DISSOLVED OXYGEN - Fondriest

5 Dissolved Oxygen Meters Dissolved Oxygen Meters 6 SELECTION FACTORS FOR A DO METER Field Ruggedness Ruggedness in the field is an important factor when selecting a dissolved oxygen meter. A field meter must protect against dust and dirt while maintaining water resistance. The most rugged field meters are completely protected against dust and can withstand powerful water jets without being damaged. Impact resistance and the ability to calibrate and instrument in the field also add to a meter’s usefulness as well. Sensors that are only suited for lab work should not be used in the field; they may not be protected from the elements, and this can result in expensive damage to the equipment. YSI’s Pro Series of water quality meters meet the demands of true field work. This family of meters includes the YSI Pro20, which can perform both polarographic and galvanic readings, and the ProODO, which utilizes luminescent optical dissolved oxygen technology. These instruments are rated to IP-67 standards even without the battery cover on. Other tough features include Mil-spec connectors and rubber over-molded cases. In-house testing procedures also include one-meter drop tests from all angles to ensure expected field-durability. To meet the needs of various applications, cables are available in lengths from 1 to 100 meters. Application Needs Each application has unique needs for a dissolved oxygen meter. Project requirements related to flow dependence, warm-up time, measurement range, and interference should be considered carefully. have a longer sensor lifetime, since there are no electrodes to polarize. Although they can begin taking a reading instantly, however, optical units usually require about 35-40 seconds to reach a 90-percent-accurate reading (Known as a T90 response time). Flow independence is especially important in still water. Electrochemical sensors consume oxygen while taking readings, thus they require either sample movement or must me stirred while a reading is being taken. Without it, inaccurate data can result from the artificial depletion of oxygen in the area by the sensor. The flow-independent technology of optical sensors is ideal for readings in still water and requires no stirring. Accuracy within the intended range of measurement is vital. Many modern electrochemical and optical DO sensors, such as the YSI Pro20 and ProODO, can produce accurate results across a large measurement range if used properly. However, one should still ensure an individual sensor’s acceptable DO saturation range accommodates the expected DO levels of sampling sites. A long warm-up time can be detrimental in some situations. Between the two membrane sensor technologies, galvanic sensors are faster and more convenient. These sensors can take readings with no warm up time, but this is at the cost of sensor longevity. Polarographic sensors, on the other hand, typically require 5-15 minutes to warm up before use, but they have a longer sensor life and have more extensive warranty coverage than their galvanic counterparts. Optical sensors carry the advantage of no warm-up time and The most commonly overlooked aspect of dissolved oxygen sensors is interference. There are certain gases and liquids that will interfere with making quality measurements. The sensor type determines what will interfere with accurate readings. Some sensors are vulnerable to chemicals that can damage the probe’s materials, such as acetone and benzene for optical sensors. Polarographic and galvanic sensors in particular are susceptible to interference from high concentrations of certain gasses, such as hydrogen sulfide. One should also be mindful of potential interference from chemicals coating the membrane surface or obstructive biofouling. Cost of Ownership Maintenance kit costs vary greatly among meters, and the length of time between required maintenance determines how many kits are needed per season. Optical sensors usually require a higher initial investment, but since they do not rely on electrolyte solution and membrane caps, they need considerably fewer part replacements. Some dissolved oxygen meters, such as YSI’s Pro Series sensors, are now manufactured with detachable sensors, which can also lower the overall cost of ownership. Finally, cost of ownership also includes the time it takes to perform maintenance. The best probes require less than five minutes for regular maintenance with affordable kits that provide long-lasting performance. Screw-on caps and field-replaceable electrodes,and electrolyte-free solutions all help to reduce the amount of labor needed to maintain equipment. Maintenance and Warranties Regardless of the sensors used, periodic maintenance and calibration are required. A meter that is easy to maintain can prevent a great deal of difficulties in the field as well as help avoid bad data. The most frequent task for any electrochemical-based DO sensor is replacing the permeable membrane that covers the electrolyte. Membranes should typically be changed every 2-8 weeks, depending on the application and site conditions. Electrochemical DO sensors usually come with one of two membrane types. Traditionally, the membrane has been designed to stretch over the sensor and held in place by an O-ring. YSI, however, now offers screw-on, cap-style membranes for its Pro Series sensors. These caps are significantly easier to change and make quick maintenance possible. Membrane caps should be partly filled with fresh electrolyte and then threaded onto the probe. Without fragile membranes or electrolyte to replace, optical DO sensors require much less maintenance than electrochemical models. These units can usually be cleaned by being rinsed with clean water and a lint-free cloth. Optical DO sensors also have more durable sensing elements than membrane-based DO sensors. Optical technology has changed DO sensors from being one of the highest maintenance sensor types to one of the lowest.The sensing element usually only needs to be replaced in one-year intervals or longer. Over time, the electrodes of an electrochemical DO sensor will also wear. As a natural result of the process taking place within the electrolyte, electrodes will begin to tarnish. Polarographic probes typically require annual electrode maintenance and cleaning, while galvanic units must be cleaned about once every three months. YSI’s Pro20 contains electrodes that can be removed or replaced in the field, which simplifies this maintenance and reduces the cost of ownership. When problems extend beyond user maintenance, some vendors provide warranties for instruments, cables, and even probes. Some of this warranty coverage is provided for as long as three years of use. Length of warranty and the amount of coverage offered should be seriously considered when choosing a DO meter. YSI offers industry-leading warranty coverage on its Pro Series meters. This includes a three-year instrument and two-year cable warranty, as well as two years for optical sensors, one year for polarographic, and six months for galvanic units.

7 Dissolved Oxygen Meters Dissolved Oxygen Meters 8 RECOMMENDED DO METERS Technology Comparison Although many methods are available for measuring dissolved oxygen, our experience has led us to recommend DO meters from YSI’s Pro Series. Please see product summaries for the Pro 20 membrane-based sensor and the Pro ODO optical dissolved oxygen below. A comparison of galvanic, polarographic, and optical meters is also provided in this section. YSI Pro20 DO Meter The new Pro20 handheld dissolved oxygen and temperature meter is ideal for use in the lab or field. Utilizing YSI’s durable MS (Military Spec) cable connector, the instrument can accept rugged field sensors (galvanic or polarographic) or a self-stirring lab BOD sensor. To meet the needs of various applications, cables are available in lengths from 1 to 100 meters. The included cable management kit even makes the use of long cables easy and convenient. The Pro20 is YSI’s first dissolved oxygen instrument to offer a convenient “One Touch Cal” feature for air calibrations. This unique feature, along with others like user replaceable sensors, simplifies operation and saves time and money.The Pro20 is completely waterproof, withstands 1-meter submersion and has an industry-leading 2-year cable warranty making it worthy of your demands in the field. One Touch Cal feature allows you to calibrate in % mode with the press of a button I P67 waterproof, Military Spec connectors, rubber over mold, 1-meter drop test 3-year instrument warranty; 2-year cable warranty Polarographic Optical Average Sensor Life 2-3 yrs 3-5 yrs 10 yrs Average Membrane Life 2-8 wks 2-8 wks 1 yr Warm-Up Time - 5-15 min - Response Time (T95) 8 sec 8 sec 40 sec calm 25 sec stirred Flow Dependence 22% 22% 0% Required Flow Rate 6 in/s 6 in/s - User Required Maintenance YSI Pro20 YSI ProODO Optical DO Meter The new ProODO provides traditional YSI quality in a handheld dissolved oxygen instrument with luminescent optical dissolved oxygen (DO) technology.The ProODO utilizes smart digital sensor technology which stores calibration data within the sensor. This allows probes to be placed on any ProODO instrument without re-calibration. YSI ODO technology reduces the time required calibrating and maintaining sensors while utilizing a user replaceable sensing element that requires approximately an annual replacement. There are no electrodes to clean or solutions to change. Calibrations are stored in each sensor and, based on usage, can be stable for up to one year. Optical technology also increases accuracy and eliminates probe fouling by common gases such as hydrogen sulfide. Non-consumptive luminescent method eliminates the need for stirring User-replaceable cables in lengths of 1 to 100-meters Stores 2000 data sets (sensor data, date, time, site and user defined information) Galvanic Average Time to Perform Maintenance 20 min 20 min Clean gasket, replace membrane cap, recaibrate 5 min Interfering Gases Hydrogen sulfide, sulfer dioxide, halogens, neon, nitrous and nitric oxides gases - Interfering Liquids Acids, Caustics, Solvents Alcohol and organic solvents Accuracy 0-200% 2% of reading or 2% saturation, greater of 1% of reading or 1% saturation, greater of Accuracy 200500% 6% of reading 15% of reading Accuracy 0-20 mg/L 0.2 mg/L or 2% saturation, greater of 0.1 mg/L or 1% saturation, greater of Accuracy 20-50 mg/L 6% of reading 15% of reading Short Term Storage YSI ProODO Replace membrane and electrolyte, recondition electrode, recalibration Long Term Storage Moist storage sleeve Completely dry Moist storage sleeve

9 Dissolved Oxygen Meters Dissolved Oxygen Meters 10 DO MEASUREMENT APPLICATIONS Spot Sampling SHORT-TERM PROJECTS Rental vs. Purchase There are many applications for spot sampling with dissolved oxygen meters, including aquaculture, surface water monitoring, process monitoring for industrial facilities, regulation compliance, respiration studies, down-well sampling and many more. While it often makes sense to purchase meters outright, many short-term projects make it cost-prohibitive. Fondriest Environmental offers real-time DO meters with weekly and monthly rental rates to meet project requirements. Fondriest can lease all the necessary monitoring equipment as well as field supplies needed to set up and use a DO meter. These spot check measurements are best performed with a high quality and reliable hand-held dissolved oxygen meter that is easy to use and easy to maintain. For additional product details see: http://www.fondriest.com/products/ysi proodo.htm http://www.fondriest.com/products/ysi pro 20.htm Biological Oxygen Demand (BOD) Biological oxygen demand is the uptake rate of dissolved oxygen by the biological organisms in a sample of water. This is determined by measuring the amount of dissolved oxygen consumed by a sample over a period of time. These types of applications are best performed with handheld dissolved oxygen meters with BOD probes such as the YSI Pro20 or laboratory BOD instruments. For additional product details see: http://www.fondriest.com/parameter/bod.htm Continuous Monitoring In some cases, continuous monitoring can provide greater depth to dissolved oxygen measurements than incremental sampling alone. Common applications for continuous monitoring with dissolved oxygen sensors include: aquifer monitoring, down-well monitoring, stream sampling, dredge monitoring, algae bloom monitoring, lake profiling, unattended monitoring and more. These continuous monitoring projects are best preformed with high-quality and reliable dissolved oxygen sondes. The equipment options for continuous monitoring systems are not covered in this guide. For more information about this option, call or email a Fondriest application engineer. For additional product details see: http://www.fondriest.com/products/multi-parameter sondes.htm YSI BOD Fondriest Environmental application engineers are available to assist in configuring an ideal solution for your project needs. They can also help with training and technical support. To reach them, please call (888) 426.2151 or email customercare@fondriest.com. Fondriest offers both extensive field experience and a wide array of deployment hardware to facilitate seamless implementation of a DO meter. Moreover, if existing solutions are not suitable for a new project, Fondriest engineers can design custom platforms, sensors, and adaptations to suit a growing list of unique applications. Fondriest Environmental, Inc. 1415 Research Park Drive Beavercreek, OH 45432

11 Dissolved Oxygen Meters Dissolved Oxygen Meters 12 APPLICATION: ECSI Manages Habitat in High Hydrogen Sulfide Environments Using Optical DO Project Overview PSEG, a New Jersey power generation company, has worked with the states of Delaware and New Jersey to construct fish passage facilities at twelve dams along tributaries of the Delaware River and Bay to restore fish habitat within the Delaware River Basin.The basin comprises 13,539 square miles, including portions of Delaware, New Jersey, New York, and Pennsylvania. Environmental Consulting Services Inc. (ECSI), of Middletown, Delaware has been maintaining and monitoring the success of the fish ladders during the spring spawning migrations of Alewife (Alosa pseudoharengus) and Blueback herring (Alosa aestivalis). System Description A fish ladder is a structure on or around artificial barriers (such as dams and locks) to facilitate natural fish migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps into the waters on the other side. Initially, spawning condition fish were moved from below the dams and released in the lakes to provide a stock of fish with an instinct to home on the upstream spawning grounds. In subsequent years returning spawning run herring are counted utilizing the ladders. Since the first Alaska Steeppass fish ladders were constructed in 1996, anadromous fish access has been restored to 1,001 acres of impounded habitat and 133 miles of stream habitat previously made inaccessible by man-made obstacles. The Alaska steeppass is a prefabricated, modular style of Denil fish ladder originally developed for use in remote locales.The steeppass is a relatively economical, lightweight fishway, where one 10-foot aluminum unit weighs only about 1,500 pounds. The watershed types of the newly opened habitat include forest, cultivated agricultural land, residential, and dense urban land. This diversity of land use results in differences in point and nonpoint discharges of water into the streams. Measuring water conditions is a significant part of the overall monitoring program. ECSI has been using YSI temperature, salinity, and dissolved oxygen handheld meters to evaluate the water quality for many years. These meters have proven to be real work horses for ECSI in the numerous monitoring programs. They currently maintain ten meters for use on various fisheries monitoring projects in the Mid-Atlantic region. Several years ago, ECSI installed YSI multiparameter sondes in the lower Delaware River for continuous water quality monitoring. They employed the YSI ROX optical dissolved oxygen probe and found that the probe maintains calibration for up to eight weeks in their monitoring application. Due to the nature of the optical technology, it is resistant to the hydrogen sulfide contamination experienced with polarographic sensors. High levels of hydrogen sulfide exist in certain areas along the Delaware River Basin and can cause electrode fouling and additional cleaning requirements on traditional membrane covered sensors. Optical sensor technology eliminates the membrane and subsequent fouling issues when used in high hydrogen sulfide environments. Using optical technology allows ECSI to eliminate the maintenance of cleaning the anodes which are susceptible to hydrogen sulfide interferences. Additionally, in 2008, ECSI started using the YSI ProODO handheld optical dissolved oxygen meter. ECSI indicates it is simple to use, calibration is required infrequently, and there are no membranes that are susceptible to fouling and replacement. Most importantly, the probe can be used in high concentrations of hydrogen sulfide without contamination and slowing of response time. The meter has been rugged; it is carried around in a bucket and has even fallen onto a concrete dam face without sustaining damage. For ECSI, the optical DO technology has been a blessing in their high hydrogen sulfide environments and the ruggedness of the YSI products have been invaluable to their extensive field work. The Delaware River

13 Dissolved Oxygen Meters Dissolved Oxygen Meters 14 SYSTEM CONFIGURATION TOOL Membrane Lifetime Fondriest product specialists will assist with finding the right meter to suit a specific application. The questionnaire below can help us make the best recommendation. Once completed, this form can be faxed to (937) 426.1125 or, if completed digitally, emailed to customercare@fondriest.com. Polarographic and galvanic DO sensors have sensitive membranes that typically require replacement every 2-8 weeks. While optical sensors are usually a costlier initial investment, their membranes can last longer than one year before requiring replacement. Longer Membrane Lifetime (Optical sensor) Shorter Membrane Lifetime (Galvanic/Polarographic sensor) Contact Information Name: Project Length (Rental vs. Purchase) Organization: Although it often makes sense to purchase a meter outright, many short-term projects make it cost-prohibitive. Fondriest Environmental offers a wide selection of dissolved oxygen meters with weekly and monthly rental rates to accommodate these applications. A product specialist can make recommendations on what choice is most cost-effective. Telephone: 1-3 Months 3-6 Months 6-12 Months 1 year Email: Additional Comments Site Location Sampling location can affect what kind of DO sensor best suits the conditions. Please select in what type of water body the meter will be used primarily. Lake River Coastal Other Stir Independence Some dissolved oxygen sensors, typically ones with optically based membranes, can measure oxygen without consuming it. This eliminates the need to stir the sensor while taking a reading in still waters. This is less of an issue in rivers and streams with high flow rates. Is stir-independence preferred? Yes No Sensor Lifetime vs. Warm-Up Speed While some dissolved oxygen sensors, such as galvanic probes, require little warm-up time before taking a reading, it is at the expense of a longer sensor lifetime. Polarographic sensors, on the other hand, last considerably longer but require a 5-15 minute warm up. Faster Warm-Up Speed Longer Sensor Life If you have any questions, concerns, or comments you’d like to discuss when speaking with a Fondriest product specialist, please include them in the space provided below.

dissolved oxygen. Dissolved oxygen is reported as milligrams per liter (mg/L), parts per million (ppm), or as percent air saturation (% Sat). 1 mg/L is equal to 1 ppm. 100% air saturation refers to the maximum amount of dissolved oxygen that a sample of water can hold at equilibrium. There are several common methods for determining dissolved .