Many small to medium municipalities may only monitor industrial discharges monthly, quarterly, or as infrequent as semi-annually.
In the odor complaint example above, an extremely negative ORP reading in the collection system downstream of an industrial discharger provides wastewater operations staff with valuable information regarding the relative strength of the discharge without the need to install a composite sampler to monitor the industrial discharger. This is intended to protect both the collection system from deterioration and the treatment facility from treatment upsets caused by toxics or slug loads. The solution could be chemical dosing of oxidizers or other odor control agents, or it could point to a problem with an industrial discharger, which leads to the next ORP monitoring benefit.īoth toxic and slug loads are often prohibited by municipal sewer use ordinances. Once the location of the odor is determined, operations staff can be provided with information on how best to address the odor formation.
By using a portable ORP probe and monitoring manholes around the complaint site at different times of day or days of the week, the source can be pinpointed. It can be difficult to predict when and where odors form when complaints occur. Under any of the above conditions, the potential exists for odors to form, which can lead to complaints. Collection systems can have several characteristics leading to anaerobic conditions such as: A day in the field using an ORP probe can gain valuable data that can help the design process.įollowing are some of the ways in which wastewater treatment systems can be optimized by using ORP probes.Īs noted, ORP provides a measure of the oxidative or reducing ability of a solution, with reduced conditions being more anaerobic in nature. What’s more, according to Schaefer, ORP measurements can be a huge benefit when designing new plants or treatment processes. By measuring these processes, operators get a better understanding of how their system is performing to help them optimize their operation. Operations staff that manage facilities designed for BNR (either nitrogen, phosphorus or both) may already be familiar with the use of ORP probes in that application, but there are many more functional uses for ORP probes. DO probes cannot accurately report results less than about 0.5 mg/L. ORP probes are most commonly used to extend the measurement range of DO probes. In cases where there are multiple cells in the anaerobic selector basins, wastewater operators can modify the cells where raw wastewater and return activated sludge flows are introduced into the anaerobic selector basins to develop anaerobic conditions for phosphorus accumulating organisms to survive. Wastewater operators can adjust return activated sludge flow rates and internal nitrate recycle flow rates to the anaerobic selector and/or anoxic basins to maintain targeted conditions in each type of basin. But, in anaerobic or anoxic basins looking to achieve biological nutrient removal, these are not ideal conditions. Positive ORP readings show dissolved oxygen is present in the water, which is ideal in aeration basins. Conversely, the more negative the reading, the more concentrated reducing agents like hydrogen sulfide are present, making the system more anaerobic. The more positive an ORP reading is, the more concentrated the oxidizers such as dissolved oxygen are and more likely the system is to be aerobic. The device uses millivolts (mV) to measure electrical potential. To measure it, the process uses a probe with one inert electrode and one reference electrode attached to a pole. It is also causing them to adapt to new treatment schemes and automate process control all while reducing energy consumption.Īccording to the Molecular Hydrology Institute, Oxidation Reduction Potential (ORP) is a way to measure water’s ability to either release or accept electrons during a chemical reaction. Second, increasingly stringent effluent limitations are causing operators and engineers alike to reconsider longstanding biological operating parameters in order to optimize existing treatment processes. These variables can result in vastly different effluent quality requirements that must be met to comply with regulations. Here, we reveal how an oxidation reduction potential (ORP) probe can help you meet compliance regulations and optimize operations.įirst, effluent compliance requirements are driven by discharge location, receiving water classification and level of impairment. Effluent requirements are becoming more stringent than ever with total maximum daily loads (TMDLs) and water quality-based effluent limitations (WQBELs) replacing longstanding, technology-based limits such as biochemical oxygen demand (BOD), total suspended solids (TSS), ammonia and phosphorus.