Srinivas Panguluri

Transformation of silver nanoparticles in fresh, aged, and incinerated biosolids

The purpose of this research was to assess the chemical transformation of silver nanoparticles (AgNPs) in aged, fresh, and incinerated biosolids in order to provide information for AgNP life cycle analyses. Silver nanoparticles were introduced to the influent of a pilot-scale wastewater (WW) treatment system consisting of a primary clarifier (PC), aeration basin, and secondary clarifier. The partitioning of the AgNPs between the aqueous and solid phases in the system was monitored. Less than 3% of the total AgNPs introduced into the PC were measured at the overflow of the PC. Biosolids were collected from the pilot-scale system for silver analyses, including Ag concentration and speciation. Additionally, biosolids were collected from a publically owned treatment works (POTW). The POTW biosolids were spiked with AgNPs, AgNO3, and Ag2S. One set of the spiked POTW biosolids was aged for one month, and another set was analyzed within 24 h via X-ray absorption spectroscopy (XAS) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) in order to determine Ag chemical speciation and elemental associations. Replicates of the aged and 24-h samples were also incinerated at 850 °C for 4 h. The residual ash was analyzed by XAS and SEM-EDX. The results show that AgNPs are converted to Ag-sulfur (as sulfide and sulfhydryl) species in fresh and aged biosolids, which is in agreement with other studies on AgNPs in biosolids. Results from linear combination fitting of the XAS data for incinerated biosolids show that a significant proportion of the spiked silver (30-50%) is converted to elemental Ag in the incineration process. In addition to elemental Ag, the results suggest the presence of additional Ag-S complexes such as Ag2SO4 (up to 25%), and silver associated with sulfhydryl groups (26-50%) in the incinerated biosolids. Incinerated biosolids spiked with AgNO3 and Ag2S exhibited similar transformations. These transformations of AgNPs should be accounted for in life-cycle analyses of AgNPs and in management decisions regarding the disposal of incinerated biosolids.

Polymorph-dependent titanium dioxide nanoparticle dissolution in acidic and alkali digestions

Multiple polymorphs (anatase, brookite and rutile) of titanium dioxide nanoparticles (TiO2-NPs) with variable structures were quantified in environmental matrices via microwave-based hydrofluoric (HF) and nitric (HNO3) mixed acid digestion and muffle furnace (MF)-based potassium hydroxide (KOH) fusion. The environmental matrices included stream bed sediments, kaolinite and bentonite. The percentage of titanium (Ti) recovered from the mixed acid digestion was not statistically different from KOH fusion when anatase and brookite TiO2-NPs were blended in all three environmental matrices. However, the percentage of Ti recovery of rutile TiO2-polymorph from the samples digested using the mixed acid digestion method was significantly lower [23 (±5), 12 (±6), 11 (±0.6)] than those digested using KOH fusion method [74 (±4), 53 (±7), 75 (±2)]. The recovery percent values reported are for Ti in sediment, kaolinite, and bentonite matrices, respectively. Exposing the TiO2-NP spiked samples to elevated heat and pressure reduced the recovery of Ti from all three polymorphs via mixed acid digestion. In contrast, Ti recoveries from KOH fusion improved after heat and pressure treatment. A narrowing of the X-ray diffraction (XRD) peaks for anatase and brookite after heat and pressure treatment indicated an increase in the aggregation or particle interaction of the TiO2-NPs. The XRD peaks for rutile TiO2-NP polymorph was similar before and after heat and pressure treatment. In summary, regardless of the selected environmental matrix type, the mixed acid digestibility of TiO2-NPs is polymorph-dependent; whereas, the KOH-fusion digestibility is polymorph independent. Therefore, when analyzing environmental samples containing TiO2-NPs with unknown polymorphs, a KOH-fusion digestion method is recommended for yielding consistent results.

Using Continuous Monitors for Conducting Tracer Studies in Water Distribution Systems

The use of online monitors for conducting a distribution system tracer study is proving to be a helpful tool to accurately understand the flow dynamics in a distribution system. In a series of field tests sponsored by the U. S. Environmental Protection Agency (EPA) and the Greater Cincinnati Water Works (GCWW) in 2002-2003, a food-grade calcium chloride tracer was introduced into a water system network and the movement of the chemical was traced using strategically placed automated online conductivity meters (in conjunction with a limited grab sampling program). The benefits and results of this field testing effort are discussed in this paper. Disclaimer This paper has been reviewed in accordance with the EPAs peer and administrative review policies and approved for presentation and publication. The mention of trade names or commercial products in this paper does not constitute

Tracer Dispersion Studies for Hydraulic Characterization of Pipes

1. Shaw Environmental, Inc., 5050 Section Avenue, Cincinnati, OH 45212; PH (513) 782-4893; FAX (513) 782-4663; email: Srinivas.Panguluri@shawgrp.com 2. U. S. Environmental Protection Agency, ORD/NRMRL/WSWRD, 26 W. Martin Luther King Drive, Cincinnati, OH 45268; PH (513) 569-7655; FAX (513) 569-7185; email: Yang.Jeff@epa.gov 3. U. S. Environmental Protection Agency, ORD/NRMRL/WSWRD, 26 W. Martin Luther King Drive, Cincinnati, OH 45268; PH (513) 569-7067; FAX (513) 569-7185; email: Haught.Roy@epa.gov 4. RM Clark Consulting Engineer; 9627 Lansford Drive, Cincinnati, OH 45242; PH (513) 891-1641; FAX (513) 891-2753; email: rmclark@fuse.net 5. Shaw Environmental, Inc., 5050 Section Avenue, Cincinnati, OH 45212; PH (513) 782-4730; FAX (513) 782-4663; email: Radha.Krishnan@shawgrp.com 6. Shaw Environmental, Inc., 5050 Section Avenue, Cincinnati, OH 45212; PH (513) 782-4974; FAX (513) 782-4663; email: Don.Schupp@shawgrp.com

Chlorine Decay and DBP Formation under Different Flow Regions in PVC and Ductile Iron Pipes: Preliminary Results on the Role of Flow Velocity and Radial Mass Transfer

A systematic experimental study was conducted using a pilot-scale drinking water distribution system simulator to quantify the effect of hydrodynamics, total organic carbon (TOC), initial disinfectant levels, and pipe materials on chlorine decay and disinfection by-product (DBP) formation. The first phase of the experiments focused on the variables of flow rate and pipe materials and their effects on the formation of trihalomethanes (THMs) a primary category of DBPs in chlorinated drinking water. Different from previously reported bench-scale investigations, this experimental study was to determine chlorine decay and DBP formation kinetics under simulated field conditions and to contrast the effects of new PVC and aged ductile iron pipe materials. In this paper, we report the experimental findings on the rate of THM formation under stagnant, laminar, transitional and turbulent conditions, and further attempt to address the effects of the pipe materials on the reaction kinetics. The results indicate that the second-order DBP formation model of Clark (1998) can sufficiently describe the variations in total trihalomethanes (TTHM) concentrations. The determined reaction constants are smaller under stagnant and turbulent flows in the new PVC pipes than the aged ductile iron pipe. The latter has a high rate of DBP formation accompanying with rapid chlorine residual loss. It is suggested that these observed differences are a result of the mass-transfer enhanced wall demand in the aged ductile iron pipe. Implications for re-chlorination in the distribution network operations are discussed.

Real-Time Remote Monitoring of Drinking Water Quality

Over the past eight years, the U.S. Environmental Protection Agency’s (EPA) Office of Research and Development (ORD) has funded the testing and evaluation of various online “real-time” technologies for monitoring drinking water quality. The events of 9/11 and subsequent threats to the nation’s infrastructure have expanded the focus of this research. Currently, EPA’s National Homeland Security Research Center (NHSRC) is funding additional research to evaluate a variety of remote water quality monitoring (RWQM) technologies. The evaluations focus on the ability of the commercially available technologies to be used as a tool to detect deliberate or accidental contamination of water supply and water distribution systems. This paper highlights some of the lessons learned from the past and ongoing research related to RWQM conducted by EPA at the EPA’s Test and Evaluation (T&E) Facility in Cincinnati, Ohio, and other field locations. Disclaimer This paper has been reviewed in accordance with the EPAs peer and administrative review policies and approved for presentation and publication. The mention of trade names or commercial products in this paper does not constitute endorsement or recommendation for use by the authors, or by their respective employers. The trade names have been included to accurately represent the equipment used for the purpose of testing and evaluation.

Creating a Cyber Security Culture for Your Water/Waste Water Utility

Water is a vital resource. In the Water Sector, the U.S. Environmental Protection Agency (EPA) is the lead agency for protecting the critical infrastructure. The EPA has determined that a voluntary approach to cyber security is sufficient for protecting critical infrastructure in this sector. Also, the EPA is in collaborative partnership with the Department of Homeland Security (DHS) to ensure cyber security in this sector. In 2014, the DHS responded to 14 cyber security incidents reported by the Water Sector. The established techniques of cyber-attacks are documented in this chapter along with a summary of common vulnerabilities. A sector-specific example of a secure-network design architecture is presented and discussed in this chapter. However, the variability of organizational size and availability of resources in this sector makes a template technological approach difficult to implement. While understanding the technological approaches including hacking tools and defense in depth are important countermeasure mechanisms, a cultural approach is necessary to control the human element which makes the selected technological approach a viable measure.

CONDITION ASSESSMENT MODELING FOR DRINKING WATER DISTRIBUTION SYSTEMS: AN EXAMPLE OF SHARED FRAILTY ANALYSIS

It has been estimated that replacement of drinking water infrastructure will need to increase from the current estimated replacement rate of 0.3 percent per year to 2.0 percent per year by 2040 in order to meet the needs of US drinking water utilities. This is approximately four times the current replacement rate. In addition to maintenance, structural and regulatory issues, there is concern over the ability of US drinking water distribution systems to maintain water quality to the consumer. Consequently, drinking water utilities are increasingly interested in the potential for the application of techniques such as Condition Assessment (CA) methodology for managing drinking water infrastructure. The USEPA has therefore initiated a project (carried out by the Eastern Research Group) with the goal of developing new CA techniques that can assist utilities in dealing with some of these issues. Several tools have been developed (which will be discussed) including a modeling approach that can be applied to a drinking water utilities break and leak database and that will help managers understand the factors affecting the “survival” of drinking water pipe sections. The model is based on the application of the Cox Proportional Hazard Model (CPHM) modified by a frailty function. Shared frailty represents unobserved external factors, known to be important, which vary randomly and which are more consistent among sections in the same pipe run than among sections in different pipe runs. Examples of factors which may be represented in this way are soil corrosivity, variations in external mechanical loading, pressure transients, vibration, nearby construction, etc. The CPHM has been applied to a pipe break data base collected by the Laramie Water Utility (located in Laramie, Wyoming (USA)). Preliminary results, for example, indicate that, on the average, metallic pipe has fewer beaks than Poly Vinyl Chloride (PVC) pipe but is more subject to undefined random factors. That is, metallic pipe has more “random frailty” then PVC pipe. This has implications for infrastructure management policies such as the application of advanced monitoring techniques and replacement strategies. In addition to the CPHM for individual pipe sections a general pipe break model has been developed.

CONTROLLING DISINFECTION RESIDUAL LOSSES IN DRINKING WATER DISTRIBUTION SYSTEMS: RESULTS FROM EXPERIMENTAL STUDIES

It has become generally accepted that water quality can deteriorate in a distribution system through reactions in the bulk phase and/or at the pipe wall. These reactions may be physical, chemical and/or microbiological in nature. Perhaps one of the most serious aspects of water quality deterioration in a network is the loss of the disinfectant residual that can weaken the barrier against microbial contamination. Studies have suggested that one factor contributing to the loss of disinfectant residuals is the reaction between bulk phase disinfectants and pipe wall material. Free chlorine loss in corroded metal pipes, subject to changes in velocity, was assessed during an experiment conducted under controlled conditions in a specially constructed pipe loop located at the U.S Environmental Protection Agency’s ( EPA’s) Test and Evaluation (T&E) Facility in Cincinnati, Ohio (USA). These studies demonstrated that in older unlined metal pipes, the loss of chlorine residual increases with flow. Additional experimental studies are currently being conducted by the USEPA. They are intended to study the effect of hydrodynamics on disinfectant residual wall demand as well as the effect of total organic carbon, initial disinfectant levels, and pipe materials on chlorine and chloramine decay and disinfection by-product (DBP) formation. These experiments are being conducted in parallel using both unlined metallic and new polyvinyl chloride (PVC) pipe. The first phase of these experiments (which will be reported here) has focused on the effect of flow rate and pipe materials on the loss of chlorine disinfectant residuals. Results from these studies indicate that there is significant disinfectant wall demand in unlined metallic pipe even under stagnant and laminar flow conditions and that increases in flow rate can increase this demand. Wall demand in the PVC pipe, however, was found to be virtually nonexistent. Studies were also conducted on the rate of trihalomethanes (THM) formation under stagnant, laminar, transitional and turbulent conditions. Planned experiments include studies on chloramines and further attempts to isolate the effects of materials on disinfectant reaction kinetics. It is believed that results from these studies can be used to develop strategies to help maintain adequate disinfectant levels in distribution system networks