The Water Reclamation Plant has a complex energy management system leading the way for green infrastructure in the Rochester community. Energy management at the facility reduces operating costs and allows for some energy production as a byproduct from treating wastewater. Primary energy conservation components include heating and cooling loops, methane gas production utilized in boilers and engine generators, wastewater heat exchangers, ongoing efficiency upgrades on air usage, lighting, and motor replacements. The energy management program saves over $600,000 annually and continues to grow. An additional $200,000 of energy savings occurred in 2014 through process modifications, lighting replacements, air audits, and motor replacements which will be realized every year moving forward.
Methane gas is produced from our solids treatment process and is used to produce heat and electricity from our engine generators and boilers. The methane gas is collected from an anaerobic solids treatment process and is compressed and cleaned prior to use. Methane gas can be used in one of two 1 Megawatt engine generators to produce electricity and recover heat for plant processes/buildings or can be used by one of four boilers during the winter months to heat plant processes/buildings. Annual methane recovery averages 130,000 Mcf which equates to $600,000 in natural gas savings. Methane recovered and used in our engine generators reduces annual electrical costs by $380,000.
Heating and Cooling Loops
Heating and cooling loops are used to conserve energy during the varying seasons and temperatures found in Minnesota. Low, medium, and high temperature loops are used to transfer heat throughout the plant. Both the low and high temperature loops are used to maintain adequate heating and cooling in many of the facility's buildings by recovering heat from effluent wastewater heat exchangers, and boiler or generator heat exchangers. Also, the recovered heat from generators allows the WRP to operate during summer months without needing to run boilers to heat solids treatment processes. The entire system has been engineered to heat and cool the majority of the WRP by energy produced from the wastewater treatment process.
Plant Air Usage
The WRP uses large efficient blowers to supply air or high purity oxygen to wastewater treatment processes. Blowers onsite range from 200 hp to 600 hp supply air to both the High Purity Oxygen and Activated Sludge Plants. Blower usage is closely monitored to only supply air necessary to treat the wastewater in order to minimize electricity costs. The WRP uses 100 hp air compressors to operate valves and miscellaneous pumps throughout the facility. Staff routinely performs air audits on the plant air system to reduce operating costs and correct failed pneumatic equipment.
Purchasing energy efficient products is smart business and the WRP uses all sources available to find the perfect efficient product for each application. Premium efficient motors are used throughout the facility to run equipment and are often equipped with variable frequency drives to allow operational flexibility and reduce energy demand. Energy star rated lighting upgrades continue to occur annually throughout the facility. Motion sensors and photocells, in combination with effective lighting layouts, greatly reduce energy demand and maintenance required to change bulbs.