Wastewater Effluent is Hot – Capturing Effluent Heat for Swimming Pools and Snowmelt Systems

The Town of Avon, Colorado, and the Eagle River Water & Sanitation District in Eagle County, partnered to construct a district heating system based on the recovery of low grade heat in wastewater effluent. The system uses a heat pump to capture heat from the Avon Wastewater Treatment Plant (WWTP) effluent and push it through a district heat loop running between the WWTP and the center of town. Heat is extracted from the loop to provide space heat for town ;amp;#x2013; and district-owned buildings and swimming pools in the community recreation center. In the future a snowmelt system will be connected to the district heat loop to melt snow on roads and sidewalks in the downtown corridor.The district heating system consists of two main buildings and an 200 mm (8-in) pipe that circulates between the buildings. The heat pump building is on the WWTP grounds and houses the heat pump and the heat recovery loop pumps. Adjacent to the WWTP is an effluent wet well, which pumps wastewater through the evaporator side of the heat pump. The heat distribution building is located in the downtown corridor of Avon. This building houses the recreation center pool heat exchangers (for the Jacuzzi, lap, slide, and leisure pools) and a supplemental boiler. The building is large enough to allow the installation of a future snowmelt system, which will be installed in an upcoming project and will be capable of melting snow on as much as 6,040 m2 (65,000 ft2) of roads and sidewalks. The heat distribution system and the WWTP are located about 0.8 km (0.5 mile) apart.The heat recovery system was started up in February, 2011. Data recorded to date show that the system has produced over 1,500 GJ (1.4 million BTU) of heat. The electrical demand for the system has been just under 200,000 kw*hr. Over a similar seasonal period in past years the Town of Avon has used about 3,600 GJ (3.4 billion BTU) of natural gas for heating the pools, domestic hot water, and space heating. Since the startup of the heating district system the Town has reduced its recreation center natural gas demand by approximately 1,800 GJ (1.7 billion BTU) of natural gas relative to previous years. Converting to common units, the heating district has currently supplied 158 kW of power as heat at an electrical power draw of approximately 92 kW. The net carbon impact of the operation of the heating district system is an estimated reduction in carbon dioxide emissions of over 23 tonne (25 ton) per month.