Aerial view of Central Marin Sanitation Agency wastewater treatment plant, <a href="https://en.wikipedia.org/wiki/San_Rafael,_California" class="extiw" title="w:San Rafael, California">San Rafael, California</a>.
U.S. EPA
circa 2016 <div style="display: none;">date QS:P,+2016-00-00T00:00:00Z/9,P1480,Q5727902</div>
U.S. Environmental Protection Agency (EPA), Philadelphia, PA. <a rel="nofollow" class="external text" href="https://www.epa.gov/anaerobic-digestion/types-anaerobic-digesters">"Types of Anaerobic Digesters: Digesters at Water Resource Recovery Facilities."</a> <i>Anaerobic Digestion.</i>