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A Practical Approach to Ph Control: Brice Poston 9/1/13 1:57 PM Observations from Different Neutralization System Startups Deleted: S Rob 8/30/13 7:47 PM Robert L

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A Practical Approach to Ph Control: Brice Poston � 9/1/13 1:57 PM Observations from Different Neutralization System Startups Deleted: S Rob � 8/30/13 7:47 PM Robert L Rob ! 8/30/13 7:47 PM Deleted: Ph Brice Poston ! 9/1/13 1:56 PM Deleted: A Case Study Of Rob ! 8/30/13 8:33 PM Deleted: Ten A Practical Approach To pH Control: Brice Poston ! 9/1/13 1:57 PM Observations From Different Neutralization System Startups Deleted: s Rob ! 8/30/13 7:47 PM Robert L. Rebodos, PhD, Samanth E. Dawson, PE Formatted ... [2] E. Matthew Fiss, PhD, PE and Edward C. Fiss, Jr., PE Rob ! 8/30/13 7:48 PM Fiss Environmental Solutions, Inc. Deleted: , Samanth E. Dawson Rob ! 8/30/13 7:47 PM Formatted ... [4] ABSTRACT Rob ! 8/30/13 7:48 PM Deleted: and For many industrial facilities, the only pretreatment of process wastewater necessary prior to discharging Rob ! 8/30/13 7:47 PM to a municipal sewer system is simply pH neutralization. In practice, however, a pH control system can Formatted ... [3] be highly complex. All individual components need to perform effectively at all times. The pH probe, Rob ! 8/30/13 7:47 PM considered the weakest link in a pH control system, is prone to failure and needs to be checked and Formatted ... [5] calibrated regularly. More importantly, the control system should be designed properly to provide efficient neutralization even in extreme conditions. A review of the fundamental pH concept including an overview Rob ! 8/30/13 7:47 PM of unit operations, common problems and system design pitfalls encountered in the field are discussed in Deleted: , Inc., 7251 Pineville-Matthews... Rd, [6] this paper. Results of pH probe testing comparing bulb-type and flat-type pH probes are also presented. Rob ! 8/30/13 11:18 AM Issues observed from start-ups of pH control systems from different design companies over the past year Formatted ... [7] at various industrial facilities are enumerated. Solutions to these problems are provided to avoid costly, Brice Poston ! 9/1/13 5:40 PM and sometimes catastrophic, system failure. Deleted: Abstract Keywords: pH control systems, wastewater neutralization, pH probes Brice Poston ! 9/1/13 5:41 PM Formatted ... [8] Brice Poston ! 9/1/13 9:59 PM INTRODUCTION Formatted ... [9] Brice Poston ! 9/1/13 9:59 PM For many industrial facilities, the only pretreatment of process wastewater necessary prior to discharging Formatted ... [10] to a municipal sewer system is simply neutralization to achieve necessary pH discharge requirement. pH, Rob ! 8/30/13 5:21 PM which is generally use to define the acidity or basicity of a solution, is the negative logarithm of the Deleted: in the system…n a pH control ... [11] hydrogen ion activity as shown in the equation below: Brice Poston ! 9/1/13 4:00 PM ... [12] pH = - log aH Deleted: s of…pH concept control …ncluding Rob ! 8/30/13 7:34 PM Ion activity (a) can be mathematically expressed as: Deleted: described. S Brice Poston ! 9/1/13 12:43 PM a = γC Deleted: so…utions to these problems are... [13] where γ is the activity coefficient and C is the hydrogen ion concentration. Rob ! 8/30/13 7:34 PM Deleted: and pH is usually measured using a combine pH glass electrode made of doped glass membrane sensitive to Brice Poston ! 9/1/13 12:44 PM hydrogen ion and a built-in reference electrode. Oftenly, the glass electrodes are either bulb-type or flat- Deleted: , are discussed. type, depending on the structure of the electrode tip. In general, the pH probe is oftenly considered the Brice Poston ! 9/1/13 12:44 PM weakest link in a pH control system since it is prone to failure and requires frequent checking and calibration. Deleted: sensors Rob ! 8/30/13 11:17 AM Aside from the pH electrode and transmitter that relays the signal, a typical pH control system consists of Deleted: a feedback controller, a control valve, and a mixing equipment. In general, wastewater pH control system Brice Poston ! 9/1/13 5:41 PM include an equalization tank and chemical tanks as source of reagent feed. Despite this relatively simple Formatted ... [14] system, pH control can be a complex process. One reason is that in water applications, the system Rob ! 8/30/13 11:18 AM deals with a wide range of hydrogen concentration, that is from 10-14 to 1 M. No other common Formatted wastewater quality parameter is measured at such wide range. Another reason for the complexity of pH ... [15] control system is that for the system to work effectively, proper design and installation of all components Brice Poston ! 9/1/13 10:00 PM are extremely necessary. Correct functioning of the pH electrodes, transmitter, controller, control valves, Formatted ... [16] piping and mixing equipment should be maintained at all times. Neutralization reactions with an acid or Rob ! 8/30/13 5:17 PM base occur instantaneously in most cases and therefore requires control systems to react accordingly. Deleted: or the power of hydrogen is Brice Poston ! 9/1/13 3:42 PM A Practical Approach to pH Control Deleted: E…uation below1 ... [17] Brice Poston ! 9/1/13 4:01 PM Formatted ... [19] Brice Poston ! 9/1/13 3:42 PM Deleted: . Brice Poston ! 9/1/13 4:01 PM Formatted ... [18] Brice Poston ! 9/1/13 3:43 PM Rob ! 8/30/13 8:47 PM Formatted ... [20] Brice Poston ! 9/1/13 10:00 PM Formatted ... [21] Rob ! 8/30/13 8:47 PM Formatted ... [22] Brice Poston ! 9/1/13 3:43 PM Unknown Brice Poston ! 9/1/13 4:02 PM Formatted ... [23] Brice Poston ! 9/1/13 3:43 PM Brice Poston ! 9/1/13 10:00 PM Formatted ... [24] Brice Poston ! 9/1/13 3:43 PM Rob ! 8/30/13 9:02 PM ... [25] Brice Poston ! 9/1/13 10:28 AM ... [26] Rob ! 8/30/13 7:36 PM Formatted ... [27] Brice Poston ! 9/1/13 10:29 AM Rob ! 8/30/13 7:36 PM ... [28] Brice Poston ! 9/1/13 10:32 AM ... [29] Brice Poston ! 9/1/13 4:50 PM Formatted ... [1] Brice Poston ! 9/1/13 10:01 PM Formatted ... [31] Brice Poston ! 9/1/13 10:41 AM Deleted: Fundamentals of pH control including... [32] Rob ! 8/30/13 11:40 AM In this work, different pH control system designs were evaluated to determine potential issues that may Deleted: be encountered in the plant. Common problems and design pitfalls observed during system startups are Brice Poston ! 9/1/13 5:41 PM described in the discussion below. By presenting these observations from different pH control systems Formatted ... [33] over the past year at various softdrink facilities, system failure which could be costly, and sometimes Rob ! 8/30/13 11:18 AM catastrophic, may be prevented. Formatted ... [34] Brice Poston ! 9/1/13 3:36 PM METHODOLOGY Deleted: Designs of pH control systems ...by [35] two Brice Poston ! 9/1/13 10:01 PM Evaluation of commonly used pH probes was performed using three commercially available pH electrodes. Two bulb type sensors and one flat-type electrode were used. All probes were calibrated on a Formatted ... [36] daily basis prior to testing. The pH probe testing was performed by submerging all electrodes in a Brice Poston ! 9/1/13 3:37 PM synthetic softdrink plant wastewater. Response due to acid and base addition was recorded. A Deleted: In addition to on-site evaluation... of [37] the comparison of each probe’s response time, steadiness of reading, noise, and slope of pH change over Rob ! 8/30/13 11:18 AM time was conducted to determine the ideal electrode for the softdrink plant wastewater pH control system. Deleted: testing Brice Poston ! 9/1/13 3:37 PM Designs of pH control systems by two different companies were reviewed and implemented in a number of softdrink plants. These softdrink plants were located in various sites in Northern America. Merits and Deleted: also …erformed using three four... (4)[38] pitfalls for each design were evaluated and confirmed on-site through a series of Site Acceptance Tests Rob ! 8/30/13 11:19 AM (SAT). Deleted: Brice Poston ! 9/1/13 12:48 PM RESULTS AND DISCUSSION Deleted: type while the onether sensor was... [39] a Rob ! 8/30/13 4:43 PM pH Probe Comparison Deleted: Brice Poston ! 9/1/13 10:01 PM The pH response for each probe during chemical adjustment was monitored and recorded. These data Formatted ... [40] were analyzed to compare probe performance. Each probe was evaluated for steadiness of the probe Brice Poston ! 9/1/13 11:19 AM reading, presence of noise, and slope of pH change per time. Deleted: (Add description of test). As expected, proximity to the chemical feed point affected the performance of the electrodes. It was Rob ! 8/30/13 7:39 PM observed that the closer the electrode is to the chemical feed point, the more variable are the recorded Deleted: pH readings (up to ±1.5 pH units variability), which would be expected due to concentration gradients of Rob ! 8/30/13 7:39 PM the chemical as it mixed into the wastewater. This erratic readings were particularly observed for Probe Deleted: ... [41] 2, a flat tip sensor. The bulb-type electrodes also exhibited some erratic readings but were minimal. Brice Poston ! 9/1/13 5:41 PM Results also indicate that the flat tip pH probe is more prone to unstable measurements. In general, flat Formatted ... [42] tip probes have higher impedance and slower speed of response while hemispherical or spherical bulb probes have lower impedance and faster response speed.
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