Energy Conservation
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 enables some energy production as a byproduct of wastewater treatment. 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 in energy savings occurred in 2014 through process modifications, lighting replacements, air audits, and motor replacements, and these savings will be realized every year moving forward.
Methane Utilization
Methane gas is produced from our solids treatment process and used to generate heat and electricity for our engine generators and boilers. Methane gas is collected from an anaerobic solids treatment process and 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 in 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 & Cooling Loops
Heating and cooling loops are used to conserve energy during Minnesota's varying seasons and temperatures. 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 from boiler or generator heat exchangers. Also, recovered heat from generators enables the WRP to operate during summer months without running boilers to heat solids treatment processes. The entire system has been engineered to heat and cool the majority of the WRP using energy generated by the wastewater treatment process.
Plant Air Usage
The WRP uses large, efficient blowers to supply air or high-purity oxygen to wastewater treatment processes. On-site blowers range from 200 hp to 600 hp and supply air to both the High Purity Oxygen and Activated Sludge Plants. Blower usage is closely monitored to supply only the air necessary to treat wastewater, minimizing electricity costs. The WRP uses 100 hp air compressors to operate valves and miscellaneous pumps throughout the facility. Staff routinely perform air audits on the plant air system to reduce operating costs and correct failed pneumatic equipment.
Efficiency Upgrades
Purchasing energy-efficient products is smart business, and the WRP uses all sources available to find the perfect efficient product for each application. Premium-efficiency motors are used throughout the facility to run equipment and are often equipped with variable-frequency drives to provide operational flexibility and reduce energy demand. Energy Star-rated lighting upgrades continue annually throughout the facility. Motion sensors and photocells, in combination with effective lighting layouts, greatly reduce energy demand and maintenance required to change bulbs.