Evaluation of the Relationship between Bulk Organic Precursors and Disinfection Byproduct Formation for Advanced Oxidation Processes

Advanced oxidation processes (AOPs) are gaining traction as they offer mineralization potential rather than transferring contaminants between media. However, AOPs operated with limited energy and/or chemical inputs can exacerbate disinfection byproduct (DBP) formation, even as precursors such as dissolved organic carbon, UV254, and specific UV absorbance (SUVA) decrease. This study examined the relationship between DBP precursors and formation using TiO2 photocatalysis experiments, external AOP and non-AOP data, and predictive DBP models. The top-performing indicator, SUVA, generally correlated positively with trihalomethanes and haloacetic acids, but limited-energy photocatalysis yielded contrasting negative correlations. The accuracy of predicted DBP values from models based on bulk parameters was generally poor, regardless of use and extent of AOP treatment and type of source water. Though performance improved for scenarios bounded by conditions used in model development, only 0.5% of the model/dataset pairings satisfied all measured parameter boundary conditions, thereby introducing skepticism toward model usefulness. Study findings suggest that caution should be employed when using bulk indicators and/or models as a metric for AOP mitigation of DBP formation potential, particularly for limited-energy/chemical inputs

Investigation of methane production by anaerobic co-digestion of food waste, fats, oil and grease, and thickened waste activated sludge using automatic methane potential test system

This project investigated the methane production by anaerobic co-digestion using Automatic Methane Potential Test System (AMPTS). Food waste (FW), waste cooking oil- Canola oil (FOG), and thickened waste activated sludge (TWAS) were used as substrates for anaerobic digestion in two sets of experiments. All the substrates were digested individually in the first set of experiments. In the second set, they were combined in different proportions (four combinations) and were co-digested. All the experiments were carried at mesophilic temperature (37˚C). Results obtained from the first set established that FOG is not a suitable substrate for anaerobic digestion. From the second set of experiments, it was found that FOG did not cause inhibition. However, presence of FOG in co-digestion process caused problems which led to decreased yield of methane in all the four combinations

Phosphomolybdic Acid Catalysis of Cellulose Hydrolysis

Renewable sources such as cellulose derived biofuels are sought after in order to replace fossil fuel sources that are currently used to meet energy demands. Cellulose is a biological polymer composed of a chain of glucose molecules. Hydrolysis of cellulosic materials then has potential to serve as a source of renewable energy in the form of biofuels. The crystalline structure of cellulose is very stable, and current methods of catalyzed hydrolysis are inefficient for industrial application. This project explores the use of phosphomolybdic acid (PMA) in water to catalyze hydrolysis of microcrystalline cellulose. Temperature of hydrolysis was varied from 40 °C – 100 °C. The amount of soluble hydrolysis product was determined through wet oxidative total organic carbon analysis using a Hach method kit. Total organic carbon content is compared between equimolar amounts of PMA and sulfuric acid, the current industry preference. The yield of total organic carbon in parts per thousand (ppt) is directly correlated to increasing temperatures. Across these temperatures, PMA is more efficient than sulfuric acid in hydrolysis of cellulosic materials. Work is ongoing for glucose-specific product detection as well as evaluating the recyclability of the catalyst

Seasonal changes in the biochemical fate of carbon fixed by benthic diatoms in intertidal sediments

Benthic diatoms are important primary producers in intertidal marine sediments and form the basis of the food web in these ecosystems. In order to investigate the carbon flow within diatom mats, we performed in situ 13C pulse-chase labeling experiments and followed in detail the biochemical fate of carbon fixed by the diatoms for five consecutive days. These labeling experiments were done at approximately 2-monthly intervals during 1 yr in order to cover seasonal variations. The fixed carbon was recovered in individual carbohydrates including extracellular polymeric substances (EPS), amino acids, fatty acids, and nucleic acid bases. In addition, we assessed a variety of environmental parameters and photosynthetic characteristics. The fixed carbon was initially mainly stored as carbohydrate (glucose) while nitrogen-rich compounds (e.g., amino acids and RNA/DNA) were produced more slowly. During the year, the diatoms distributed the photosynthetically fixed carbon differently among the various carbon pools that were measured. In summer, the diatoms decreased carbon fixation and accumulated relatively more lipid as a storage compound (27% 6 2% vs. 12% 6 5% in other seasons). The percentage of fixed carbon that was excreted as EPS was lower in summer compared to other seasons, amounting 9% 6 4% and 21% 6 6%, respectively. Hence, it seemed that the physiology of the microphytobenthos was different during summer and caused by higher light intensity and a shift in nitrogen source

Geochemical reactivity of subsurface sediments as potential buffer to anthropogenic inputs: a strategy for regional characterization in the Netherlands

Geochemical reactivity of subsurface sediments as potential buffer to anthropogenic inputs: a strategy for regional characterization in the Netherland

Parameter identifiability of discrete Bayesian networks with hidden variables

Identifiability of parameters is an essential property for a statistical model to be useful in most settings. However, establishing parameter identifiability for Bayesian networks with hidden variables remains challenging. In the context of finite state spaces, we give algebraic arguments establishing identifiability of some special models on small DAGs. We also establish that, for fixed state spaces, generic identifiability of parameters depends only on the Markov equivalence class of the DAG. To illustrate the use of these results, we investigate identifiability for all binary Bayesian networks with up to five variables, one of which is hidden and parental to all observable ones. Surprisingly, some of these models have parameterizations that are generically 4-to-one, and not 2-to-one as label swapping of the hidden states would suggest. This leads to interesting difficulties in interpreting causal effects.Comment: 23 page

Temperature dependence of electrical resistivity of metals

The purpose of this investigation was to study the temperature dependence of electrical resistivity of thorium and titanium and to determine whether or not the slope of the resistance versus temperature curve of these metals exhibit anomalous discontinuities. Iron was also studied in an attempt to reproduce previously reported results on discontinuities in the slope of the resistance versus temperature curve for this metal

The NASA Astrophysics Data System: The Search Engine and its User Interface

The ADS Abstract and Article Services provide access to the astronomical literature through the World Wide Web (WWW). The forms based user interface provides access to sophisticated searching capabilities that allow our users to find references in the fields of Astronomy, Physics/Geophysics, and astronomical Instrumentation and Engineering. The returned information includes links to other on-line information sources, creating an extensive astronomical digital library. Other interfaces to the ADS databases provide direct access to the ADS data to allow developers of other data systems to integrate our data into their system. The search engine is a custom-built software system that is specifically tailored to search astronomical references. It includes an extensive synonym list that contains discipline specific knowledge about search term equivalences. Search request logs show the usage pattern of the various search system capabilities. Access logs show the world-wide distribution of ADS users. The ADS can be accessed at http://adswww.harvard.eduComment: 23 pages, 18 figures, 11 table

A Synergistic Approach to Process Innovation

With the continuing globalisation of the economy comes increasing number of competitors. Consequently, products lifecycles has continued to fall as companies strive to out-manoeuvre one another by introducing product and service innovations to meet the needs of increasingly choosy customers. This has created a business environment where change has become widespread and persistent. As processes are the engines that power organisations to deliver the values required by customers, it becomes imperative that to have competitive edge, or even survive in this sort of business environment, these processes need to be not only adaptable to the changes but also be capable of inducing the changes that would benefit the organisations. To investigate the feasibility of adaptable and change inducing processes, the research presented in this paper explores the synergies amongst three techniques for problems solving and process improvement: Theory of Inventive Problem Solving, which is more commonly known by its Russian acronym, TRIZ; Theory of Constraints (TOC); and Lean Manufacturing.N/