ABSTRACT. by Amy Elizabeth Nutter

Transcription

1 ABSTRACT A COMPARATIVE STUDY OF THE DISINFECTION EFFICIENCY OF PERACETIC ACID AND SODIUM HYPOCHLORITE ON SECONDARY EFFLUENT AT THE MILL CREEK TREATMENT PLANT by Amy Elizabeth Nutter For this internship report, I chose a four-month co-op at the Metropolitan Sewer District of Greater Cincinnati (MSDGC). In a bench-scale study, I compared the disinfection efficiency of peracetic acid (PAA) with the Mill Creek Treatment Plant s (MCTP) current disinfectant, sodium hypochlorite (NaOCl). In recent years, disinfection with PAA has gained attention as a chlorine alternative because of the absence of toxic or mutagenic disinfection by-products. The results obtained indicate that PAA and NaOCl have similar disinfection efficiency against the target organisms of Fecal Coliform and Escherichia coli (E. coli). Four parts per million (ppm) with a 10 minute contact time was necessary for both disinfectants to reach permit level inactivation for Fecal Coliform and 5 ppm to inactivate E. coli. It is recommended that doses 2-5 ppm be pilotscale tested at MSDGC s Little Miami Treatment Plant (LMTP) in order to determine the dose and contact time necessary to reach permit level inactivation. It is estimated that a dose of 4 ppm PAA will result in a chemical cost savings of 95% for LMTP. This report describes peracetic acid, relevant laws and regulations, study results and discussion, and future projects.

2 A COMPARATIVE STUDY OF THE DISINFECTION EFFICIENCY OF PERACETIC ACID AND SODIUM HYPOCHLORITE ON SECONDARY EFFLUENT AT THE MILL CREEK TREATMENT PLANT An Internship Report Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Environmental Sciences Institute for the Environment and Sustainability by Amy Elizabeth Nutter Miami University Oxford, Ohio 2016 Major Advisor Dr. Jason Rech Advisor Dr. Vincent Hand Advisor Dr. Sarah Dumyahn

3 Table of Contents Chapter 1: A comparative study of the disinfection efficiency of peracetic acid and sodium hypochlorite on secondary effluent at the Mill Creek Treatment Plant... 1 Introduction... 1 Background... 5 Methods... 8 Results Discussion Chapter 2: Future Projects PAA Pilot Study at Little Miami Treatment Plant Combination PAA and UV Bench Study and Pilot Study at Sycamore Creek Treatment Plant Chapter 3: Reflection on IES Experience References ii

4 List of Tables Table 1. Harmful Disinfection By-Products and Their Health Effects (Oram 2014)... 5 Table 2. Disinfection Doses Applied for Permit Level Fecal Coliform and E. coli (CFU/100 ml) Inactivation iii

5 Table of Figures Figure 1. Location of the Mill Creek Treatment Plant and Outfall 002 into the Ohio River (MCTP 2014)... 2 Figure 2. Mill Creek Treatment Plant wastewater treatment process flow diagram (MCTP 2014) 3 Figure 3. Map of 2015 PeroxyChem's VigorOx WWT II Pilot Study Sites (PeroxyChem 2015b) 6 Figure 4. Sampling Method Flow Diagram... 8 Figure 5. Experimental Setup of the Membrane Filter Technique for Members of the Coliform Group Figure 6. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Sodium Hypochlorite. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 7. Mill Creek Treatment Plant Secondary Effluent Average E. coli (CFU/100 ml) Inactivation with Sodium Hypochlorite. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 8. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Peracetic Acid. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 9. Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) Inactivation with Peracetic Acid. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 10. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) at 3 and 4 ppm NaOCl and PAA. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 11. Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) at 4 and 5 ppm NaOCl and PAA. Each data point represents an average of the triplicate sampling results with associated standard deviation bars Figure 12. Mill Creek Treatment Plant Secondary Effluent Average Percent Decrease of PAA Residual after 20 minutes. Each data point represents an average of the triplicate sampling results with associated standard deviation bars iv

6 Figure 13. Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) of Fecal Coliform (CFU/100 ml) to Predict Operating Conditions to Achieve Permit Limits Figure 14. Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) of E. coli (CFU/100 ml) to Predict Operating Conditions to Achieve Permit Limits Figure 15. PeroxyChem's Disinfection Pilot Reactor (PeroxyChem 2014e) v

7 List of Acronyms ANOVA BOD CAA CERCLA CFU CIP cbod COD CSO CWA DBPs DO DPR HSD LMTP MCTP MGD MSDGC NaHSO3 NaOCl NELAP NPDES OEPA PAA RCRA SCTP SDWA SSO THM TSS US US EPA UV WET WWTP One-way Analysis of Variance Biological Oxygen Demand Clean Air Act Comprehensive Environmental Response, Compensation, Liability Act Colony Forming Units Capital Improvement Program Carbonaceous Biochemical Oxygen Demand Chemical Oxygen Demand Combined Sewer Overflow Clean Water Act Disinfection By-Products Dissolved Oxygen Disinfection Pilot Reactor Tukey s Honestly Significant Difference Little Miami Treatment Plant Mill Creek Treatment Plant Million Gallons per Day Metropolitan Sewer District of Greater Cincinnati Sodium Bisulfite Sodium Hypochlorite National Environmental Laboratory Accreditation Program National Pollutant Discharge Elimination System Ohio Environmental Protection Agency Peracetic Acid Resource Conservation and Recovery Act Sycamore Creek Treatment Plant Safe Drinking Water Act Sanitary Sewer Overflow Trihalomethanes Total Suspended Solids United States United States Environmental Protection Agency Ultraviolet Whole Effluent Toxicity Wastewater Treatment Plants vi

8 Acknowledgments I would like to thank my parents, Garry and Laurie Stultz, and my husband, Sam Nutter, for all of their love and support. Also I would like to thank my advisor, Dr. Jason Rech, for his knowledge and commitment to me completing my degree, as well as my committee members, Dr. Sarah Dumyahn and Dr. Vincent Hand, for their input and encouragement. I am grateful to Dr. Achal Garg and everyone at Metropolitan Sewer District of Greater Cincinnati for this great opportunity to work in such a supportive and enjoyable environment. vii

9 Chapter 1: A comparative study of the disinfection efficiency of peracetic acid and sodium hypochlorite on secondary effluent at the Mill Creek Treatment Plant Introduction Internship The Master of Environmental Science (M.En) professional degree program at Miami University s Institute for the Environment and Sustainability is designed to strengthen creative problem-solving skills, interdisciplinary training, teamwork and management, effective communication, and quantitative analysis with the purpose of preparing graduates to become professionals in the environmental and sustainability fields (Institute for the Environment and Sustainability, Miami University 2016). A requirement of the M.En. professional degree is the completion of an internship, practicum, or thesis that is in accordance with the student s professional goals and allows them to incorporate their academic experience. In order to fulfill this requirement, I chose a four-month internship with the Metropolitan Sewer District of Greater Cincinnati (MSDGC). During this internship I was involved in a bench-scale study comparing the disinfection efficiency of peracetic acid (PAA) with MSDGC s current disinfectant of sodium hypochlorite (NaOCl). This study was proposed with the ambition that MSDGC could lead the way in applying an environmentally friendly treatment to Cincinnati s wastewater, while still considering cost efficiency. This report describes PAA, relevant laws and regulations, study results and recommendations, and future MSDGC projects. It also includes my personal assessment of the experience and how this internship will shape my future career. Internship Organization Metropolitan Sewer District of Greater Cincinnati The MSDGC is responsible for the collection and treatment of residential and industrial wastewater in Hamilton County, Ohio as well as small portions of Butler, Clermont, and Warren counties, totaling about 212,000 ratepayers. This is an area of more than 290 square miles, containing over 200,000 separate sewer connections that tie into around 3,000 miles of sanitary and combined sewers (MSDGC 2015). MSDGC operates seven wastewater treatment plants (WWTP), more than 100 pump stations, and two package treatment plants. MSDGC treats about 184 million gallons of wastewater per day (MGD), including the pretreated waste from about 200 industrial users (MSDGC 2015). Prior to 1968, the City of Cincinnati operated an independent municipal sewer district that served city residents and 23 suburban communities. Under state law passed in 1968, MSDGC was formed as a county sewer district (MSDGC 2015). A 50-year agreement was formed between Hamilton County and the city that granted the city the responsibility of operating and managing MSDGC. Hamilton County s role is to approve sewer rates and MSDGC s budget and the Capital Improvement Program (CIP), including design and construction of CIP projects (MSDGC 2015). MSDGC s mission is to be recognized as stewards of the community, 1

10 protecting public health and the environment, and providing sustainable water reclamation and watershed management (MSDGC 2015). The largest plant that MSDGC operates is the Mill Creek Treatment Plant (MCTP), which is a secondary treatment facility with an average design flow of 130 MGD. The MCTP discharges through an outfall into the Ohio River at Ohio River mile (Figure 1) (MCTP 2014). When the Ohio River stage reaches 41 feet, the plant effluent is discharged into the Mill Creek. The Ohio River and the Mill Creek are both designated as warmwater habitat, public, agricultural, and industrial water supply, and bathing waters and recreation according Figure 1. Location of the Mill Creek Treatment Plant and Outfall 002 into the Ohio River (MCTP 2014) to Ohio s Water Quality Standards (MCTP 2014). The MCTP treatment process occurs yearround and includes: coarse screening, grit removal and fine screening, pre-aeration, primary settling, conventional activated sludge aeration, secondary clarification, and chlorination with sodium hypochlorite (NaOCl). The treated effluent then discharges to the Mill Creek or Ohio River (Figure 2) (MCTP 2014). 2

11 Figure 2. Mill Creek Treatment Plant wastewater treatment process flow diagram (MCTP 2014) MSDGC s MCTP Wet Chemistry/Plant Lab participates in the National Environmental Laboratory Accreditation Program (NELAP) at a level 3 wastewater analysis. This accreditation program is targeted at environmental laboratories and can encompass all of the EPA regulatory 3

12 programs or as few as one (The NELAC Institute 2015). Comprehensive programs include all types of analyses comprising hazardous waste, wastewater, drinking water, air, and soil under the five EPA regulatory programs of the Clean Air Act (CAA), Comprehensive Environmental Response, Compensation, Liability Act (CERCLA), Clean Water Act (CWA), Resource Conservation and Recovery Act (RCRA), and the Safe Drinking Water Act (SDWA) (The NELAC Institute 2015). Environmental Laws Clean Water Act and National Pollutant Discharge Elimination System permit The CWA was established in 1972 as an expansion of the Federal Water Pollution Control Act in order to provide the structure for regulating pollution discharged into waters of the United States (US) and regulate water quality standards (US EPA 2015). The CWA placed responsibility on the United States Environmental Protection Agency (US EPA) to implement pollution control programs including creating wastewater standards for industry and water quality standards for contaminants in surface waters. The US EPA s National Pollutant Discharge Elimination System (NPDES) permit program regulates the discharge of point source pollutants in surface waters (US EPA 2015 and US EPA 2016). The permit stems from the general requirements of the CWA and limits what can be discharged. It also requires monitoring and reporting and contains other provisions to ensure that the discharge does not harm water quality or public health (US EPA 2015 and US EPA 2016). Industry, municipalities, and other facilities obtain NPDES permits for their point sources, such as pipes or ditches, which discharge directly into surface waters. Each of MSDGC s seven WWTP has its own NPDES permit, in which compliance is monitored by the Ohio Environmental Protection Agency (OEPA). Of all of MSDGC s WWTP, MCTP has the most industrial users. MSDGC implements an approved industrial pretreatment program meaning that industries work with MSDGC compliance monitors to create treatment limits for their effluent before it comes to any of MSDGC s WWTP (MCTP 2014). According to the 2013 NPDES renewal application MCTP has 42 categorical industrial users, 21 significant noncategorical industrial users and 73 other industrial users which discharge approximately MGD (MCTP 2014). OEPA also conducts inspections of MSDGC s combined sewer overflow (CSO) system and sanitary sewer overflow (SSO) system. The CSO system encompasses nearly 40% of MSDGC s sewer system. This CSO system provides relief to the rest of the system during heavy rain events by preventing street flooding and sewage backups into buildings. This allows overflow to go directly into local streams and the Ohio River through outfall structures. Because of the known environmental impacts this untreated sewage can have on aquatic life, wastewater from the CSO and SSO systems is now treated before proceeding into local streams and the Ohio River (MSDGC 2015). 4

13 Background The process of wastewater effluent disinfection ensures the inactivation of disease-causing organisms such as bacteria, viruses, and parasites with the goal of protecting public health and the environment (Lazarova et al. 1998). In the United States, effluents are mainly disinfected by chlorine because of its strong biocide capability. However, research has identified that effluent chlorination can promote the formation of toxic, mutagenic, and carcinogenic disinfection byproducts (DBPs), thus increasing the toxicity of the receiving water (Dell Erba et al. 2007, Kauppinen et al. 2012, Table 1. Harmful Disinfection By-Products and Their Health Effects (Oram 2014) Veschetti et al. 2003). The harmful DBPs and their health effects are listed in Table 1. In a study by Pignati et al. (2011), disinfection of effluents with NaOCl increased the toxicity of the effluent after its discharge into a water body. It was determined that the increase in toxicity was due to the concentrations of the DBPs. Once the DBPs are formed, dechlorination will not remove them (PeroxyChem 2014a). In parts of Europe and Canada, chlorine is not used to disinfect effluents because of its potential to form DBPs (US EPA 2013). Instead, these countries use peracetic acid (PAA). PAA is a strong disinfectant with a broad spectrum of antimicrobial activity. A variety of industries have used PAA for its bactericidal, viricidal, fungicidal, and sporicidal capabilities. In recent years, PAA has gained attention as a possible alternative to chlorine-based wastewater disinfection for several reasons including: (1) the absence of toxic or mutagenic residuals or DBPs, (2) its ease of implementation, (3) broad spectrum of antimicrobial activity, (4) no quenching requirement, (5) small dependence on ph, (6) short contact time, and (7) effectiveness for both primary and secondary effluents (Kitis 2004). Recently approved by the US EPA for wastewater effluent disinfection, VigorOx WWT II is a PAA source produced by PeroxyChem and is a clear, colorless liquid available at a concentration of 12 to 15% (Kitis 2004, PeroxyChem 2014d, US EPA 2012). PAA is an equilibrium mixture of acetic acid (16%) and hydrogen peroxide (23%) and water (45%): CH3COOH + H2O2 CH3COOOH + H2O Acetic Acid Hydrogen Peroxide Peracetic Acid Water 5

14 Stabilizers (<1%) prevent degradation in storage, which allows less than 1% decrease in activity per year (US EPA 2012). The effectiveness of PAA disinfection depends on the characteristics of the wastewater, the dose, and contact time (US EPA 2012). Therefore, the US EPA has allowed each WWTP to determine secondary effluent PAA dose based on the target organisms, water quality, and level of inactivation required (PeroxyChem 2014d, US EPA 2012). Figure 3 is a map of PeroxyChem s recent pilot study sites throughout the US. Compared to disinfection with chlorine, PAA does not form harmful DBPs after reacting with effluent (US EPA 2012). Veschetti et al. (2003) found that PAA and NaOCl have similar antimicrobial activity against Total Coliforms, Fecal Coliforms, Escherichia coli (E. coli), Salmonella sp., and Pseudomonas sp. However, the effluent treated with NaOCl in the Figure 3. Map of 2015 PeroxyChem's VigorOx WWT II Pilot Study Sites (PeroxyChem 2015b) 6 same conditions as PAA gave rise to the formation of harmful DBPs. There are two major criticisms associated with PAA disinfection: (1) increased organic content in the effluent, due to acetic acid, creates the potential for microbial regrowth and (2) high cost (Kitis 2004). Antonelli et al. (2013) observed no significant regrowth of microorganisms, confirming the irreparability of cells damaged by PAA. Complete disinfection is obtained within the first five hours of higher PAA doses, with PAA completely decomposed within 10 hours (Antonelli et al. 2013). Furthermore, in a pilot study in St. Augustine, Florida, Keogh and Tran (2011) found PAA to be 10% less expensive compared to the chlorination/de-chlorination system because PAA was more efficient, reaching required inactivation levels at lower doses than chlorine. Dancey (2008) confirmed that at the average dose of PAA, the cost is comparable to NaOCl and as more utilities begin to use PAA, the price will reduce. This is especially true for chlorination/de-chlorination systems in the winter months. The breakdown of organic waste, which occurs from the addition of activated sludge and aeration in the treatment process, produces large amounts of ammonia. Nitrification is a naturally occurring process performed by specialized bacteria in the activated sludge that convert ammonia to nitrites and then nitrates (Jacob and Cordaro 2000). Nitrification is temperature sensitive and the optimum temperature for nitrification is 30ºC or 86ºF (ECOS 2016). When temperatures drop, nitrification occurs less and ammonia is not converted to nitrate. This leaves increased levels of ammonia in the effluent which act as an interfering compound that NaOCl

15 reacts with quickly, exerting a chlorine demand and reducing the efficiency disinfection (NY DEC, US EPA 1999a, ECOS 2016). When PAA decomposes, its by-products are acetic acid, hydrogen peroxide, oxygen, and water. This decomposition occurs in two phases: (1) an initial decrease, followed by (2) a slow decomposition (PeroxyChem 2015a). The initial decrease is due to an oxidant demand, caused by reactions with transition metals, suspended and dissolved solids, and organic species within the water (PeroxyChem 2015a). These are three possible ways in which PAA decomposes: (1) spontaneous decomposition, (2) hydrolysis, 2 CH3CO3H 2 CH3COOH + O2 CH3CO3H +H2O CH3COOH + H2O2 and (3) transition-metal catalyzed decomposition 2 CH3CO3H + M + 2 CH3COOH + O2 + other products (Kitis 2004, PeroxyChem 2015a). PAA and hydrogen peroxide can be rapidly consumed by any of these reactions if they are at a neutral ph. Hydrogen peroxide decomposes to water and oxygen: 2 H2O2 2 H2O +O2 PeroxyChem (2015a) evaluated the decomposition of PAA and hydrogen peroxide from 15 WWTP across the US. Hydrogen peroxide decomposed and there was no observable accumulation of it in the wastewater. In the PAA equilibrium mixture hydrogen peroxide does not provide anti-microbial aid, but it does provide two benefits to the disinfection efficiency: (1) it acts as a sink for the oxidant demand within the wastewater, resulting in hydrolysis (Equation 2) to be a slower process than spontaneous (Equation 1) or metal-catalyzed decomposition (Equation 3), and (2) it provides a source of dissolved oxygen (DO), which can reduce biological oxygen demand (BOD) related to acetic acid (PeroxyChem 2015a). Studies have shown that PAA produces little to no toxic or mutagenic DBPs when tested in effluents or surface waters (Kitis 2004). Monarca et al. (2001) found that by-products isolated from river waters treated with PAA were mostly carboxylic acids, which are not mutagenic (Kitis 2004). As the effluent is mixed with receiving waters, the addition of increased chemical oxygen demand (COD), BOD, and total suspended solids (TSS) increases the rate of PAA degradation, reducing its impact on aquatic life (PeroxyChem 2014b). The purpose of this research is to compare PAA and NaOCl as disinfectants of secondary effluent at the MCTP in Cincinnati, Ohio. A bench-scale experiment with target microorganisms of Fecal Coliform and E. coli was carried out with the following goals: (1) evaluate the 7

16 suitability of PAA as a wastewater disinfectant in terms of inactivation efficiency of target microorganisms, (2) determine the dose and contact time necessary for permit level inactivation, (3) assess residual PAA, and (4) compare the inactivation efficiency of PAA with NaOCl, the disinfectant currently used at the MCTP. Methods Bench Study Experimental Set-Up The disinfection efficiency of PAA and NaOCl was compared in this bench study that utilized grab samples of secondary effluent from MCTP during the months of September to December The sampling method flow diagram is shown in Figure 4. Secondary effluent from MCTP was treated with NaOCl or PAA as it was tested in parallel. The PAA used was the VigorOx WWT II from PeroxyChem and the NaOCl used was reagent grade 15% solution that was provided by MCTP. The number of grab samples collected each day varied, but were collected in sterile 100 milliliter (ml) plastic bottles at the secondary effluent channel just before the chlorination process and tested within 8 hours of collection. Sampling operations were repeated in triplicate to determine the reproducibility of the obtained results. The disinfectant dosages range from 2-7 parts per million (ppm) on average and contact times observed were 10, 15, and 20 minutes with target microorganisms of Fecal Coliform and E. coli. The samples were analyzed without being diluted (no dilution), and also in 1:10 and 1:100 dilutions. The membrane filter technique was performed for members of the coliform group 9222, which is the adopted technique approved by MSDGC and US EPA (Hall et al. 8 Figure 4. Sampling Method Flow Diagram

17 2006). Figure 5 shows the experimental setup of the membrane filter technique. The standard method plate count measured the Fecal Coliform, as blue colonies after incubation for 24 ± 2 hours in a 44.5 ± 0.2ºC water bath with the desired range of colony forming units (CFU) per 100 ml (CFU/100 ml) per plate. E. coli had a desired range of CFU/100 ml per plate as blue colonies, incubating for the same time in a 35 ± 0.5ºC water bath. PAA dose at zero minutes and residual at 20 minutes were measured by a Peracetic Acid Single Analyte Meter manufactured by CHEMetrics. This PAA test kit treats the sample with an excess of potassium iodide, which the PAA then oxidizes the iodide to Figure 5. Experimental Setup of the Membrane Filter Technique for Members of the Coliform Group 9222 iodine. Iodine then oxidizes N,N-diethyl-p-phenylenediamine (DPD) to form a pink color that is a direct proportion to the PAA concentration (CHEMetrics 2013). MCTP has a NPDES permit level of inactivation required for Fecal Coliform set at a monthly average of 200 CFU/100 ml and a daily maximum of 400 CFU/100 ml for the summer. A monthly average of 1000 CFU/100 ml and a daily maximum of 2000 CFU/100 ml are set in the winter due to lack of Ohio River recreation. MCTP currently does not have a permit for E. coli, but other treatment plants operated by MSDGC do. The permit requires a monthly average of 126 CFU/100 ml and a 284 CFU/100 ml daily maximum. MSDGC s treatment plants do not have a winter permit level for E. coli, but the OEPA will be enforcing E. coli permit limits for all of MSDGC s treatment plants within the next decade. Statistical Analysis Statistical Analysis was performed in R and Microsoft Excel The analysis performed were Shapiro-Wilk normality tests, Dunnett s tests for comparing all treatments with a control, Tukey s Honestly Significant Difference (HSD) tests, and One-way Analysis of Variance (ANOVA) to test the two hypotheses: (1) H0 = µcontrol = µ2 ppm, µ3 ppm, µ4 ppm, µ5 ppm, µ6 ppm, and µ7 ppm H1 = the control mean is different from the treatment group means α = 0.05 (2) H0 = µ2 ppm = µ3 ppm = µ4 ppm = µ5 ppm = µ6 ppm = µ7 ppm H1 = two or more means are different from the other means α =

18 µ0 representing the mean of the control group and µ# representing the means of the concentrations of the disinfectants. The Tukey s HSD tests were performed on all treatment doses because this analysis tests the differences in the means as if they were all separate and gives a more accurate comparison of all the means. Because of the number of dosed treatment groups and the number of comparisons made, Tukey s HSD was chosen. Dunnett s test for comparing all treatments with a control was completed on all of the treatment groups to explore the important comparison between the control treatment and the six dosed treatments. Finally, the One-way ANOVA test was used to compare the means of two or more treatment groups because there was only one factor, disinfectants effect on the wastewater. Results For this study, doses and contact times were designed to identify the disinfection rates and doses necessary to meet the NPDES permit limit of Fecal Coliform at 200 CFU/100 ml and the acceptable EPA limit for E. coli at 126 CFU/100 ml with the overall goal of providing a cost effective and environmentally friendly alternative for disinfections at MSDGC. Disinfection efficiency There was a dose and time dependent response observed in this study. On average, the low end of initial microbial concentrations was 7762 CFU/100 ml and the high end of initial microbial concentrations was 202,333 CFU/100 ml. The PAA and NaOCl disinfection displayed a log reduction from about 1 to 4.5 of Fecal Coliform and E. coli depending on the initial bacterial concentration, residual PAA, and contact time. Therefore, the disinfection trend on initial microbial concentrations was as the dose and contact time increased, so did the disinfection efficiency of either PAA or NaOCl on the target microorganisms. Shapiro-wilk normality tests were performed on all of the treatment doses and showed that the data are normally distributed with p-values <0.05. Using the Dunnett s test and Tukey s HSD tests the treatment groups were compared to the control for that treatment group. For effluent treated with NaOCl and tested for Fecal Coliform, treatment groups 2 ppm, 3 ppm, and 4 ppm were all found to be significantly different from the control group with p-value <0.001, and the 5 ppm treatment group had a p-value of <0.1. The treatment group of 6 ppm did have a One-way ANOVA p-value of <0.1, which shows that there is a significant difference in that treatment groups data. When the treatment groups were compared with each other, the 3 ppm treatment group at a 10 minute contact time was significantly different than the other treatment groups, except for 2 ppm. Figure 6 displays that this could be because 3 ppm was the only treatment group at the 10 minute contact time not to be under the permit limit of 200 CFU/100 ml. 10

19 Average Fecal Coliform Colonies (CFU/100mL) Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Sodium Hypochlorite Contact Time (minutes) 2 ppm 3 ppm 4 ppm 5 ppm 6 ppm 7 ppm Permit Limit Figure 6. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Sodium Hypochlorite. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. For effluent treated with NaOCl and tested for E. coli, the treatment groups of 2 ppm, 3 ppm, 4 ppm, and 5 ppm all were significantly different that that treatment groups control with p-values <0.01. The 6 ppm treatment group did have a One-way ANOVA p-value of <0.1, which shows that there is a significant difference in that treatment groups data. When the treatment groups were compared with each other, the 3 ppm treatment group at a 10 minute contact time was significantly different than the other treatment groups, and the 3 ppm treatment group at any contact time was significantly different than the 2 ppm at 10 minutes. This could be because 2 ppm at 10 minutes and all of the 3 ppm treatment groups were the only treatment groups not to be under the permit limit of 200 CFU/100 Ml (Figure 7). 11

20 Average E. coli Colonies (CFU/100mL) Mill Creek Treatment Plant Secondary Effluent Average E. coli (CFU/100 ml) Inactivation with Sodium Hypochlorite Contact Time (minutes) 2 ppm 3ppm 4 ppm 5 ppm 6 ppm 7 ppm Permit Limit Figure 7. Mill Creek Treatment Plant Secondary Effluent Average E. coli (CFU/100 ml) Inactivation with Sodium Hypochlorite. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. For effluent treated with PAA and tested for Fecal Coliform, treatment groups 2 ppm, 3 ppm, and 4 ppm had a Dunnett s test and Tukey s HSD p-value of <0.05 and the 5 ppm treatment group had a p-value of <0.1. Treatment groups 2 ppm, 3 ppm, 4 ppm, and 5 ppm had One-way ANOVA p-values of <0.05 and 6 ppm was <0.1, confirming that these treatment groups were significantly different from the control group for that treatment. The 2 ppm treatment group at all contact times was significantly different than any other treatment group at all contact times with a p-value <0.01. Figure 8 displays that this could be because the 2 ppm treatment group was the only treatment not to make it below the permit limit of 200 CFU/100 ml. 12

21 Average Fecal Coliform Colonies (CFU/100mL) Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Peracetic Acid Contact Time (minutes) 2 ppm 3 ppm 4 ppm 5 ppm 6 ppm 7 ppm Permit Limit Figure 8. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) Inactivation with Peracetic Acid. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. For effluent treated with PAA and tested for E. coli, treatment groups 2 ppm, 3 ppm, and 4 ppm had a Dunnett s test and Tukey s HSD p-value of <0.001 and the same treatment groups including 5 ppm had One-way ANOVA p-values of <0.05. This confirms that treatment groups 2 ppm through 5 ppm were significantly different than the control group for that treatment. The 2 ppm treatment group at the 15 minute contact time was the only treatment group to be significantly different from the rest of the treatment groups at any contact time with a p-value of <0.01. As Figure 9 shows, this is because the 2 ppm treatment group at the 15 minute contact time is the furthest data point from the permit limit. 13

22 Average E. coli Colonies (CFU/100mL) Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) Inactivation with Peracetic Acid Contact Time (minutes) 2 ppm 3ppm 4 ppm 5 ppm 6 ppm 7 ppm Permit Limit Figure 9. Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) Inactivation with Peracetic Acid. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. At the 10 minute contact time, in order to achieve permit level inactivation for Fecal Coliform and E. coli, a dose of 4 ppm and 5 ppm of PAA and NaOCl, respectively, was necessary. For Fecal Coliform, at a 15 or 20 minute contact time, permit level inactivation could be attained at 3 ppm for both PAA and NaOCl (Figure 10). For E. coli, at a 20 minute contact time, permit level inactivation could be attained at 4 ppm for both disinfectants (Figure 11). Table 2 contains average colony counts for each dose and disinfectant for a different perspective on the data. 14

23 Average E. coli Coliform (CFU/100 ml) Average Fecal Coliform (CFU/100 ml) Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) at 3 and 4 ppm NaOCl and PAA NaOCl 3 ppm NaOCl 4 ppm PAA 3 ppm PAA 4 ppm Permit Limit Contact Time (minutes) Figure 10. Mill Creek Treatment Plant Secondary Effluent Average Fecal Coliform (CFU/100 ml) at 3 and 4 ppm NaOCl and PAA. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) at 4 and 5 ppm NaOCl and PAA NaOCl 4 ppm NaOCl 5 ppm PAA 4 ppm PAA 5 ppm Permit Limit Contact Time (minutes) Figure 11. Mill Creek Treatment Plant Secondary Effluent Average E. coli Coliform (CFU/100 ml) at 4 and 5 ppm NaOCl and PAA. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. 15

24 Table 2. Disinfection Doses Applied for Permit Level Fecal Coliform and E. coli (CFU/100 ml) Inactivation PAA residual Residual PAA was measured after a 20 minute contact time with samples in the treatment groups 2 ppm, 3 ppm, 4 ppm, and 5 ppm. The treatment groups 6 ppm and 7 ppm could not be measured because the Peracetic Acid SAM is not able to read more than 5.0 ppm PAA. As shown in Figure 12, residual amounts of PAA decreased approximately 20-30% after 20 minutes. These percent decreases are based on an average of two sampling days for each treatment group. PAA decomposition is dependent on the wastewater, so as the wastewater changes, so will the decomposition of PAA. 16

25 Average Percent Decrease 35.0 Mill Creek Treatment Plant Secondary Effluent Average Percent Decrease of PAA Residual after 20 minutes Dose (parts per million) Figure 12. Mill Creek Treatment Plant Secondary Effluent Average Percent Decrease of PAA Residual after 20 minutes. Each data point represents an average of the triplicate sampling results with associated standard deviation bars. Predicting an Operating Conditions to Achieve Permit Limits Data from this study were also incorporated into a Ct (C being the dose in mg/l and t being contact time in minutes) value graph, where the dose is multiplied by the contact time in order to predict operating conditions to achieve permit limits (Figures 13 and 14). For example, Fecal Coliform needed 3 ppm of PAA and NaOCl with a 20 minutes contact time in order to achieve permit level inactivation, causing a cluster of Ct values right at the 60 Ct value in Figure

26 E. coli Coliform (CFU/100 ml) Fecal Coliform (CFU/100 ml) 600 Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) Fecal Coliform (CFU/100 ml) PAA Fecal Colonies NaOCl Fecal Colonies Permit Limit Ct (Dose (mg/l)xcontact Time (minutes)) Figure 13. Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) of Fecal Coliform (CFU/100 ml) to Predict Operating Conditions to Achieve Permit Limits Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) E. coli Coliform (CFU/100 ml) PAA E. coli Colonies NaOCl E. coli Colonies Permit Limit Ct (Dose (mg/l)xcontact Time (minutes)) Figure 14. Mill Creek Treatment Plant Secondary Effluent Dose Multiplied By Contact Time (Ct) of E. coli (CFU/100 ml) to Predict Operating Conditions to Achieve Permit Limits 18

27 Discussion Due to the significant difference between the control group and the dosed treatment groups the first null hypothesis is rejected and the alternative hypothesis is accepted. The second null hypothesis is also rejected due to the significant difference within the treatment groups and the alternative hypothesis is accepted because two or more means are different from each other. Disinfection Efficiency Secondary effluent disinfection efficiency with PAA and NaOCl was tested and evaluated through a bench-scale study. The results obtained in this study indicate that PAA and NaOCl have similar disinfection efficiency against target organisms. At the 10 minute contact time, both PAA and NaOCl needed 4 ppm and 5 ppm to achieve permit level inactivation of Fecal Coliform and E. coli, respectively. For Fecal Coliform, at a 15 or 20 minute contact time, permit level inactivation could be attained at 3 ppm for both PAA and NaOCl. For E. coli, at a 20 minute contact time, permit level inactivation could be attained at 4 ppm for both disinfectants. Data evaluated in this bench study have indicated that a dose range of 2-5 ppm should be the recommended dose for a pilot-scale study. This pilot study will be beneficial to MSDGC for many reasons. The more data that are collected will help MSDGC to decide whether to use PAA and PeroxyChem with a plant-scale study to determine energy and cost efficiency. Cost Efficiency The suitability of PAA as chlorine alternative for wastewater disinfection has been proven to be practical and economical for many WWTP in the US. The results show that PAA disinfection could ultimately become an affordable and valuable process for MSDGC s treatment plants. The Little Miami Treatment Plant (LMTP), one of MSDGC s seven WWTP, dechlorinates its effluent before being discharged into the Little Miami River. According to MSDGC s electronic operations system, eops, in 2015 LMTP treated an average of 29 MGD and spent $6,720,255 on NaOCl and sodium bisulfate (NaHSO3). A dose of 4 ppm PAA treating an average of 29 MGD would cost $298,062 per year (Beck and Clark 2015). This would be a 95% cost savings if LMTP were to switch to PAA. PAA is able to comply with permits and regulations and is becoming competitively priced as more WWTP in the US start utilizing it. For some WWTP, the chlorination/de-chlorination process forms chlorinated DBPs. PAA is a cost effective alternative for wastewater utilities to replace the chlorination process as a means to eliminate the potential to form DBPs because of permit violations and fines. Research performed by PeroxyChem has shown that VigorOx WWT II has demonstrated to be an effective disinfectant, as well as cost efficient, for WWTP since PAA does not form harmful DBPs and eradicates concerns with compliance issues (PeroxyChem 2014a). Another reason PAA could ultimately be cost effective for any of MSDGC s WWTP is the interfering effect that ammonia has with NaOCl that exerts a chlorine demand and reduces 19

28 disinfection efficiency. Therefore it would be more cost effective to release a steady dose of 4 ppm PAA than it would be to keep increasing the dose of NaOCl to ensure microorganism inactivation. Furthermore, due to the amount of mixing in the treatment process, a pilot study or plant study, could find that a lower dose of PAA will be necessary for permit level inactivation. In conclusion, further studies, including pilot and plant studies, need to be performed in order to gather further data to determine specific dose requirements of PAA for MSDGC s WWTP and analyze whether it will be cost effective enough to make the transition from NaOCl to PAA. 20

29 Chapter 2: Future Projects PAA Pilot Study at Little Miami Treatment Plant The LMTP discharges into the Ohio River at Ohio River mile The LMTP is a secondary treatment facility with an average design flow of 55 MGD. Wet stream processes include: influent pumping, screening and grit removal, primary settling, activated sludge aeration, secondary clarification, chlorination, and dechlorination (Little Miami WWTP 2013). LMTP has a Fecal Coliform discharge limit in the summer of 200 CFU/100 ml monthly average and 400 CFU/100 ml maximum daily and in the winter a 1000 CFU/100 ml monthly average and 2000 CFU/100 ml daily maximum. Within the next few years, LMTP will be given summer discharge limitations for E. coli of 130 CFU/100 ml monthly average and 292 CFU/100 ml daily maximum. These effluent loadings are based on an average design flow of 55 MGD (Ohio EPA 2014). LMTP chlorinates with NaOCl and dechlorinates with NaHSO3. According to the US EPA (2000) dechlorination can be difficult to control when near zero levels of residual chlorine are required. Overdosing can lead to sulfate formation, which suppresses DO content and lowers ph of treated effluent. It also contributes to sodium pollution and increased total dissolved salts in the water body it is discharged into (US EPA 2000). This chlorination/dechlorination process and the potential 95% cost savings has lead MSDGC to choose LMTP as the pilot study location for PeroxyChem s PAA product, VigorOx WWT II. PeroxyChem s Disinfection Pilot Reactor (DPR) (Figure 15) will confirm if PAA can attain compliance with the NPDES permit limits and determine the dose and contact time required to do so. The permit requires Fecal Coliform not to exceed 200 CFU/100 ml in the summer months (April to October). Since the pilot study will start in late April, it is proposed that a pilot study disinfection goal of 100 CFU/100 ml be used as a daily maximum, as well as, a 100 CFU/100 ml daily maximum for E. coli. Figure 15. PeroxyChem's Disinfection Pilot Reactor (PeroxyChem 2014e) The pilot study will be six weeks, which includes 30 days of data collection and analysis. Four doses will be tested during the first 20 days of the trial. Based on these results a dose will be 21

30 selected for the last 10 days of the trial. I will collect samples from the influent, as a control, and at the 8, 15, and 30 minute contact times from different port valves in the DPR. Fecal Coliform, E. coli, PAA Residual, Chloride, ph, and Temperature analyses will be performed twice daily. There could also be a separate PAA Residual study during this pilot study to determine when PAA completely decomposes in LMTP s effluent. DO and Ammonia analyses will be performed once daily. TSS and Carbonaceous Biochemical Oxygen Demand (cbod) analyses will be performed on a weekly basis. Furthermore, Whole Effluent Toxicity (WET) will be tested once during the trial. WET testing will be a 24-hour composite sample for acute toxicity with the target organisms of Ceriodaphnia dubia and Pimephales promelas. If PAA performs as well in the pilot study as it did in the bench study, there is a high probability that MSDGC will move forward with a plant-scale study. Eventually, LMTP could change its NPDES permit to disinfection with PAA. Ohio EPA will also be sampling alongside PeroxyChem and MSDGC with the purpose of gathering more data to determine if MSDGC and other WWTP in Ohio can make the transition to PAA. Combination PAA and UV Bench Study and Pilot Study at Sycamore Creek Treatment Plant The Sycamore Creek Treatment Plant (SCTP) is operated by MSDGC and discharges into Sycamore Creek at river mile Sycamore Creek then joins the Little Miami River at mile (SCTP 2015). Sycamore Creek is designated for warm-water habitat, agricultural water supply, industrial water supply, and Class B primary contact recreation under Ohio s Water Quality Standards. The plant has an average daily design flow of 9 MGD with a peak flow of 18 MGD. Wet stream processes include: fine screening, grit removal, secondary clarification, tertiary clarification by disc filtration, and Ultraviolet (UV) disinfection (SCTP 2015). An UV disinfection system utilizes electromagnetic energy from a mercury arc lamp to penetrate the cell wall of an organism and destroy its DNA and RNA, preventing the cell to reproduce. The characteristics of the wastewater, the intensity of the UV lamp, and exposure time determine the effectiveness of the UV disinfection system (USEPA 1999b). UV radiation from mercury arc lamps can either be low or medium pressure with low or high intensity settings. The optimum wavelength range of 250 to 270 nanometers (nm) is used to effectively inactivate microorganisms. Generally, medium-pressure lamps are used in large WWTP and have a greater inactivation rate than low-pressure lamps because of their higher intensity (USEPA 1999b). Studies performed by Caretti and Lubello (2003), Rajala-Mustonen (1997), and Beber de Souza et al. (2015) have all concluded that a combination of PAA and UV disinfection treatment has a much higher inactivation for microorganisms than just PAA or UV radiation alone. The introduction of PAA before the UV radiation has been found to be significantly more effective compared to when PAA is introduced after UV radiation. This synergistic effect allows PAA to damage the microorganism s cell wall allowing the UV radiation to completely destroy RNA and DNA and restrict the cell s regeneration ability (Caretti and Lubello 2003, Beber de Souza et al. 2015, Rajala-Mustonen 1997). As an added benefit, this process minimizes the formation of 22

31 DBPs and allows for the use of lower doses of PAA and UV radiation, resulting in cost efficiency (Beber de Souza et al. 2015). I have already performed preliminary bench studies, but the combination disinfection treatment of PAA and UV radiation needs to be investigated further. Its high inactivation efficiency of target microorganisms at lower doses, has the potential to save energy and provide cost efficiency. The already existing UV disinfection system and short contact time conduit at SCTP will be the ideal location for the PAA and UV pilot study. Once bench studies on SCTP tertiary effluent are complete, a pilot study will be discussed. SCTP has a summer discharge limit for E. coli at 126 CFU/100 ml monthly average and a 284 CFU/100 ml daily maximum. Therefore, the bench and pilot study disinfection goal of 100 CFU/100 ml for Fecal Coliform and E. coli will be set. 23

32 Chapter 3: Reflection on IES Experience During my IES experience I have sharpened my problem solving and critical thinking skills. I have also made connections with people in different fields of the environmental industry through the symposium, guest speakers, and field trips that I would have not met without this guidance of this program. The basic networking skills, LinkedIn training, and resume and cover letter building workshops have also been a huge help in my job search. Sharpening my problem solving and critical thinking skills has best prepared me for this internship with MSDGC. The classes with labs and classes in fields I have never taken before, including Wetlands Assessment and Regulations, Environmental Law, Paleoclimatology, Limnology, and Environmental Protocols, were especially academically challenging, and have helped me and continue to help me long term with any future career in the environmental field. Also the classes in statistics, and learning how to write code with R, have been a tremendous help in the completion of this report. I have enjoyed my experience working for the City of Cincinnati. This internship with MSDGC has really changed my perspective on working in the lab. I especially enjoy research and development projects now and I hope to continue them in the future, whether it be with MSDGC or another entity. 24

33 References Beber de Souza, J, F.Q. Valdez, R.F. Jeranoski, C. Mango de Sousa Vidal, and G.S. Cavallini. Water and Wastewater disinfection with peracetic acid and UV radiation using advanced oxidative process PAA/UV. International Journal of Photoenergy. December 28, : 1-7. Beck, J. and B. Clark. Testing of Peracetic Acid and Hypochlorite for Wet Weather Disinfection Ohio Water Environment Association Technical Conference and Exhibition. Accessed April 12, Hypo_Wet_Weather_Disinfection.pdf Caretti, C. and C. Lubello. Wastewater disinfection with PAA and UV combined treatment: a pilot plant study. December 20, Water Research 37: CHEMetrics. Technical Data Sheet Version 2, June Accessed March 30, Dell Erba, Adele, Dario Falsanisi, Lorenzo Liberti, Michele Notarnicola, Domenico Santoro. Disinfection by-products formation during wastewater disinfection with peracetic acid. Desalination 215 (2007): ECOS Environmental Consultants Wastewater Nitrification: How it works. Accessed January 11, Hall, Nancy, Paul Berger, John K. Brokaw, Terry C. Covert, Sharon H. Kluender, Mark W. LeChevallier Membrane filter technique for members of the coliform group. Standard Methods Committee Accessed November 25, Institute for the Environment and Sustainability, Miami University. Master of Environmental Science (M.En.) Degree Accessed February 3, Jacob, K. and E. Cordaro. Nitrification. Rensselaer Polytechnic Institute, Accessed April 13, Kauppinen, Ari, Jenni Ikonen, Anna Pursianinen, Tarja Pitkänen, and Ilkka T. Miettinen. Decontamination of a drinking water pipeline system contaminated with adenovirus and Escherichia coli utilizing peracetic acid and chlorine. Journal of Water and Health 10 (2012): Kitis, Mehmet. Disinfection of wastewater with peracetic acid: a review. Environment International 30 (2004):