Lubo Liu - Academia.edu (original) (raw)

Papers by Lubo Liu

Environmental Science & Technology, Jul 14, 2006

To investigate the transport and fate of fecal pollution at Great Lakes beaches and the health ri... more To investigate the transport and fate of fecal pollution at Great Lakes beaches and the health risks associated with swimming, the near-shore waters of Lake Michigan and two tributaries discharging into it were examined for bacterial indicators of human fecal pollution. The enterococcus human fecal pollution marker, which targets a putative virulence factorsthe enterococcal surface protein (esp) in Enterococcus faecium, was detected in 2/28 samples (7%) in the tributaries draining into Lake Michigan and in 6/30 samples (20%) in Lake Michigan beaches. This was indicative of human fecal pollution being transported in the tributaries and occurrence at Lake Michigan beaches. To understand the relative importance of different processes influencing pollution transport and inactivation, a finite-element model of surf-zone hydrodynamics (coupled with models for temperature, E. coli and enterococci) was used. Enterococci appear to survive longer than E. coli, which was described using an overall first-order inactivation coefficient in the range 0.5-2.0 per day. Our analysis suggests that the majority of fecal indicator bacteria variation can be explained based on loadings from the tributaries. Sunlight is a major contributor to inactivation in the surf-zone and the formulation based on sunlight, temperature and sedimentation is preferred over the first-order inactivation formulation.

World Environmental and Water Resources Congress 2023

World Environmental and Water Resources Congress 2022

AGU Fall Meeting Abstracts, Dec 1, 2013

Miyun Reservoir, a mountain valley reservoir, is located 100 km northeast of Beijing City. Beside... more Miyun Reservoir, a mountain valley reservoir, is located 100 km northeast of Beijing City. Besides the functions of flood control, irrigation and fishery for Beijing area, Miyun Reservoir is the main drinking water storage for Beijing city. The water quality is therefore of great importance. Recently, the concentration of fecal pollution and nutrients in the reservoir are constantly rising to

Proceedings of OCEANS 2005 MTS/IEEE

The Great Lakes are a source of water for municipal, agricultural and industrial use, and support... more The Great Lakes are a source of water for municipal, agricultural and industrial use, and support significant recreation, commercial and sport fishing industries. Every year millions of people visit the 500 plus recreational beaches in the Great Lakes. An increasing public health risk has been suggested with increased evidence of fecal contamination at the shoreline. To investigate the transport and

In the momentum equations (2) and (3), horizontal mixing was described using the Smagorinsky eddy... more In the momentum equations (2) and (3), horizontal mixing was described using the Smagorinsky eddy pa-rameterization, as shown below. S = αA ∂u

The interaction between surface water and groundwater was investigated by monitoring and analyzin... more The interaction between surface water and groundwater was investigated by monitoring and analyzing the groundwater table's fluctuation in the study area, Ball Ranch of California. Based on the observed data and computer modeling results, this paper studied how groundwater was affected by the flux of the nearby San Joaquin River, precipitation, and evapotranspiration. The site is also bordered and highly influenced by the San Joaquin River located to the west of the site. The flux of the river is reflected in the monitoring wells with a noticeable lag time that was measured using a data logger. This lag time varied based upon the distance of the monitoring well from an open surface water feature such as the main pond. The water table is also affected by the recharge effects of precipitation on the site. These effects along with evapotranspiration have been taken into account while developing the mathematical model for this site. The groundwater flow direction for most of the part...

World Environmental and Water Resources Congress 2019, 2019

International Journal of Hydraulic Engineering, 2013

To investigate arsenic distribution, a prevailing problem in drinking water, arsenic concentratio... more To investigate arsenic distribution, a prevailing problem in drinking water, arsenic concentrations in the drinking water supply for the southern San Joaquin Valley were mapped to show both current and historical concentration trends. This research was also to analyze the significance of the effect of water quality and environmental factors on arsenic concentrations in groundwater. These well construction factors included the total well depth, total length of the annular seal, average screened interval depth, as well as both iron and manganese concentrations in selected wells. The results of the correlation testing between arsenic and iron and manganese concentrations provided for a very weak correlation. Correlations between the arsenic concentration and well construction were much stronger. Different statistical methods were used to test the correlations between the arsenic concentration and the three well construction parameters. Pearson's r provided the weakest correlations with the correlation coefficients of 0.2237, 0.122, and 0.228, respectively. Kendall's tau and Spearman's results show stronger correlations with coefficients of 0.302, 0.13, and 0.311. Using Spearman's rho, the correlation coefficients were 0.405, 0.155, and 0.414. Kendall's tau was not determined to be statistically significant at a 5% confidence interval for all three variables. Spearman's rho was determined to be statistically significant at a 5% confidence interval for well depth and average screened depth.

Journal of Environmental Engineering, 2002

A one-dimensional mathematical model was developed to simulate pH control using an encapsulated p... more A one-dimensional mathematical model was developed to simulate pH control using an encapsulated phosphate buffer during denitrification in a sand column. The parameters required for the model were obtained from direct physical measurement, from a tracer study to characterize the dispersion coefficient in the column, and from batch experiments designed to obtain an empirical expression describing the variation of the first-order rate constant for the encapsulated buffer core release with pH. First-order kinetic constants describing the rates of denitrification and ethanol biodegradation were obtained by fitting the model to column runs without the encapsulated buffer. With these parameters, the model was subsequently used to predict the performance of column runs containing the encapsulated buffer. Since denitrification was essentially complete in the sand columns, an increase in the effluent pH was observed. This pH increase was counteracted by the controlled release of the acidic core of the encapsulated buffers added in the columns. The model reasonably predicted the release of the encapsulated buffer core and the performance of the encapsulated buffer for controlling pH in the column.

Environmental Engineering Science, 2008

The effectiveness of novel acidic macroencapsulated buffers in controlling pH was evaluated in ba... more The effectiveness of novel acidic macroencapsulated buffers in controlling pH was evaluated in batch experiments and through detailed mathematical modeling. When exposed to a high pH solution, the macrocapsules decreased the pH to 7.5. A batch model accounting for detailed chemical equilibria was developed and used to extract the macrocapsule release kinetics within a simulated annealing algorithm. The model predicted the change in pH of the batch solutions well. The batch model was incorporated within a two-dimensional mathematical model coupling transport (convection/dispersion) and fate (including chemical reactions) of chemical species and chemical equilibrium to study the potential use of the macrocapsules in controlling pH of the groundwater in a horizontal field domain. The model was used to simulate three scenarios (reaction throughout a domain with subsequent release of base equivalents, reaction within a reactive layer with a constant release of base equivalents, and a combination of the first two scenarios), with macrocapsules added through point sources and line source. Macrocapsules are more effectively deployed as a line source as shown by the improved removal efficiency of a target contaminant. Effective life of the macrocapsule was 6 to 10 months under the conditions of the simulations.

Environmental Engineering Science, 2003

This study investigated the electrolytic method of aerating anoxic groundwater, where the goal fo... more This study investigated the electrolytic method of aerating anoxic groundwater, where the goal for aeration is to enhance in situ bioremediation by indigenous microbes. Experiments in a simulated aquifer were performed to study the electrolytic cell as an oxygen generating source, and its performance was compared to oxygen release compound (ORC ®) with respect to aerating the anoxic aquifer. Two different flow rates and concentrations of a dissolved oxygen (DO) scavenger were tested. Sodium sulfite was used to simulate the presence of DO scavengers such as Fe 21. Electrolytic aeration is possible at a current of 100 mA, and is competitive with ORC ® aeration. A higher flow rate resulted in lower dissolved DO levels in the simulated aquifer, and lower sulfite levels increased the DO levels. A mathematical model was developed to simulate the movement and dispersion of DO down-gradient of the oxygen delivery well. The model results confirmed that the two aeration technologies are comparable. The use of the model in determining the zone of influence of an electrolytic well for oxygenating an anoxic aquifer is demonstrated for a hypothetical scenario.

Journal of Environmental Engineering, 2014

Forecasting the level of waterborne bacterial pathogens (E. coli as indicator) in recreational wa... more Forecasting the level of waterborne bacterial pathogens (E. coli as indicator) in recreational waters using a deterministic model has been a very effective tool for water quality prediction and management. The fate and transport of pathogens in water is a complex process controlled by various factors of hydrodynamics, hydrology, chemistry, and microbiology. To better understand the importance of these factors and their roles in the inactivation, transport, and removal of pathogens, it is extremely important to enhance the reliability and effectiveness of a model by increasing the accuracy of simulation and prediction. This paper reports the results of sensitivity analyses on each of these factors using a calibrated hydrodynamic model coupled with a water quality model for temperature variation and E. coli transport. A nearshore region in southern Lake Michigan was used as the modeling domain in this research. Based on the sensitivity analysis method of differential analyses coupled with one-at-a-time design, the results show that the sensitivity of the different parameters can be ranked in decreasing order as follows: solar insolation, temperature correction factor, dispersion coefficients, tributary loading, wind velocity, and settling velocity. More detailed investigation of sunlight-related parameters using Chapra's formula shows that t 90 is predominant over other factors on E. coli inactivation caused by insolation. The sensitivity of sunlight-related parameters can be ranked in decreasing order as follows: t 90 , θ d , k e , α, and θ l. The model used in this study, together with the sensitivity analysis results, can be used as a reference for similar pathogen transport investigations in other freshwater bodies.

Applications in Water Systems Management and Modeling, May 2, 2018

This chapter introduces basic concepts, properties, and principles of different processes in inla... more This chapter introduces basic concepts, properties, and principles of different processes in inland surface water and analytical methodologies. The fundamentals of surface water hydrodynamics, including water properties, hydrodynamic processes, Cartesian coordinatebased governing equations, and boundary and initial conditions were reviewed. The fate and transport of contaminants in surface water were introduced. Based on aforementioned theory and principles, two hydrodynamic-water quality models were developed for studying a lake and a river, respectively. A stratified 3D model was used to investigate the circulation and E. coli transport in the nearshore region of Lake Michigan. The modeling results show that stratified phenomenon exists in the near region, and a 3D model is necessary even though a previous 2D model works well for the shallow water environment. A 2D depth-averaged water quality model was developed to estimate the fate and transport of four contaminants in the San Joaquin River of California. The modeling results indicate that it took 20 days for these contaminants to transport from the upstream to the downstream in the research domain. These models can be effectively used for inland surface water restoration and management.

Energy and Environmental Engineering

Water quality in the Three Gorges Reservoir and all its tributaries is of critical significance f... more Water quality in the Three Gorges Reservoir and all its tributaries is of critical significance for the ecological and economic development of the middle and lower Yangtze River watershed. The construction of the reservoir impoundment has caused higher water surface elevation, slower current velocity, and even backflow in its main tributaries, including the Xiangxi River. More nutrient species related to nitrogen and phosphorous are being conveyed to the water body and retained in the river's bay region much longer than previously, leading to more frequent eutrophic events such as algal blooms, and significantly threatening the downstream water quality. This study focuses on the nutrient species levels, statistically analyzing the available data to determine the effect of backflow and estimate the variation in algal levels, developing mass balances for the water budget and important contaminants, and calculating the ratio of total nitrogen to total phosphorus. Based on the data from the eutrophication processes happened in the Xiangxi River during the period from January to November 2010, total nitrogen is the limiting factor. The amount of water accumulated in the Xiangxi River was 1.108×10 10 m 3 , and the water level rose by 5.78 m from January to November 2010. Most of the phosphorus and ammonia in the river came from non-point source pollution. The results will be used to help verify and calibrate variations in the water flow rate and the associated point source and non-point source pollution. Since the Xiangxi River is a representative tributary of the Three Gorges Reservoir, the research method developed and conclusions drawn will provide a valuable reference for eutrophication investigations of other tributaries.

Journal of environmental management, Jan 8, 2017

Phosphate-Fe(II) precipitation induced by Fe(III) reduction during the anaerobic digestion of exc... more Phosphate-Fe(II) precipitation induced by Fe(III) reduction during the anaerobic digestion of excess activated sludge was investigated for the removal of phosphorus and its possible recovery. The experiments were conducted with three Fe(III) sources at 35 °C and 55 °C. The results show that ferrihydrite-Fe(III) was effectively reduced during the anaerobic sludge digestion by 63% and 96% under mesophilic and thermophilic conditions, respectively. Whereas FeCl3-Fe(III) was only mesophilically reducible and the reduction of hematite-Fe(III) was unnoticeable at either temperature. Efficient precipitation of vivianite was not observed although high saturation index values, e.g., >14 (activity reduction not considered), had been reached. This reveals the complexity of vivianite precipitation in anaerobic digestion systems; for example, Fe(II) complexation and organic interference could not be ignored. With ferrihydrite amendments at a Fe/TP of 1.5, methane production from sludge digest...

Energy and Environmental Engineering, 2014

Historical data over an 18-year-period were examined in this study in order to determine the sign... more Historical data over an 18-year-period were examined in this study in order to determine the significance and impact of an unlined landfill on groundwater. A series of constituents historically and currently detected at an unlined landfill were selected for this investigation. The data indicate that there have been a substantial decrease in the concentration of VOCs after the implementation and operation of a pump and treat system that was required by governing state agencies in a site remediation effort. The results and findings of this research indicate that the pump and treat method and the landfill gas extraction system at the Chestnut Avenue Landfill properly contained the contamination plume. All constituents detected at the site have not been detected since 2005, except that of Trichloroethene, which has been detected until recently at low concentrations. It is suggested that a different form of remediation be proposed, as the pump and treat system has been as effective as possible and further remediation of the one remaining constituent may be infeasible.