Abstract: Disclosed are methods and systems for minimizing downtime for waste processing plants by serially processing a potentially mixed waste stream including a solid fraction, low-strength wastewater, and/or high-strength wastewater in a plurality of anaerobic digesters (e.g., plug flow, upflow and fixed-film), and treating the processed liquid output with a plurality of tertiary wastewater treatments (e.g., ultrafiltration, reverse osmosis, precipitation), to produce a low suspended solids liquid and a high suspended solids liquid, and returning at least a portion of the high suspended solids liquid to the plurality of anaerobic digesters.