Hydrodynamic Detachment of Deposited Particles in Fluidized Bed Filter Backwashing

TThe objective of the current study was to investigate the backwashing behavior of granular media filters used in water treatment under realistic conditions and to develop better models of the backwash process based on both fundamental and practical considerations. The focus of this study was on water only backwash but the applicability of the results to auxiliary backwash systems is discussed. The effects of filter backwash rate, coagulant used, degree of filter clogging and age of filter deposits on backwash behavior and efficiency were investigated in a pilot scale in-line filtration plant treating low turbidity raw water from a large dam. The results of these experiments and their implications both for modeling and managing filter backwash are discussed. The initial stages of backwashing are shown to be dominated by mixing and flow localization effects not accounted for in existing models of backwash. These effects appear to be dependent on both the equipment and the experimental conditions making the development of an accurate model of transient backwash behavior extremely difficult. However, it is shown that the overall efficiency of backwash can be predicted based on data about the filter and backwash design and operation that should be available at any treatment plant. This is an important first step in the development of modeling tool for the design and optimization of the complete filter cycle. A significant finding of this study was that the average age of filter deposits is one of the most important factors determining the ease with which they are detached during backwashing. Deposits become more difficult to remove the longer they remain in the filter. This has important implications for the robust design and operation of filters in applications where optimal backwash cannot be guaranteed. The rate of accumulation of mud in a filter over multiple filter cycles was determined experimentally for one set of backwash conditions and a procedure for estimating the useful life of a filter bed with sub-optimal backwash is proposed.Ph.D.Committee Chair: Dr Appiah Amirtharajah; Committee Member: Dr Carlos Santamarina; Committee Member: Dr Costas Tsouris; Committee Member: Dr Sotira Yiacoumi; Committee Member: Dr Terry Stur

The Act of Discrete Pollutant Sources on the Water Quality of Lake Lanier

Proceedings of the 1997 Georgia Water Resources Conference, March 20-22, 1997, Athens, Georgia.The potential discrete pollutant sources in the Lake Sidney Lanier watershed were identified and investigated. A sampling program was conducted to determine typical concentrations of pollutants from ten wastewater treatment facilities and from urban storm water runoff into three streams. Average yearly pollutant loadings into the lake were calculated based on the results from the sampling program and the facilities' monitoring data These calculations indicate that urban storm water runoff is a significant portion of the total loading of biochemical oxygen demand (BODO into the lake. The effluent from municipal wastewater treatment facilities comprised the significant portion of nitrogen, ammonia, and total organic carbon (TOC) loading. The loading of phosphorus was approximately equal from urban runoff and the municipal effluents. This investigation indicates that of the sources investigated, municipal wastewater treatment facilities and urban runoff can provide significant loadings of pollutants into Lake Lanier. Synthesis of this research with that of nonpoint sources of pollution will provide the basis for sound watershed management of Lake Lanier.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of Interior, Geological Survey, through the Georgia Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

Heavy Metal Loading to Lake Lanier from Point Sources of Pollution and Urban Runoff

Proceedings of the 1997 Georgia Water Resources Conference, March 20-22, 1997, Athens, Georgia.An investigation into sources of heavy metal contamination in Lake Sydney Lanier has been carried out as part of the Clean Lakes Program. Previous studies have found evidence of trace metal contamination in the water column and sediments of the lake and its tributaries and in the tissues of fish. Currently, there is little quantitative data on point and non-point sources of toxic metals in the watershed. In this study, effluent samples from nine municipal and one industrial wastewater treatment plant and stormwater samples from three lake tributaries were analyzed for total recoverable mercury, arsenic, selenium, chromium, nickel, copper, zinc, cadmium, barium and lead. The most abundant metals were barium and zinc. Toxic metal loads due to stormwater runoff were always greater than those due to effluent discharges.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of Interior, Geological Survey, through the Georgia Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

CRISPR‐Cas9 Editing of CAFFEOYL SHIKIMATE ESTERASE 1 and 2 Shows Their Importance and Partial Redundancy in Lignification in Populus tremula x P. alba

Lignins are cell-wall-located aromatic polymers that provide strength and hydrophobicity to woody tissues. Lignin monomers are synthesized via the phenylpropanoid pathway, wherein CAFFEOYL SHIKIMATE ESTERASE (CSE) converts caffeoyl shikimate into caffeic acid. Here, we explored the role of the two CSE homologs in poplar (Populus tremula x P. alba). Reporter lines showed that the expression conferred by both CSE1 and CSE2 promoters is similar. CRISPR-Cas9-generated cse1 and cse2 single mutants had a wild-type lignin level. Nevertheless, CSE1 and CSE2 are not completely redundant, as both single mutants accumulated caffeoyl shikimate. In contrast, the cse1 cse2 double mutants had a 35% reduction in lignin and associated growth penalty. The reduced lignin content translated into a four-fold increase in cellulose-to-glucose conversion upon limited saccharification. Phenolic profiling of the double mutants revealed large metabolic shifts, including an accumulation of p-coumaroyl, 5-hydroxyferuloyl, feruloyl and sinapoyl shikimate, in addition to caffeoyl shikimate. This indicates that the CSEs have a broad substrate specificity, which was confirmed by in vitro enzyme kinetics. Taken together, our results suggest an alternative path within the phenylpropanoid pathway at the level of the hydroxycinnamoyl shikimates, and show that CSE is a promising target to improve plants for the biorefinery