Christopher M. Sales

Nitrogen removal from raw landfill leachate by an algae-bacteria consortium

A remediation system for the removal of nitrogen from landfill leachate by a mixed algae-bacteria culture was investigated. This system was designed to treat leachate with minimal inputs and maintenance requirements, and was operated as an open semi-batch reactor in an urban greenhouse. The results of this study showed a maximum nitrogen removal rate of 9.18 mg N/(L·day) and maximum biomass density of 480 mg biomass/L. The ammonia removal rates of this culture increased with increasing initial ammonia concentration; maximum nitrogen removal occurred at an ammonia concentration of 80 mg N-NH3/L. At starting ammonia concentrations above 80 mg N-NH3/L a reduction in nitrogen removal was seen; this inhibition is hypothesized to be caused by ammonia toxicity. This inhibiting concentration is considerably higher than that of many other published studies.

Simultaneous autotrophic denitrification and nitrification in a low-oxygen reaction environment

The occurrence of autotrophic denitrification and nitrification activities by ammonia-oxidising bacteria and nitrite-oxidising bacteria is studied in a bioreactor system operable at low-dissolved oxygen (DO) and at variable oxygen influx rates. At a loading of 3.6 mg NH4(+)-N/h into the bioreactor, simultaneous autotrophic denitrification and nitrification contributed to NH4(+)-N removal over oxygen influxes of 2-14 mg O2/h and DO <0.5 mg/L. The maximum autotrophic denitrification (or total-N removal) rates were achieved in a narrow oxygen influx band of 3-5 mg O2/h, where it accounted for up to 36% of NH4(+)-N removal. At oxygen influx >16 mg O2/h and DO >2 mg/L, autotrophic denitrification ceases and roughly 90% of feed NH4(+)-N is oxidised to NOX(-)-N. The stability of total effluent chemical oxygen demand (COD) over the range of oxygen influxes tested confirms the absence of heterotrophic denitrification in the bioreactor. The long solids residence time of the stable biomass zone (21 days) led to production of effluent COD as a result of cell decay, and thus effluent COD was used to calculate more accurately the mean cell residence time.

Influence of scale on biomass growth and nutrient removal in an algal-bacterial leachate treatment system

Data collected from experiments conducted at a flask scale are regularly used as input data for life cycle assessments and techno-economic analyses for predicting the potential productivities of large-scale commercial facilities. This study measures and compares nitrogen removal and biomass growth rates in treatment systems that utilize an algae-bacteria consortium to remediate landfill leachate at three scales: small (0.25 L), medium (100 L), and large (1000 L). The medium- and large-scale vessels were run for 52 consecutive weeks as semibatch reactors under variable environmental conditions. The small-scale experiments were conducted in flasks as batch experiments under controlled environmental conditions. Kolomogov-Smirnov statistical tests, which compare the distributions of entire data sets, were used to determine if the ammonia removal, total nitrogen removal, and biomass growth rates at each scale were statistically different. Results from the Kolmogov-Smirnov comparison indicate that there is a significant difference between all rates determined in the large-scale vessels compared to those in the small-scale vessels. These results suggest that small-scale experiments may not be appropriate as input data in predictive analyses of full scale algal processes. The accumulation of nitrite and nitrate within the reactor, observed midway through the experimental process, is attributed to high relative abundances of ammonia- and nitrite-oxidizing bacteria, identified via metagenomic analysis.

Novel applications of molecular biological and microscopic tools in environmental engineering

Molecular biological methods offer flexible and powerful tools to environmental practitioners and researchers interested in studying environmental challenges in natural and engineered systems. In recent years, these techniques have allowed investigators to connect the fate, transport, and transformation of environmental chemical contaminants and pathogens with biological processes of functionally diverse microorganisms or microbial communities. Indeed, the boundaries of microbial ecosystems are constantly refined as researchers discover new links that extend beyond ————————— 1 Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095. *Corresponding author: Phone: 310-794-9850, E-mail: mahendra@seas.ucla.edu 2 Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT 84112. 3 Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA 19104 4 Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003. Bacteria to include Archaea and unicellular Eukarya. Quantitative polymerase chain reaction (qPCR) provides a rapid and sensitive approach to determine gene abundance and expression from a wide range of microorganisms from complex environments. Whole genome arrays (WGA) and functional gene arrays (FGA) are being used to elucidate transcriptional changes in response to environmental parameters. Antibiotic resistance profiling and microbial source tracking studies continue to benefit from the information provided by a molecular-based experimental design. Quantitative fluorescent in situ hybridization (qFISH) and next generation sequencing technologies are changing the way we view suspended solids in wastewater treatment. Innovative sensors are being developed that couple molecular biological, chemical, or physical properties to improve the sensitivity and specificity for intended targets. Thus, advanced molecular analysis complements conventional approaches to provide a more

Comparison of Scale in a Photosynthetic Reactor System for Algal Remediation of Wastewater

An experimental methodology is presented to compare the performance of two different sized reactors designed for wastewater treatment. In this study, ammonia removal, nitrogen removal and algal growth are compared over an 8-week period in paired sets of small (100 L) and large (1,000 L) reactors designed for algal remediation of landfill wastewater. Contents of the small and large scale reactors were mixed before the beginning of each weekly testing interval to maintain equivalent initial conditions across the two scales. System characteristics, including surface area to volume ratio, retention time, biomass density, and wastewater feed concentrations, can be adjusted to better equalize conditions occurring at both scales. During the short 8-week representative time period, starting ammonia and total nitrogen concentrations ranged from 3.1-14 mg NH3-N/L, and 8.1-20.1 mg N/L, respectively. The performance of the treatment system was evaluated based on its ability to remove ammonia and total nitrogen and to produce algal biomass. Mean ± standard deviation of ammonia removal, total nitrogen removal and biomass growth rates were 0.95±0.3 mg NH3-N/L/day, 0.89±0.3 mg N/L/day, and 0.02±0.03 g biomass/L/day, respectively. All vessels showed a positive relationship between the initial ammonia concentration and ammonia removal rate (R2=0.76). Comparison of process efficiencies and production values measured in reactors of different scale may be useful in determining if lab-scale experimental data is appropriate for prediction of commercial-scale production values.

Fructose as a novel photosensitizer: Characterization of reactive oxygen species and an application in degradation of diuron and chlorpyrifos

The objective of this study was to identify reactive oxygen species (ROS) generated from the exposure of fructose solution to the 254 nm ultraviolet (UV) light and evaluate whether fructose can be used as a photosensitizer for accelerated photo-degradation of diuron and chlorpyrifos. We demonstrated that hydrogen peroxide, singlet oxygen ((1)O2) and acidic photolysis products were generated upon UV exposure of fructose. Consistent with these findings, UV induced degradation of chlorpyrifos and diuron was accelerated by the presence of 500 mM fructose. The average first order photo-degradation rate constants in the absence and presence of 500 mM fructose were 0.92 and 2.07 min(-1) respectively for diuron and 0.04 and 0.07 min(-1) for chlorpyrifos. The quantum yields (ɸ) for direct photo-degradation of diuron and chlorpyrifos were 0.003 and 0.001 respectively. In the presence of 500 mM fructose, these values increased to 0.006 and 0.002 respectively. Thus, fructose may be an effective photosensitizer.

A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities

A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Past studies have evaluated the performance of the reactor for the removal of COD(1) and nitrogen species(2-4) by heterotrophic and chemoautotrophic bacteria, respectively. The HDBR design eliminates the requirement for external flocculation/sedimentation processes while still yielding effluent containing low suspended solids. In this study, the HDBR is applied as a photobioreactor (PBR) in order to characterize the nitrogen removal characteristics of an algae-based photosynthetic microbial community. As previously reported for this HDBR design, a stable biomass zone was established with a clear delineation between the biologically active portion of the reactor and the recycling reactor fluid, which resulted in a low suspended solid effluent. The algal community in the HDBR was observed to remove 18.4% of total nitrogen species in the influent. Varying NH4(+) and NO3(-) concentrations in the feed did not have an effect on NH4(+) removal (n=44, p=0.993 and n=44, p=0.610 respectively) while NH4(+) feed concentration was found to be negatively related with NO3(-) removal (n=44, p=0.000) and NO3(-) feed concentration was found to be positively correlated with NO3(-) removal (n=44, p=0.000). Consistent removal of NH4(+), combined with the accumulation of oxidized nitrogen species at high NH4(+) fluxes indicates the presence of ammonia- and nitrite-oxidizing bacteria within the microbial community.

Fructose Accelerates UV-C Induced Photochemical Degradation of Pentachlorophenol in Low and High Salinity Water

A novel process involving 254 nm UV-C and fructose to degrade pentachlorophenol (PCP), a pollutant, in low and high salinity (0-10 g/L salt) solutions is presented. The first order rate constants in the presence of 0, 300, and 500 mM fructose were 0.23 ± 0.04, 0.54 ± 0.01, and 1.18 ± 0.03 min(-1), respectively. Experimental evidence has shown generation of hydrogen peroxide and singlet oxygen from the UV-C exposure of fructose, which may have accelerated PCP degradation. Although salts (sodium, potassium, and calcium chloride, 1101:6.4:1) are expected to enhance the degradation rate due to generation of reactive halide species (RHS) from exposure to UV-C light, 10 g/L salt decreased the degradation rates in both the absence and presence of fructose. An LC-ESI-MS spectrum of the reaction mixture revealed a high relative abundance at m/z of 215 that corresponds to a fructose-chlorine adduct, indicating that fructose may have scavenged these RHS and prevented their reaction with PCP.

Emerging investigators series: untangling the microbial ecosystem and kinetics in a nitrogen removing photosynthetic high density bioreactor

An increasing number of water resource recovery facilities are implementing biological processes for nutrient removal and recovery. One challenge with engineering these processes is the kinetic characterization of nutrient dynamics within microbial communities, where metabolite sharing and varying ecological niches and strategies can lead to complex interactions among organisms. We have applied a 3-dimensional (3-D) visualization method to reveal the effects of varying proportions and total loading of inorganic N species (NH4+ and NO3−) on assimilatory and dissimilatory processes by a mixed photosynthetic community within a continuous high density bioreactor (HDBR). This 3-D method enabled the identification of loading conditions that result in maximum specific total N removal rates, which were not easily apparent with 1-dimensional linear regression. Furthermore, microscopic and metagenomic analyses enabled the identification of Chlamydomonas reinhardtii and Parachlorella kessleri as the two dominant algal strains and a member of the Leptolyngbya genus as the dominant cyanobacteria present within the community. Ammonia- and nitrite-oxidizing bacteria (AOB and NOB respectively) were found to comprise a small but significant portion of the bacterial community. Relative and absolute abundance of total bacteria, AOB, NOB, denitrifying bacteria, C. reinhardtii and P. kessleri were obtained from metagenomic and real-time PCR (qPCR) analyses. Within this work, we present evidence that the operational conditions and parameters of a reactor has an effect on each of the investigated components of the microbial community and that those effects ultimately impact the resultant reactor kinetics.

theseus - An R package for the analysis and visualization of microbial community data

theseus is a collection of functions within the R programming framework [1] to assist microbiologists and molecular biologists in the interpretation of microbial community composition data.