of pollutants in leachate, disposal of raw or insufficiently treated landfill leachate can cause harm to the environment. Biological processes are inefficient for the treatment of stabilized landfill leachate given the presence of recalcitrant organic compounds and low leachate biodegradability. As such, post-treatment is required to meet discharge standards. Therefore, this PhD thesis focused on the (post)-treatment of raw and biologically treated landfill leachate using four physical-chemical processes, i.e. ozonation, coagulation-flocculation, granular activated carbon (GAC) adsorption, and ion exchange. The aim was obtaining an optimized and cost effective integrated leachate treatment train. The research also used spectral and chemometric techniques to characterize dissolved organic matter (DOM) components in landfill leachate and to monitor how they are removed during treatment. The results show that (post)-treatment of raw and biologically treated leachate with a single physical-chemical step is inefficient as the environmental discharge standards are not met. However, combining coagulation-flocculation or ozonation with GAC adsorption significantly reduces the pollutant concentrations making it possible to meet the discharge standards. Spectral and chemometric analysis show that coagulation as a pre-treatment step removes high molecular weight humic compounds that would otherwise clog the GAC adsorption sites, and that GAC unselectively removes DOM components hereby improving the overall performance. Ion exchange can be used to recover ammonium from the raw landfill leachate with complete removal. Overall, (post)-treatment of raw and biologically treated leachate with coagulation-flocculation + GAC + ion exchange and coagulation-flocculation + GAC, respectively, are shown to be more efficient and cost effective than a treatment train without coagulation-flocculation pre-treatment

Characterization and Differentiation of Wastewater Effluent Organic Matter (EfOM) Versus Drinking Water Natural Organic Matter (NOM): Implications for Indirect Potable Reuse

A major objective of this research was to investigate the characteristic differences/similarities between wastewater effluent organic matter (EfOM) and drinking water natural organic matter (NOM) derived from diverse water sources using multiple analytical and statistical techniques. Parallel factor analysis (PARAFAC), a three-dimensional statistical modeling technique, was applied to a dataset of excitation-emission matrix (EEM) of fluorescing organic matter components in order to identify organic matter fluorophores characteristic of EfOM versus NOM. Identified fluorophores were used to elucidate characteristic features of bulk organic matter as well as treatability of EfOM(-impacted waters) by conventional drinking water treatment processes. Results show that EfOM exhibits increased fractions of microbial-originated organic components of a hydrophilic nature. Size exclusion chromatographic (SEC) characteristics of EfOM and NOM reveal that EfOM is a mixture of various organic components which have different molecular weight distributions and light-absorbing properties. Incorporation of traditional NOM characterization results with multivariate statistical analyses shows that a hydrophilic fraction is a key discriminator of EfOM that differentiates it from NOM, and thus, the organic properties of any water source influenced by wastewater may be shifted to a more hydrophilic nature.The evaluation of wastewater impacts on existing drinking water treatment plant in terms of treatability of an organic matter was also an aim of this study. Lab-scale simulations of the coagulation process suggest EfOM has potentially negative impacts on drinking water treatment efficiency due to changed organic properties of source waters. Consequently, adoption of a biodegradation process such as soil aquifer treatment (SAT) or river bank filtration (RBF) is proposed as a strategic management

Instrumentation and control of anaerobic digestion processes: a review and some research challenges

The final publication is available at Springer via http://dx.doi.org/10.1007/s11157-015-9382-6[EN] To enhance energy production from methane or resource recovery from digestate, anaerobic digestion processes require advanced instrumentation and control tools. Over the years, research on these topics has evolved and followed the main fields of application of anaerobic digestion processes: from municipal sewage sludge to liquid mainly industrial then municipal organic fraction of solid waste and agricultural residues. Time constants of the processes have also changed with respect to the treated waste from minutes or hours to weeks or months. Since fast closed loop control is needed for short time constant processes, human operator is now included in the loop when taking decisions to optimize anaerobic digestion plants dealing with complex solid waste over a long retention time. Control objectives have also moved from the regulation of key variables measured online to the prediction of overall process perfor- mance based on global off-line measurements to optimize the feeding of the processes. Additionally, the need for more accurate prediction of methane production and organic matter biodegradation has impacted the complexity of instrumentation and should include a more detailed characterization of the waste (e.g., biochemical fractions like proteins, lipids and carbohydrates)andtheirbioaccessibility andbiodegradability characteristics. However, even if in the literature several methodologies have been developed to determine biodegradability based on organic matter characterization, only a few papers deal with bioaccessibility assessment. 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Influence of Land Use, Land Cover, and Hydrology on the Spatial and Temporal Characteristics of Dissolved Organic Matter (DOM) in Multiple Aquatic Ecosystems

Spatial and temporal patterns of dissolved organic matter (DOM) were characterized using a combination of spectroluorometric measurements and multivariate analysis techniques. The study was conducted over a four-year (2012-2016) period in multiple watersheds located in the Gulf-Atlantic Coastal Plain Physiographic region of the southeast USA as well as in the Indo-Gangetic Plain of India. Surface water samples were collected from five major lakes in the Mississippi, an estuarine region in the southeastern Louisiana, and from the coastal region in the eastern Mississippi Sound in the USA, and a large river (Ganges River) in India. Absorption and fluorescence measurements were performed to generate absorption spectra and excitation-emission matrices (EEMs). Using parallel factor analyses (PARAFAC), EEM models were developed to characterize the biogeochemistry of DOM in three studies in this project. Principal component analysis and regression analyses of DOM data indicated that the northern Mississippi lakes were majorly influenced by agricultural land use, estuarine region was affected by natural DOM export from forests and wetlands, while the coastal waters were affected by a mix of anthropogenic and natural inputs of DOM. Spatial analyses indicated that DOM derived from watershed with increased wetland coverage was humic and aromatic while the DOM derived from agricultural watersheds was bioavailable. Temporal patterns of DOM in the estuary indicated the influence of hydrologic conditions and summer temperatures, and revealed strong seasonality in DOM evolution in the watershed. During high discharge periods (spring), aromatic and humic DOM was exported from the watershed while strong photochemical degradation during summer resulted bioavailable DOM. Comparison between two river systems, a highly urbanized large river and a small pristine river, indicated the influence of anthropogenic inputs of DOM in the large river system. DOM was bioavailable during summer due to anthropogenic activities in the large river system while it varied with hydrological connectivity in a small river system during summer and winter. In conclusion, this study has improved my understandings of the DOM properties, which are critical for a comprehensive assessment of biogeochemical processes undergoing in important water bodies on which our society is heavily dependent upon

Assessing and optimizing biofilter performance in drinking water treatment

Biological filtration is a widely used treatment barrier in drinking water treatment plants to ensure the biological stability of treated water in distribution systems. Biofilters remove particulate and dissolved organic matter (DOM) and biodegradable organic matter from water. However, biofilters are difficult to study at full-scale where they are influenced by many factors that vary over time. Furthermore, there are multiple DOM removal processes occur simultaneously within BAC filter biofilms including adsorption, desorption and biodegradation. This research examined how optical properties of DOM (e.g. fluorescence spectroscopy and absorbance) can be used as an advanced characterization method to provide novel insights into performance and fundamental mechanisms of drinking water treatment via biological filtration processes.A full-scale study involving experimental manipulation of parallel biofilters with non-adsorptive media allowed the study of DOM removal as a function of empty bed contact time (EBCT). By continuously monitoring effluent turbidity from the filters and measuring DOM removal via fluorescence spectroscopy, it was shown that turbidity and protein-like DOM removal increased linearly with increasing EBCT up until at least 80 min EBCT. Removal of refractory humic-like DOM removal improved, although to a smaller extent. This was contrary to the prevailing view that there is a negligible improvement in DOM removal efficiency at contact times longer than 30 min. Striking a good balance between DOM removal by biofiltration and the cost of longer EBCT can in turn result reduced operational costs while improving finished water quality.This research was also carried out to distinguish biotic (biological degradation) and abiotic (adsorption and desorption) processes occurring within biofilter media. To distinguish these requires a suitable abiotic control, i.e. filter media with the same chemical properties but no biology. To identify abiotic controls for BAC filter experiments, a batch-scale study was conducted using gamma irradiation as a sterilization method. However, by measuring DOM removal via fluorescence spectroscopy, it was possible to observe that the chemical properties of biofilter materials changed even at low gamma doses (2.5 kGy) and a dose-related release of protein-like fluorophores occurred, possibly from the biofilm. The gamma-irradiation method was therefore deemed to be unsuitable for producing abiotic controls for BAC studies.In a further attempt to identify abiotic controls for BAC filter experiments, the temperature was utilized as an alternative control strategy. Depending on responses to temperature in batch experiments, it was deduced whether DOM removal predominantly occurred via adsorption (chemisorption/physisorption) or biological degradation. Under the particular experimental conditions, there was little evidence of biological removal; instead, removal of DOM fractions emitting at longer wavelengths (“humic-like”, >430 nm) was consistent with chemisorption,viremoval of DOM emitting at intermediate wavelengths (“humic-like”, 390-420 nm) was consistent with physisorption, and multiple mechanisms were indicated for “protein-like” (<380 nm) DOM. Abiotic mechanisms like adsorption are often assumed to be unimportant for aged BAC filters; however, these results suggest that abiotic processes may be important for some DOM fractions.Ultimately, this research aims to inform the design and operation of full-scale biological filters under Nordic climate conditions. To that end, a simple and cost-effective operational strategy was investigated for improving short-term DOM removal in full-scale biological filters. The strategy involved replacing a small fraction of saturated filter media with new media. Relative to replacing the entire media, this approach required lower capital cost and shorter downtime and maintained conditions for biological filter functioning. The modified biological filters showed improved DOM removal lasting for several weeks.The results of this thesis demonstrate that fluorescence spectroscopy, due to high analytical precision and sensitivity, is a sensitive method for tracking DOM removal via biological filters. Additionally, it suggests there are opportunities to improve drinking water treatment by promoting one or other of the removal mechanisms depending on the incoming water quality. For example, allowing longer contact time in summer when there is elevated biodegradable DOM removal or performing partial renewal of biofilter media after heavy rains when incoming water has relatively high organic pollutants. Overall, these results are relevant to water producers that aim to optimize biofilters performance under strained operating conditions