The Energy Water Nexus
The treatment and pumping of water and wastewater requires a large amount of energy. Several thousand kilowatt-hours are typically required for each million gallons of water treated and pumped. In many cities, municipal water and wastewater plants are among the largest individual customers of the local electric utility.
Energy is often the 2nd or 3rd largest component in the annual operating budget of a water or wastewater utility. There are multiple reasons for this. For drinking water / potable water systems, typical energy drivers include the quality of the raw water supply, the required elevation lifts from either the groundwater or surface water source, the type of treatment and disinfection needed, the degree of leakage in the system, the desired pressure at the customer’s tap, the amount of storage available, and the extent and condition of the distribution network.
In a wastewater / water reclamation system, typical energy drivers are the strength of the raw wastewater, the biological treatment processes which often require extensive use of blowers and/or mixers, the amount of pumping required inside and outside of the plant, and the degree to which methane can be recovered from the plant’s biosolids / sludge processes.
Overall system reliability and required levels of service are typically at the top of a utility’s must-do-list, and energy is sometimes considered as just one of the necessary inputs. However, while energy reduction should not be pursued at the expense of reliability or service, most treatment and pumping operations have major opportunities to reduce energy usage without negatively affecting performance. In fact, in many cases energy conservation practices can actually improve system reliability and reduce down-time.
A practical energy analysis can identify the opportunities that would be most effective within your own plant or system.
To learn more, contact:
Ned Paschke, PE, DEE