Owners’ Satisfaction Level with the Use of Alternative Project Delivery Methods in Water and Wastewater Infrastructures

In 2013, the American Society of Civil Engineers (ASCE) Report Card for America’s Infra-structure stated that the US needs up to $1.3 trillion in capital investments to replace the aging water pipes and repair the wastewater infrastructures. It is further believed by the industry that the streamlined approach of alternative project delivery methods, such as Design-Build (DB), and Construction Manager At-Risk (CMAR) helps ensure the economical and timely design and construction of the water and wastewater infrastructures

Inclusiveness in Teaching : Aligning Culturally Relevant Journal Articles With Course Content

The practice focuses on Inclusiveness in Water/wastewater Engineering Teaching. Upon reviewing the ethnic (Fig. below) and gender diversity (24% women) of her 57- student course on water/wastewater treatment, the Instructor replaced previously assigned articles with the reading of articles focusing on water issues affecting minoritized communities in the U.S (see references).The goal was to make students aware of water/wastewater issues facing minority communities in the US. Often, the media portrays Africa or South America as places where safe water is not available, ignoring the needs of minoritized communities in the US. A second goal was to evaluate the interest of students in this issue and determine if students of different ethnic background respond differently to questions posed about water/wastewater issues in these communities.https://digitalscholarship.unlv.edu/btp_expo/1179/thumbnail.jp

Biological reduction of perchlorate in ion exchange regenerant solutions containing high salinity and ammonium levels

The most promising technologies to remove perchlorate from water are ion exchange and biological reduction. Although successful, ion exchange only separates perchlorate from water; it does not eliminate it from the environment. The waste streams from these systems contain the caustic or saline regenerant solutions used in the process as well as high levels of perchlorate. Biological reduction could be used to treat the regenerant waste solutions from the ion exchange process. A treatment scheme, combining ion exchange and biodegradation, is proposed to completely remove perchlorate from the environment. Perchlorate-laden resins generate brines containing salt concentrations up to 6% or caustic solutions containing up to 0.5% ammonium. Both, high salt and ammonium hydroxide concentrations are potentially toxic to microorganisms. Therefore, the challenge of the proposed system is to find perchlorate reducing microorganisms that are effective under such stressful conditions. Preliminary results have shown that salt concentrations as low as 0.5% reduced the perchlorate biodegradation rate by 30%; salt concentrations greater than 1% decreased this rate to 40%. Although biodegradation was seen in ammonium levels of 0.4%, 0.6% and 1%, the perchlorate biodegradation rate was 90% of that at 0% ammonium hydroxide. Further research will focus on the isolation and/or acclimation of microorganisms that are able to biodegrade perchlorate under these stressful conditions

Energy Audit in Wastewater Aeration System

To evaluate the energy consumption air to aeration basins in wastewater treatment aeration system and to compare the standard computations of oxygen demand and blower power requirements with the actual plant data

Energy Consumption in Large Wastewater Treatment Plants as a Function of Wastewater Strength

Wastewater treatment (WWT) is an energy-intensive process. Strict standards for discharge often require energy intensive advanced treatment technologies. As a result, the number of plants using advanced treatment has increased (Figure 1). Rising energy costs and concerns about greenhouse gas generation present a major incentive for tracking energy usage of WWT. Energy usage in plant, for instance, typically represents 18 to 30% of the operational budget. Water efficient fixtures are also increasing loadings of organic matter to plants while lowering or maintaining overall liquid flow. The increased loadings have a significant impact on energy consumption. Previous work has focused primarily on aeration consumption for activated sludge rather than a plant as whole. There are very few studies that show energy requirements on a plant-wide scale with the Water Environment Federation (WEF) being one major source. This research presents a general methodology for tracking energy usage in a plant with regards to wastewater strength. It is anticipated that this research will provide a tool for designers and owners who wish to predict their energy impact before construction of a new plant or before implementing a new process on an existing plant

The carbon footprint associated with water management policy options in the Las Vegas Valley, Nevada

A system dynamics model was developed to estimate the carbon dioxide (CO2) emissions associated with conveyance of water from the water source to the distribution laterals of the Las Vegas Valley. In addition, the impact of several water management policies, including water conservation, reuse, and population growth rate change was evaluated. The results show that, at present, nearly 0.53 million metric tons of CO2 emissions per year are released due to energy use for water conveyance in distribution laterals of the Valley from Lake Mead, located 32.2 km (20 miles) southeast of the Las Vegas at an elevation of nearly 366 m (1200 ft) below the Valley. The results show that the reduction in per capita water demand to 753 lpcd by 2035 can lower the CO2 emissions by approximately 16.5%. The increase in reuse of treated wastewater effluent within the valley to 77 million cubic meters by 2020 results in the decrease of CO2 emissions by 3.6%. Similarly, change in population growth rate by ±0.5% can result in CO2 emissions reduction of nearly 12.8% by 2035 when compared to the current status

Design Aspects, Energy Consumption Evaluation, and Offset for Drinking Water Treatment Operation

Drinking water treatment, wastewater treatment, and water distribution are energy-intensive processes. The goal of this study was to design the unit processes of an existing drinking water treatment plant (DWTP), evaluate the associated energy consumption, and then offset it using solar photovoltaics (PVs) to reduce carbon emissions. The selected DWTP, situated in the southwestern United States, utilizes coagulation, flocculation, sedimentation, filtration, and chlorination to treat 3.94 m3 of local river water per second. Based on the energy consumption determined for each unit process (validated using the plant’s data) and the plant’s available landholding, the DWTP was sized for solar PV (as a modeling study) using the system advisor model. Total operational energy consumption was estimated to be 56.3 MWh day−1 for the DWTP including water distribution pumps, whereas energy consumption for the DWTP excluding water distribution pumps was 2661 kWh day−1. The results showed that the largest consumers of energy—after the water distribution pumps (158.1 Wh m−3)—were the processes of coagulation (1.95 Wh m−3) and flocculation (1.93 Wh m−3). A 500 kW PV system was found to be sufficient to offset the energy consumption of the water treatment only operations, for a net present value of $0.24 million. The net reduction in carbon emissions due to the PV-based design was found to be 450 and 240 metric tons CO2-eq year−1 with and without battery storage, respectively. This methodology can be applied to other existing DWTPs for design and assessment of energy consumption and use of renewable

Isolation of Salt Tolerant Bacteria and Investigation of Perchlorate Biodegradation at High Salinity Conditions

Perchlorate (ClO4-), known as a highly soluble oxidizer contaminant, has been detected in soil and groundwater throughout the United States for the last two decades. Biological reduction has been seen as a promising technology through which perchlorate reducing bacteria (PRB) occurring naturally in most environments utilize ClO4- as an electron acceptor. However, biological reduction of perchlorate is influenced by high salinity levels because the PRBs’ activity is hindered at salinities over 1%. The goal of this study is to investigate the impact of salinity (NaCl: 0-6.5%) on perchlorate biological reduction. Actual soil samples from the contaminated site containing PRBs were used and acclimated in broths with different salt concentrations and later the cultures were tested on their reduction abilities using perchlorate (150 mg/L) as an electron acceptor (450 mg/L) and acetate as an electron donor. Gram-staining results revealed that there has been consistent growth of salt tolerant bacteria observed at each salt concentration level (0-6.5%). The variety of bacteria are displayed with the diverse shapes present under the compound microscope, from Gram-positive bacilli to Gram-negative cocci. However, it is important to consider that the reduction kinetic is slow even as the perchlorate reduction has been observed at 6.5% NaCl concentration. This will be further studied as the experiment is still running to obtain more promising results regarding perchlorate reduction and salt tolerant bacteria isolation. The conclusion drawn so far is that there are salt tolerant bacteria in this soil which can degrade perchlorate at environments with high salt concentration.https://digitalscholarship.unlv.edu/durep_posters/1069/thumbnail.jp

The Impact of Advanced Treatment Technologies on the Engery Use in Satellite Water Reuse Plants

With an ever-increasing world population and the resulting increase in industrialization and agricultural practices, depletion of one of the world’s most important natural resources, water, is inevitable. Water reclamation and reuse is the key to protecting this natural resource. Water reclamation using smaller decentralized wastewater treatment plants, known as satellite water reuse plants (WRP), has become popular in the last decade. Reuse plants have stricter standards for effluent quality and require a smaller land footprint (i.e., real estate area). They also require additional treatment processes and advanced treatment technologies. This greatly increases the energy consumption of an already energy intensive process, accentuating even more the nexus between energy use and wastewater processing. With growing concerns over the use of nonrenewable energy sources and resulting greenhouse gas (GHG) emissions, WRPs are in need of energy evaluations. This paper contrasts the energy consumption of both conventional and advanced treatment processes in satellite WRPs. Results of this research provide a means for engineers and wastewater utilities to evaluate unit processes based on energy consumption as well as a foundation for making decisions regarding the sustainability of using advanced treatment technologies at reuse facilities

Renewable Energy Generation and GHG Emission Reduction Potential of a Satellitewater Reuse Plant by Using Solar Photovoltaics and Anaerobic Digestion

Wastewater treatment is a very energy-intensive process. The growing population, increased demands for energy and water, and rising pollution levels caused by fossil-fuel-based energy generation, warrants the transition from fossil fuels to renewable energy. This research explored the energy consumption offset of a satellite water reuse plant (WRP) by using solar photovoltaics (PVs) and anaerobic digestion. The analysis was performed for two types of WRPs: conventional (conventional activated sludge system (CAS) bioreactor with secondary clarifiers and dual media filtration) and advanced (bioreactor with membrane filtration (MBR)) treatment satellite WRPs. The associated greenhouse gas (GHG) emissions were also evaluated. For conventional treatment, it was found that 28% and 31.1% of the WRP’s total energy consumption and for advanced treatment, 14.7% and 5.9% of the WRP’s total energy consumption could be generated by anaerobic digestion and solar PVs, respectively. When both energy-generating units are incorporated in the satellite WRPs, MBR WRPs were on average 1.86 times more energy intensive than CAS WRPs, translating to a cost savings in electricity of $7.4/1000 m and$13.3/1000 m treated, at MBR and CAS facilities, respectively. Further, it was found that solar PVs require on average 30% longer to pay back compared to anaerobic digestion. For GHG emissions, MBR WRPs without incorporating energy generating units were found to be 1.9 times more intensive than CAS WRPs and 2.9 times more intensive with energy generating units. This study successfully showed that the addition of renewable energy generating units reduced the energy consumption and carbon emissions of the WRP. 3