What resource recovery opportunities exist in wastewater treatment and how are they implemented?

Modern wastewater treatment increasingly emphasizes resource recovery over simple waste treatment. Energy recovery: Anaerobic digestion of sludge produces biogas for CHP or upgrading; energy-positive plants achieving net energy production; thermal hydrolysis pretreatment (Cambi, Exelys) increases gas yield. Nutrient recovery: Phosphorus - struvite crystallization (Ostara, NuReSys) produces slow-release fertilizer; enhanced biological phosphorus removal concentrates P in sludge. Nitrogen - ammonia stripping and recovery; anammox reduces energy while producing N2. Potassium - recovery with struvite variants. Water recovery: Direct and indirect potable reuse; industrial reuse; agricultural irrigation; membrane and advanced treatment technologies; Singapore NEWater, Orange County GWRS. Biosolids valorization: Class A biosolids for land application; pyrolysis to biochar; gasification for syngas. Cellulose recovery: Screens recover cellulose fibers from influent for paper, composites, biofuels. Bioplastics: PHA production from wastewater organics using mixed cultures; pilot scale implementations. Implementation considerations: Market development, quality standards, regulatory acceptance, public perception, economics, facility integration.