Strategy 4- Carbon Optimization
Utility or well-connected denitrification systems often do not see much short term variation in the incoming nitrate levels. Most of these systems can be operated successfully with a minimal or manual control system. However, irrigation effluent nitrate concentrations can vary dramatically. With a fixed carbon input, you may use too much carbon when NO3-N levels are low and not provide enough carbon when NO3-N levels are high. How to best optimize your nitrate removal system to accommodate this challenge?
For best results- Adjust your carbon supply to match changing Nitrate levels
ORP Measurements can be used to Control Denitrification
Instrumentation solutions can help you adjust the carbon levels. But they increase the need for periodic calibration and cleaning. If you are new to biological denitrification, an oxidation-reduction potential (ORP) sensor is a good choice. But remember: ORP does not tell you NO3 levels. It provides a relative indication. The general range of values for ORP is -50mV to + 50mV. But this value depends on where you measure ORP. Measuring deep inside the reactor probably gives you the best perspective but measuring ORP at the outlet is much easier to install and maintain. Continuous ORP measurements can provide valuable inputs for a more comprehensive algorithmic approach.
You can use information you already have to develop a control algorithm for carbon injection that does not rely on an expensive laboraratory instruments. We know that water usage and nutrientt uptake by plants are strongly affected by solar insolation, temperature, and humidity. Additionally, crops at different stages of growth will require different front end inputs. Nitrate levels in the effluent can spike when it gets very hot outside as water usage by the crops increase (transpiration). The great news: you have all the evapotranspiration data already! We just need to match this tot he nitrate levels and we can help you craft a very flexible information driven algorithm that can be updated dynamically from your phone or computer/tablet.