Maher, Chris

Chris Maher is a Senior Operations Analyst in the Technology Development and Research Department at Clean Water Services in Washington County, Oregon. He has a BS in Chemistry from Colorado State University, and after a stint as a recreational hydrologist, began his career in operations at the Upper Blue Sanitation District in Breckenridge, CO. While there he earned his MS degree in Environmental Engineering through the Illinois Institute of Technology under the auspices of the Water Research Foundation. He is an Oregon Grade IV certified wastewater operator.

Titles from this speaker

Commissioning of a Modern Centrifuge Solids Dewatering System

Abstract

Introduction Clean Water Services (CWS) is a public utility providing wastewater, stormwater, and watershed management to the residents of Washington County, Oregon, USA. Among the utility's facilities is the Rock Creek Advanced Water Resource Reclamation Facility (WRRF), a 45 MGD (dry weather) campus that manages the solids stream through mesophilic anaerobic digestion, centrifuge dewatering, and land application of Class B biosolids. CWS has recently completed the design, construction, and commissioning of a modern dewatering system at the Rock Creek AWRRF. Project Overview The existing dewatering equipment consisted of a single Humbolt Bird centrifuge dating to 1990. The size of the machine dictated 24/7 operation to keep up with solids production. Redundancy was provided by keeping a spare rotating assembly (bowl and scroll) on site, and maintenance staff were able to effect a complete change out in the course of an 8-hour workday. The original emulsion polymer make down system was comprised of a Dynablend unit, aging tank with mixer, transfer pumps, a 5,000 gallon feed tank, and 3 dosing pumps. After failure of the Dynablend a single static mixer was used for polymer make down. Over time two additional polymer dosing locations were added upstream of the original location at the centrifuge. Before installation of the Humbolt Bird centrifuge, solids dewatering was done with 4 belt filter presses which were still on site. The project began with removal of the four belt filter presses to make space for the installation of two GEA Watermaster CF 8000 centrifuges. The solids processing building was retrofitted for seismic resiliency as part of a 50-year earthquake preparedness plan. The polymer system was entirely rebuilt, requiring a temporary system using polymer totes. The existing flat bottom bulk polymer tanks were replaced with conical bottom tanks with transfer/recirculation pumps. Three Velodyne VeloBlend VM-P polymer make down units were installed to serve both thickening and dewatering applications and the mixed aging tanks were removed. The ability to use the 5,000 gallon feed tank was retained as an option for both maintenance of the polymer system and providing solution aging. Three polymer dosing points were designed with automatic control and flow measurement where the intermediate dosing point included a static mixer on the solids feed line immediately downstream of the dosing point. The system also included instrumentation to measure the feed solids density (%TS) and the centrate TSS (Valmet, Finland). This instrumentation enables real time cost control calculations and automated polymer dosing to maintain centrate quality. The system is shown in Figure 1. Commissioning The mechanical start-up of the system was impressively trouble free. CWS enjoys the benefit of in-house controls, electrical, instrumentation, maintenance and engineering staff and requires two rounds of operational readiness testing (ORT) that provides early identification and remediation of functional issues. The problem encountered is not at all uncommon and was that the system did not immediately meet performance specification. The performance specification called for the system to achieve 95% capture, and 24% TS cake at a maximum polymer dose of 27 lbs active per ton of dry solids. While the capture could be achieved at the limit of the polymer dose, the cake solids could not be met. While this is not unusual for start-up of a new system, the reduction in cake solids from the old to new system was alarming. The old system was consistently achieving cake solids between 22 and 23%, the new system was fluctuating between 20 and 22% (Figure 2). As with any new system, time is needed for optimization. The operations staff was familiar with dewatering optimization procedures having been trained to tune the process to lowest total cost and began learning the new system. The primary question to answer was in the polymer system. To ensure that the system was utilizing fully activated polymer in the most efficient way possible, a matrix was developed to systematically adjust one polymer variable at a time and analyze performance. Additionally, a static mixer was installed downstream of one VeloBlend to see if there was a difference in more polymer activation energy. The primary variable is the polymer solution concentration and the secondary variables are polymer make up with or without static mixer, injection point, and aging tank. Each condition is run for one day and three sample sets of cake and centrate are analyzed. The matrix becomes complex and time consuming. There are 8 solution concentrations at three dosing points for 24 combinations. Those are tested with and without the static mixer, then with and without aging for a total of 96 conditions. This type of evaluation will not only optimize the process, but find the limit of cake solids at the optimal condition. To date staff have found an optimal solution concentration of 0.24% active over all conditions and insignificant effect of other conditions, except for best results dosing at point 1 which is at the machine. The next test is to rerun the matrix using the aging tank, and adjusting aging times. Summary This abstract, presentation, and manuscript describe a dewatering modernization project incorporating features from the culmination of 10 years of dewatering optimization at CWS. It underscores the pitfalls of performance specifications and guarantees, the time needed for full optimization and elimination of causes of non-performance. By the time of conference the evaluation will be complete and a discussion of resolution of contract, to the degree possible, will be available for inclusion.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerMaher, Chris

Presentation time

09:30:00

10:00:00

Session time

08:30:00

11:15:00

SessionCase Studies & Lessons Learned

Session number27

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicConstruction, Dewatering Optimization, Process Design

Author(s)

Maher, Chris

Author(s)C. Maher1, M. Gates1, D. Clements1, M. Idehara1, P. Sunderland1

Author affiliation(s)Clean Water Services 1; Clean Water Services 1; Clean Water Services 1; Clean Water Services 1; Clean Water Services 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159468

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

Energy and Other Efficiencies Gained from Influent Flow Equalization

Abstract

Introduction Clean Water Services (CWS) is a wastewater, stormwater, and watershed management utility serving the populous of Washington County, Oregon USA through implementation of a watershed based NPDES permit. The Rock Creek AWRRF recovers water resources from an average dry weather flow of 25 MGD wet weather flow of 80 MGD and peak hours of 150 MGD. The resource stream begins the recovery process at the influent pump station (IPS) where it is lifted approximately 65 feet by 7 influent pumps. The influent wet well includes two discharge headers, two flow meters and, in total, five 900 hp pumps and two 450 hp pumps (Figure 1). The idea has long existed at CWS to increase the level setpoint, decreasing the total discharge head on the pumps to gain energy efficiency. In 2018, catalyzed by the WEF/WRF/LIFT Intelligent Water Systems (IWS) Challenge, CWS undertook a 6-week test to increase the level setpoint by 16 feet to measure energy savings and the effects on the conveyance system by leveraging available data. Although successful, the energy savings was doubtfully worth the potential for long term degradation to the collection system. However, without catastrophic failures the door was opened to pursue other ideas. Further data analysis of diurnal flow patterns revealed that up to 70% flow equalization (FEQ) could be achieved on a daily basis. During FEQ control the IPS wet well level varies linearly from 103' to 118' at 10:00 and 01:00 respectively. The first test was performed in the summer of 2020 for a two-week period. Subsequent analysis showed efficiency gains not only at the IPS but in downstream processes. The concept was refined and in 2021 the facility began operating full time in FEQ control. Since then FEQ control has been the default operating mode except during storm events when the wet well level is lowered to standard mode. This has offered CWS the opportunity to examine and attempt to quantify the efficiency gains from FEQ on a whole plant basis. Methods Data analysis was performed on hourly average values extracted from the SCADA historian. Energy savings were calculated from motor and VFD efficiency and pump data, at an average level of 110 feet, and compared over 7 periods of FEQ control and 6 periods of standard control from 2/18/2022-6/9/2022. Equipment runtime was compared in terms of number of hours of lag unit runtime per total hours during either operating mode. It was estimated that the facility would operate in FEQ control 98.3% of the time, returning to standard mode only for wet weather events. This data analysis was done in partnership with Energy Trust of Oregon (ETO), which provided rebates for realized energy savings. Results Energy Efficiency The following plant processes were evaluated for energy savings:

*IPS

*IPS Odor Control

*Primary Effluent Pump Stations (PEPS)

*Blowers

*RAS Pumps

*Tertiary Pump Stations

*Air Compressors Energy savings were realized in the IPS, IPS odor control, PEPS, and RAS pumps. The IPS odor control fan speed is reduced at wet well levels over 105 feet. Influent FEQ transfers downstream to equalize flow in the PEPS and the RAS pumps. Energy savings in these systems were calculated from measured motor speed and equipment data as the difference between FEQ and non-FEQ periods. Total energy savings were estimated at 445,851 kWh/yr. The breakdown of energy savings per system is given in Table 1. Lag Unit Runtime The IPS and PEPS are configured in a lead-lag setup. Reduction in peak flow provided by FEQ reduced the runtime on the lag unit, overnight baseline flows are augmented but did not transfer the run hours to a different time of day. Primary effluent is split between east and west PEPS. Hourly pump speed data were compared between FEQ and non-FEQ periods for hours above 100% pump speed, indicating that a lag unit was running. Lag unit runtimes were reduced in all three pump stations, as shown in Table 2. Controls Stabilization While peak flow attenuation provides for energy and equipment efficiency, augmentation of overnight low flows can keep control systems operating in a more optimal range. One example of this can be found in the bioreactor air flow control valves. The dissolved oxygen (DO) setpoint is maintained through a cascading control loop where the span between the measured and setpoint DO is converted to a change in air flow rate, achieved by modulating an actuated air flow control valve. A control valve can modulate between 15 and 100% through many cycles during the low flow period of the day when FEQ is not used. The modulation is reduced to between 20-30% with FEQ (Figure 2). Current Work CWS is again engaged with ETO on a project to refine FEQ operation to maximize energy savings by creating new FEQ control programs. Power data from the IPS is being leveraged for asset management and initial analysis has found that one of the 450 hp pumps operates at significantly lower efficiency (kW/MGD) than the other. PEPS data has been examined more closely for operational changes that would have the east and west PEPS work more as a singular pump station. Initial analysis estimates are that an additional 500,000 kWh could be saved at the IPS, 100,000kWh at the PEPS, and 700,000 kWh by improving the efficiency of the underperforming PEPS pump. This project is expected to be completed and ready for inclusion at WETFEC 2024.

Clean Water Services has implemented influent flow equalization at the Rock Creek Advanced Water Resource Reclamation Facility using available volume in the conveyance system. Flow equalization achieves an energy savings of approximately 500,000 kWh per year through a combination of reduced specific pumping energy through lower total discharge head on the influent pumps, reduced influent pump station odor control fan demands, and savings in downstream pump stations.

SpeakerMaher, Chris

Presentation time

09:00:00

09:20:00

Session time

08:30:00

10:00:00

SessionEnergy Conservation: From a Want to a Must

Session number305

Session locationRoom 346

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Intermediate Level, Resilience, Safety, and Disaster Planning

Author(s)

Maher, Chris, Schauer, Peter, Lorntson, Erik, Sunderland, Perry

Author(s)C. Maher1, P. Schauer1, E.J. Lorntson1, P. Sunderland2

Author affiliation(s)1Clean Water Services, OR, 2Clean Water Services

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159728

Volume / Issue

Content sourceWEFTEC

Word count10

Evolution of an Intelligent Biosolids System

Abstract

Introduction Clean Water Services (CWS) is a wastewater, stormwater, and watershed management utility serving the populous of Washington County, Oregon through implementation of a watershed based NPDES permit. CWS operates 4 water resource recovery facilities (WRRF), of which two are advanced treatment facilities producing Class B biosolids through mesophilic anaerobic digestion and centrifuge dewatering. Struvite fertilizer is manufactured from thickening and dewatering liquors. The NPDES permit requires phosphorus removal to 0.10 mg/L from May to October, accomplished with a combination of enhanced biological phosphorus removal (EBPR) and chemical phosphorus removal by alum addition in primary and tertiary processes. The ramification in solids processing is that there exists significantly different sludge dewaterability characteristics between the summer and winter months. In the winter of 2014, faced with outlandish polymer doses (~80 lbs. active/dry ton) CWS completed a consultant assisted (The Centrifuge Guy) optimization of the dewatering process that led to a new sensibility in centrifuge operation focused on achieving the lowest total cost for biosolids production. The subsequence of this original optimization has been the development of an intelligent biosolids system that appropriates technology, software, and human resources to achieve total cost efficiency in the biosolids management program, in both materials and labor. Centrifuge Operation Dewatering operators are burdened by triumvirate goals; high cake solids, low centrate or filtrate solids, and polymer dose control. Relationships between the three are not simple and site specific. Maximizing one parameter often leads to sacrificing the others. When the goals are aggregated and presented as the component costs of haul, polymer, and recycled solids and as the total cost, the job becomes clear. Beginning with simple spreadsheet tools, CWS has advanced cost driven centrifuge operation to real-time SCADA displays and trending. A centrifuge replacement project offered the opportunity to add instrumentation to the process to advance real-time analysis to real-time control. Process analyzers (Valmet) were installed on the feed sludge line and cake chute for total solids (TS) and on the centrate drain line for total suspended solids (TSS). Previous iterations of cost calculations relied on daily laboratory data and operator analysis of cake solids by moisture analyzer Technology employed in the new system enabled true real-time information. It has also enabled new control automation modes. In TSS control, the polymer dose is adjusted by the PLC to maintain a centrate TSS setpoint for quality control in the feed to fertilizer manufacturing. Data and Report Automation An immense amount of data must be generated, transformed, analyzed and maintained to meet the requirements in the 40 CFR Part 503 regulations as well as to comply with biosolids management plans required by state agencies. An immensity of human resources can be expended to manage this flow of data. Manual transmission of data between databases is not only time consuming but also increases the odds of erroneous data. CWS has implemented smart technologies and digital solutions to automate much of this data management. A prime example of this is the installation of smart scales used to weigh biosolids trucks. Previously weigh tickets would be collected at the end of the month and hand entered into a spreadsheet on an individual hard drive. Utilizing the smart scale, all the ticket data is automatically imported into a SharePoint site that tracks each load as it happens, including weight, vehicle number, and application site destination. Field reports are provided by the applier as they happen and field completion status is continuously updated. The biosolids annual report required by Oregon DEQ contains 21 sections of information to be filled in and an additional 40 pages of supporting documentation. With all the information now located in Hach WIMS and SharePoint databases, the report is largely auto-populated, requires little manual entry, and a final review. Communication and Visualization Power BI has been deployed extensively for communication to managers and stakeholders, but also for visualization of operational efficiency by process control analysts. These dashboards display information ranging from average monthly cake solids to fuel price history and transactions to financial information like budget to actual expenditures. The value of these dashboards is that they aggregate data from different data generators and make it easily accessible to anyone inside or outside CWS. Ongoing Development Efficiencies are continuing to be found by CWS staff. Integration of GIS software is underway to facilitate field application planning that will minimize the distance and number of times that application equipment must be moved to a new site. GIS systems can also be used as visual interfaces providing an array of data on application sites as well as for customizing application rates down to the detailed level of specific sections of an individual field. CWS is also undertaking the agronomy aspect of land applying biosolids as an in-house function. Although it is a small part of the total cost of biosolids utilization, there is the potential for cutting a high amount of waste from the process. Empowering the biosolids management staff with agronomy education and skills can make it possible for a single individual to make a single site visit and accomplish a suite of tasks; field inspection, soil sampling, meeting with hauling and application operators, and developing the personal relationships with landowners that are vital to the success and future of beneficial reuse of biosolids.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerMaher, Chris

Presentation time

15:45:00

16:15:00

Session time

13:30:00

16:45:00

SessionSession 13: Case Studies

Session number13

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicTroubleshooting & Optimization

Author(s)

C. Maher

Author(s)C. Maher1, M. Gates2, 3, 4,

Author affiliation(s)Clean Water Services1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158861

Volume / Issue

Content sourceResiduals and Biosolids

Word count7

Description: Using the Capillary Suction Time Test as a Tool to Support Operation of the...

Using the Capillary Suction Time Test as a Tool to Support Operation of the Dewatering Process

Abstract

Introduction The capillary suction time (CST) test is an established method of evaluating the dewaterability of stabilized wastewater solids and has been used primarily to evaluate different flocculants, flocculant demand, or to determine the differences in dewaterability between solids generated under differing conditions. Many variables exist in modern dewatering processes which offer opportunities for optimization. Flocculant make down systems are now tunable with regard to mixing energies, make down concentrations can be easily changed, and the system may or may not include an aging or feed tank. Often times there are options to dose flocculant at multiple points in the solids feed ahead of dewatering equipment. Feed solids concentration and rheology can also have an effect and pre-dilution of the feed offers another control point to gain efficiency. Clean Water Services (CWS) (Washington County, Oregon, USA) is undergoing the development of CST testing procedures to evaluate, predict, and recommend full-scale dewatering process optimization strategies. Procedure The CST apparatus itself is a simple device that measures electrical continuity between two sets of contacts. The contacts rest on a piece of filter paper, a conditions solids sample is applied to the center of the filter, and water is drawn out across the paper. A timer is initiated when the water reaches the first set of contacts at radius 1, and stopped when it reaches the second set of contacts at radius 2. The lower the time the more easily water is withdrawn from the solids, and the more dewaterable the sample is considered to be. CWS utilizes an OFITE (Houston, Texas, USA) CST apparatus (Part No. 294-50). Although simple in concept, the CST test requires a well thought out procedure and careful technique to improve the accuracy and repeatability of the results. The manufacturers instruction manual contains procedure recommendations including using a syringe or pipette to transfer the conditioned sample to the sample holder, thoroughly cleaning and drying the sample blocks and electrodes between tests, and repeating a minimum of three times and averaging results. Additional notes state that temperature and solids concentration have significant effect on results, and that 5 repetitions per test are recommended. The consequence of these procedural nuances is that it will take a significant amount of time to evaluate a single solids sample at a single flocculant dose through 3-5 repetitions. Over the course of the time required, two major effects can be seen to skew results. First, when evaluating anaerobically digested solids the initial sample will be at a temperature of approximately 37 C for a mesophilic system. Depending on sample size and ambient lab temperature the sample may cool as much as 10 C over the run of 5 repetitions. Second, the made down flocculant solution, whether prepared in the lab or taken from the full-scale system will be aged up to one hour over the trial run. The goal with any bench test is to duplicate as exactly as possible the full-scale system. The procedure under development at CWS attempts to achieve this in multiple ways. The test is considered to be a field test, meaning that it is performed as close to the dewatering process as possible. The flocculant solution is sampled as close to the dosing point as possible to account for activity changes in the piping run from the make down system to the dosing point. The solution is used in the test as quickly as possible, ideally under 1 minute, and a fresh sample is taken for each test. A 4 L dewatering feed sample minimizes temperature changes. In the test itself a 60 mL syringe is capped and inverted, plunger removed, and a 5 mL sample of solids and corresponding polymer dose are concurrently pipetted into the syringe. The plunger is inserted enough to make a seal, the syringe is placed tip up, the cap loosened and the plunger depressed to a volume of 30-40 mL. The cap is tightened and syringe is shaken 30 times in a back and forth motion to effect flocculation. The cap is removed and the conditioned solids are pressed to the end of the syringe, then displaced into the sample holder. Results Initial results of procedure development and investigation of effect of flocculant solution aging illustrate the inherent variability in the test and increases in CST time from flocculant that has been aged on the lab bench. In Figure 1, a dose curve of CST time is shown for the same solids sample conditioned with the same fresh flocculant and run on side by side CST instruments. Although the curves have the same shape, there is chance variability in the CST at a dose of 14 lb. active/DT. The effect of solution aging can be pronounced as shown in Figure 2. Here, two separate runs are shown where the dose remains at 20 lb. active/DT but the solution has aged on the bench up to 30 minutes. Summary The CST test may prove to be a useful tool to support operational decision making and to evaluate the effect in dewaterability of solids treatment processes. The method is however, sensitive to technique and procedure and the nuances of the analysis as a representative bench test must be considered if the resulting data are to be useful. The future of this work, to be completed by time of manuscript include a full procedure, evaluation of effect of flocculant aging, solids sample temperature, flocculant solution concentration, and dosing point. These data will be accompanied with a correlation to full scale operational performance.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerMaher, Chris

Presentation time

08:30:00

11:15:00

Session time

08:30:00

11:15:00

SessionTroubleshooting & Optimization

Session number26

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicChemical Treatment, Dewatering Optimization, Laboratory Methods And Analysis