Municipal reclaimed water for multi-purpose applications in the power sector: A review.

Wastewater and power utilities in the United States have an enormous opportunity to collaborate on the mutually beneficial uses of reclaimed water. Despite close proximity to wastewater facilities, only a limited number of power plants are currently using municipal reclaimed water for cooling tower and boiler applications. Through a review of the literature, this document aims at creating a more perspicuous understanding of the reuse of reclaimed water for power plant applications, particularly as pertains to those associated with cooling towers and boilers, by highlighting the drivers of current implementation, regulatory issues and treatment goals, and available treatment technologies. Through an in-depth analysis of case studies, the review also highlights key examples of reclaimed water reuse projects at power utilities together with the related benefits and challenges.

Recent innovations and trends in in-conduit hydropower technologies and their applications in water distribution systems.

Water conduits have a large untapped potential to recapture energy for small hydroelectric generation, which can substantially reduce grid electricity consumption and/or provide renewable energy to water agencies. Over the past decade, there has been a recent technological renaissance in off-the-shelf "water-to-wire" turbine technologies including reaction, impulse, and hydrokinetic turbines that target the sub 1-MW in-conduit hydroelectric market. However, adoption of small hydropower technologies remain limited in water and wastewater utility sector, possibly due to the lack of market penetration and exposure. Moreover, information about newly developed small hydropower technologies in the last 5-10 years for in-conduit applications are highly dispersed in the literature. As such, this paper is a comprehensive review on recent technological innovations and trends in hydropower generation from water conduits. Sixteen turbine technologies (eight conventional turbines and eight emerging turbines) are assessed and compared based on their potential benefits and challenges, technology readiness levels, as well as potential sites for installations in diversion structures, potable and irrigation water distribution systems, and wastewater outfalls. Although conventional turbines are considered to be more robust, the modular design of the newer turbines potentially offers a more cost effective solution and better scaling-up capability. Selected case studies on the application of conventional and new turbines for pipelines are also are also reviewed and discussed.

Investigation of Cost and Energy Optimization of Drinking Water Distribution Systems.

Holistic management of water and energy resources through energy and water quality management systems (EWQMSs) have traditionally aimed at energy cost reduction with limited or no emphasis on energy efficiency or greenhouse gas minimization. This study expanded the existing EWQMS framework and determined the impact of different management strategies for energy cost and energy consumption (e.g., carbon footprint) reduction on system performance at two drinking water utilities in California (United States). The results showed that optimizing for cost led to cost reductions of 4% (Utility B, summer) to 48% (Utility A, winter). The energy optimization strategy was successfully able to find the lowest energy use operation and achieved energy usage reductions of 3% (Utility B, summer) to 10% (Utility A, winter). The findings of this study revealed that there may be a trade-off between cost optimization (dollars) and energy use (kilowatt-hours), particularly in the summer, when optimizing the system for the reduction of energy use to a minimum incurred cost increases of 64% and 184% compared with the cost optimization scenario. Water age simulations through hydraulic modeling did not reveal any adverse effects on the water quality in the distribution system or in tanks from pump schedule optimization targeting either cost or energy minimization.

Energy and water quality management systems for water utility's operations: a review.

Holistic management of water and energy resources is critical for water utilities facing increasing energy prices, water supply shortage and stringent regulatory requirements. In the early 1990s, the concept of an integrated Energy and Water Quality Management System (EWQMS) was developed as an operational optimization framework for solving water quality, water supply and energy management problems simultaneously. Approximately twenty water utilities have implemented an EWQMS by interfacing commercial or in-house software optimization programs with existing control systems. For utilities with an installed EWQMS, operating cost savings of 8-15% have been reported due to higher use of cheaper tariff periods and better operating efficiencies, resulting in the reduction in energy consumption of ∼6-9%. This review provides the current state-of-knowledge on EWQMS typical structural features and operational strategies and benefits and drawbacks are analyzed. The review also highlights the challenges encountered during installation and implementation of EWQMS and identifies the knowledge gaps that should motivate new research efforts.

nTiO2 induced changes in intracellular composition and nutrient stoichiometry in primary producer--cyanobacteria.

The widely and increasing use of nano-titanium dioxide (nTiO2) has led to its release in the environment and concerns of consequent impact on aquatic eco-relevant biota. Previous studies indicated possible physiological changes (i.e., nitrogen storage) induced by nano-titanium dioxide (nTiO2) exposure in algae, which will likely have ecological implications. This study investigated the short- (96 h) and long-term (21 days) ecotoxic impact of environmentally relevant nTiO2 concentrations on the cellular biochemical pools and nutrient stoichiometry in the nitrogen-fixing cyanobacteria Anabaena variabilis. Changes in nutrient element ratios and cellular composition were analyzed using both chemical elemental analysis and Fourier Transform Infrared (FT-IR) spectroscopy. Chemical elemental analysis showed that exposure to nTiO2 at varying dose concentrations and exposure duration led to statistically significant changes in intracellular C:N, C:P and N:P stoichiometries compared with those in the controls. In general, there seemed to be a decreasing trends of cellular C:N ratio and increase in the cellular C:P and N:P ratios with the increasing level of nTiO2 exposure. Further FT-IR analysis results revealed both temporal and dose-dependent change patterns of major macromolecules, including protein, lipids, nucleic acids and carbohydrates, in A. variabilis upon nTiO2 exposure. The relative ratio of amide II, lipids, nucleic acids and carbohydrates to the cellular protein content (quantified as amide I stretch) changed significantly within the initial 96 h of exposure and, both the magnitude of changes and levels of recovery seemed to be nTiO2 dose-dependent. This study, for the first time, demonstrated that the intracellular composition and nutrient stoichiometry changes could be induced by long-term and short-term exposures to nTiO2 to primary producers, which may have ecological implications for interspecies equilibriums and community dynamics in aquatic ecosystems.

Impact of nano titanium dioxide exposure on cellular structure of Anabaena variabilis and evidence of internalization.

The present study investigated the impact of nano titanium dioxide (nTiO(2) ) exposure on the cellular structures of the nitrogen-fixing cyanobacteria Anabaena variabilis. Results of the present study showed that nTiO(2) exposure led to observable alteration in various intracellular structures and induced a series of recognized stress responses, including production of reactive oxygen species (ROS), appearance and increase in the abundance of membrane crystalline inclusions, membrane mucilage layer formation, opening of intrathylakoidal spaces, and internal plasma membrane disruption. The production of total ROS in A. variabilis cells increased with increasing nTiO(2) doses and exposure time, and the intracellular ROS contributed to only a small fraction (<10%) of the total ROS measured. The percentage of cells with loss of thylakoids and growth of membrane crystalline inclusions increased as the nTiO(2) dose and exposure time increased compared with controls, suggesting their possible roles in stress response to nTiO(2) , as previously shown for metals. Algal cell surface morphology and mechanical properties were modified by nTiO(2) exposure, as indicated by the increase in cell surface roughness and shifts in cell spring constant determined by atomic force microscopy analysis. The change in cell surface structure and increase in the cellular turgor pressure likely resulted from the structural membrane damage mediated by the ROS production. Transmission electron microscopy (TEM) analysis of nTiO(2) aggregates size distribution seems to suggest possible disaggregation of nTiO(2) aggregates when in close contact with microbial cells, potentially as a result of biomolecules such as DNA excreted by organisms that may serve as a biodispersant. The present study also showed, for the first time, with both TEM and Raman imaging that internalization of nTiO(2) particles through multilayered membranes in algal cells is possible. Environ. Toxicol. Chem. 2011; 30:861-869. © 2010 SETAC.

Impact of titanium dioxide nanomaterials on nitrogen fixation rate and intracellular nitrogen storage in Anabaena variabilis.

This study comprehensively investigated the impact of titanium dioxide nanomaterials (nTiO(2)) exposure on cell growth, nitrogen fixation activity, and nitrogen storage dynamics in the primary producer cyanobacteria Anabaena variabilis at various dose concentrations and exposure time lengths. The results indicated that both growth rate (EC(50)-96 h of 0.62 mgTiO(2)/L) and nitrogen fixation activity (EC(50)-96 h of 0.4 mgTiO(2)/L) were inhibited by nTiO(2) exposure. The Hom's law (C(n)T(m)) was used as inactivation model to predict the concentration- and time-dependent inhibition of growth and nitrogen fixation activity. The kinetic parameters determined suggested that the time of exposure has a greater influence than the nTiO(2) concentration in toxicity. We observed, for the first time, that nTiO(2) induced a dose (concentration and time)-dependent increase in both the occurrence and intracellular levels of the nitrogen-rich cyanophycin grana proteins (CGPs). The results implied that CGPs may play an important role in the stress response mechanisms of nTiO(2) exposure and can serve as a toxicity assessment endpoint indicator. This study demonstrated that nitrogen-fixing activity could be hampered by the release of nTiO(2) in aquatic environments; therefore it potentially impacts important biogeochemical processes, such as carbon and nitrogen cycling.

Implication of using different carbon sources for denitrification in wastewater treatments.

Application of external carbon sources for denitrification becomes necessary for wastewater treatment plants that have to meet very stringent effluent nitrogen limits (e.g., 3 to 5 mgTN/L). In this study, we evaluated and compared three carbon sources--MicroC (Environmental Operating Solutions, Bourne, Massachusetts), methanol, and acetate-in terms of their denitrification rates and kinetics, effect on overall nitrogen removal performance, and microbial community structure of carbon-specific denitrifying enrichments. Denitrification rates and kinetics were determined with both acclimated and non-acclimated biomass, obtained from laboratory-scale sequencing batch reactor systems or full-scale plants. The results demonstrate the feasibility of the use of MicroC for denitrification processes, with maximum denitrification rates (k(dmax)) of 6.4 mgN/gVSSh and an observed yield of 0.36 mgVSS/mgCOD. Comparable maximum nitrate uptake rates were found with methanol, while acetate showed a maximum denitrification rate nearly twice as high as the others. The maximum growth rates measured at 20 degrees C for MicroC and methanol were 3.7 and 1.2 day(-1), respectively. The implications resulting from the differences in the denitrification rates and kinetics of different carbon sources on the full-scale nitrogen removal performance, under various configurations and operational conditions, were assessed using Biowin (EnviroSim Associates, Ltd., Flamborough, Ontario, Canada) simulations for both pre- and post-denitrification systems. Examination of microbial population structures using Automated Ribosomal Intergenic Spacer Analysis (ARISA) throughout the study period showed dynamic temporal changes and distinct microbial community structures of different carbon-specific denitrifying cultures. The ability of a specific carbon-acclimated denitrifying population to instantly use other carbon source also was investigated, and the chemical-structure-associated behavior patterns observed suggested that the complex biochemical pathways/enzymes involved in the denitrification process depended on the carbon sources used.