Sybil Sharvelle

Microalgae to biofuels: Life cycle impacts of methane production of anaerobically digested lipid extracted algae

This study presents experimental measurements of the biochemical methane production for whole and lipid extracted Nannochloropsis salina. Results show whole microalgae produced 430 cm(3)-CH4 g-volatile solids(-1) (g-VS) (σ=60), 3 times more methane than was produced by the LEA, 140 cm(3)-CH4 g-VS(-1) (σ=30). Results illustrate current anaerobic modeling efforts in microalgae to biofuel assessments are not reflecting the impact of lipid removal. On a systems level, the overestimation of methane production is shown to positively skew the environmental impact of the microalgae to biofuels process. Discussion focuses on a comparison results to those of previous anaerobic digestion studies and quantifies the corresponding change in greenhouse gas emissions of the microalgae to biofuels process based on results from this study.

Microbial community acclimation enhances waste hydrolysis rates under elevated ammonia and salinity conditions

Hydrolysis rates under potentially inhibitory concentrations of ammonia and salinity were investigated for two model feedstocks (manure and food waste). Rates were determined under a range of ammonia and salinity concentrations (1.0-10.0 g TAN [total ammonia nitrogen] L(-1) and 3.9-20.0 g sodium L(-1)) with unacclimated and acclimated microbial inocula. Microbial community changes as a function of acclimation and feedstock were also investigated. Using unacclimated inocula, hydrolysis was found to be severely inhibited for elevated ammonia and salinity (~4 to 10-fold, respectively) or hydrolysis was not detected. However, for inocula acclimated over 2-4 months, statistically significant inhibition generally was not detectable. Molecular analyses demonstrated that microbial community composition changed during acclimation, and bacterial communities under elevated ammonia were distinct from communities under elevated salinity. Feedstock source also had a major influence on bacterial community structure.

Biodegradation of polyalcohol ethoxylate by a wastewater microbial consortium

Polyalcohol ethoxylate (PAE), an anionic surfactant, is the primary component in most laundry and dish wash detergents and is therefore highly loaded in domestic wastewater. Its biodegradation results in the formation of several metabolites and the fate of these metabolites through wastewater treatment plants, graywater recycling processes, and in the environment must be clearly understood. Biodegradation pathways for PAE were investigated in this project with a municipal wastewater microbial consortium. A microtiter-based oxygen sensor system was utilized to determine the preferential use of potential biodegradation products. Results show that while polyethylene glycols (PEGs) were readily degraded by PAE acclimated microorganisms, most of the carboxylic acids tested were not degraded. Biodegradation of PEGs suggests that hydrophobe–hydrophile scission was the dominant pathway for PAE biodegradation in this wastewater community. Ethylene glycol (EG) and diethylene glycol (DEG) were not utilized by microbial populations capable of degrading higher molecular weight EGs. It is possible that EG and DEG may accumulate. The microtiter-based oxygen sensor system was successfully utilized to elucidate information on PAE biodegradation pathways and could be applied to study biodegradation pathways for other important contaminants.

Leachability of chemical constituents in soil–plant systems irrigated with synthetic graywater.

Over recent years, reuse of graywater for irrigation has become increasingly widespread internationally. While this practice is rapidly growing, there remain unanswered questions with respect to impacts to environmental quality and human health. The objective of this research was to determine the leachability of graywater constituents after applied to soil through a set of controlled greenhouse experiments. Four plant species including bermudagrass, tall fescue, Meyer Lemon and Emerald Gaiety Euonymus were included in the study. Three replicate columns for each species were set up and irrigated either with synthetic graywater or potable water for a 17 month duration. Leachate quality was assessed for dissolved organic carbon, nitrate, ammonium, total phosphorous, boron, sodium adsorption ratio, conductivity, surfactants, and total dissolved solids. The same constituents and also organic matter were measured in soil samples collected at the end of experiments. Phosphorus did not leach through the 50 cm deep soil columns. Salts, including boron, showed potential to leach through graywater irrigated soil. A portion of the applied nitrogen was assimilated by plants, but leaching of nitrogen was still observed as documented by statistically higher nitrogen in leachate collected from graywater-irrigated columns compared to potable water-irrigated columns (P ≤ 0.05). A low percentage of surfactants added to columns leached through (7 ± 6% on average) and a mass balance on surfactant parent compounds showed that 92–96% of added surfactants were biodegraded.

Investigation of pathogen disinfection and regrowth in a simple graywater recycling system for toilet flushing

AbstractGraywater treatment systems must inactivate pathogens, prevent regrowth, be low cost, and be simple to operate to support their widespread adoption for alleviating water stress. A treatment system comprised only of filtration and disinfection could meet these constraints. To investigate pathogen disinfection and regrowth in such a system with minimal organic matter removal, herein three disinfectants (chlorine, ultraviolet irradiation, and ozone) were tested in combination with three filter types (coarse, sand, and cartridge) for inactivation of pathogens in graywater from the showers and hand washbasins of 14 student residences. Graywater was spiked with bacterial and viral pathogens or surrogates post-filtration. Chlorination post-filtration achieved log reductions greater than 7.1, 8.0, and 7.4 for Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa, respectively, and 3.8 for MS2 bacteriophage. UV was similarly effective, but would not prevent regrowth without a disinfectant resid...

Estimation of Graywater Constituent Removal Rates in Outdoor Free-Water-Surface Wetland in Temperate Climate

AbstractAlthough constructed wetlands have become an accepted technology for the treatment of graywater for nonpotable reuse, little guidance is available on the design and sizing of wetlands specifically for graywater treatment. A common practice for sizing constructed wetlands is to apply the first order plug flow k-C* model. The objective of this work was to estimate k and C* parameters in a free-water-surface wetland processing graywater during summer, fall, and winter months for five-day biochemical oxygen demand (BOD5), total nitrogen (TN), and ammonia. Mass removal rates were consistently higher during summer months than winter months. Estimated values for k were higher in summer than winter for BOD5 (15.9  m year−1 compared to 2.5  m year−1) and TN (16.4  m year−1 compared to 5.5  m year−1). Additionally, estimates of k for BOD5 removal during all seasons was lower for graywater than typically observed for domestic and livestock wastewaters. The parameter (k and C*) estimates provided here can be ...

Decentralized Anaerobic Blackwater Management: A Sustainable Development Technology Concept for Urban Water Management

Sustainable management of water and wastewater infrastructure is essential to ensure future water quantity and quality goals are achieved. In self-sustaining decentralized wastewater management, toilet wastewater (blackwater) which contains a majority of organic material, pathogens and nutrients is separated from remaining wastewater. High organic loading in concentrated blackwater makes anaerobic digestion a feasible option for treatment. Decentralized management of blackwater using advanced reactor technologies is often considered for application in new developments and re-development projects due to localized benefits provided to the end user. Decentralized anaerobic treatment of blackwater stands out in its ability to extract and conserve green water and energy resources from blackwater and promote reuse of these resources at a local level. A demonstration scale, 95 L, upflow anaerobic sludge blanket (UASB) reactor was constructed on the Foothills Campus of Colorado State University (CSU) to treat blackwater produced in an academic research building. This demonstration scale project is a follow up to a planning study which outlined options for sustainable wastewater treatment for the CSU Foothills Campus. Results from this study intend to demonstrate the treatability of research campus blackwater in a UASB reactor and sustainable benefits ensuing from anaerobic digestion of blackwater. Treatment efficiency of the UASB was monitored in respect to reductions in chemical oxygen demand (COD), pathogens, and suspended solids. Sustainable aspects of this study include potential to offset energy input into the UASB through use of biogas produced as fuel, nutrient recovery and reuse, and disinfected effluent reuse. Data provided in this study will provide further insight into the effectiveness and safety of decentralized management of blackwater and reuse of resources contained within blackwater. It is anticipated that data will also be useful as guidance for the basis of regulations on applying advanced decentralized wastewater management systems in sustainable development projects. Such data is vital to encourage incorporation of sustainable treatment technologies as aging and failing infrastructure is rapidly becoming in need of replacement and new developments are constructed. This research is in line with recent study efforts put forth by the USEPA attempting to develop technologies and methods for new and existing developments to achieve both water and energy independence from typical centralized grid systems.

Long-Term Effects of Graywater Irrigation on Soil Quality in Arid Regions

As communities throughout the United States and abroad are becoming interested in innovative approaches to water resource sustainability, household graywater reuse for residential landscape irrigation is gaining popularity. However, the application of graywater for irrigation may result in increased levels of emerging contaminant and pathogens, negative impacts to soil quality, or potential groundwater contamination with chemical constituents present in graywater. A study is currently being conducted at Colorado State University to examine the long-term effects of graywater irrigation. The objective of this research project is to elucidate information on the fate and occurrence of graywater chemical constituents and pathogens and their long-term potential impacts on soil quality, as a result of its application for residential landscape irrigation. Sampling locations were selected to encompass a variety of soil types and climatic conditions. Soil samples were collected at four different households where graywater has been applied for irrigation for more than five years in Arizona, California, Colorado, and Texas. Soil cores were taken at depths of 0–15, 15–30, and 30–100 cm separately in both an area irrigated with graywater as well as a control area with analogous soil and landscaping that irrigated with fresh water in each site for quantification of soil physical and chemical properties, antimicrobials, surfactants, and pathogen indicator organisms. Soil samples were analyzed for pH, electrical conductivity, organic matter, total C, total N, extractable NH 4 -N, NO 3 -N, P, effectivecation exchange capacity, sodium adsorption ratio (SAR), surfactants, and antimicrobials. Widely used surfactants including linear alkyl benzene sulphonates, alcohol ethoxylates, and alcohol ether sulphates and two common antimicrobials in personal care products, triclosan and triclocarban have been quantified by liquid chromatography-mass spectrometery in soil samples. Soil samples also were analyzed for indictor organisms including total coliforms, E. coli, Enterococci, Clostridium perfringens. Results from this study will provide guidance to decision makers, water agencies, regulators, product manufactures and consumers so that safe graywater irrigation systems can be installed and operated for household landscape irrigation.

Enhanced anaerobic digestion performance via combined solids- and leachate-based hydrolysis reactor inoculation

Suboptimal conditions in anaerobic digesters (e.g., presence of common inhibitors ammonia and salinity) limit waste hydrolysis and lead to unstable performance and process failures. Application of inhibitor-tolerant inocula improves hydrolysis, but approaches are needed to establish and maintain these desired waste-hydrolyzing bacteria in high-solids reactors. Herein, performance was compared for leach bed reactors (LBRs) seeded with unacclimated or acclimated inoculum (0-60% by mass) at start-up and over long-term operation. High quantities of inoculum (∼60%) increase waste hydrolysis and are beneficial at start-up or when inhibitors are increasing. After start-up (∼112days) with high inoculum quantities, leachate recirculation leads to accumulation of inhibitor-tolerant hydrolyzing bacteria in leachate. During long-term operation, low inoculum quantities (∼10%) effectively increase waste hydrolysis relative to without solids-derived inoculum. Molecular analyses indicated that combining digested solids with leachate-based inoculum doubles quantities of Bacteria contacting waste over a batch and supplies additional desirable phylotypes Bacteriodes and Clostridia.

An Evaluation of Graywater Reuse Utilizing a Constructed Wetland Treatment System

Increasing demand for conservation of water resources has prompted the notion that the separation of graywater (all wastewater not including toilet and kitchen sources) from sewer efflu- ents through the use of dual-plumbed systems may enable graywater to be reused. Constructed wetland systems for conditioning combined wastewater effluents are widely used, and offer an ef- ficient solution for onsite wastewater treatment of a variety of pollutants. However, limited long- term research has been conducted to determine the effectiveness of such systems specifically on graywater. This paper aims to determine the viability and efficiency of constructed wetlands for graywater treatment, and assess the water quality produced from such systems. The experimental method involves monitoring of specific water quality constituents under varying operating condi- tions in a prototype constructed graywater wetland. Preliminary findings show the wetland signifi- cantly reduces many graywater contaminants including pathogens, biochemical oxygen demands, solids, and nitrogen and phosphorus species.