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Although aluminum-and iron-based chemicals have been broadly used as the two most common types of coagulants for wastewater treatment, their impacts on the performance of downstream sludge management can be quite different and have not been well understood. This work reviewed and analyzed their similarities and differences in the context of the anaerobic digestion performance, dewaterability of digested sludge, and odor emission from dewatered biosolids. In short, iron-based coagulants tend to show less negative impact than aluminum-based coagulants. This can be attributed to the reduction of ferric to ferrous ions in the course of anaerobic digestion, which leads to a suite of changes in protein bioavailability, alkalinity and hydrogen sulfide levels, and in turn the sludge dewaterability and odor potential. Whether these observations still hold true in the context of thermally hydrolyzed sludge management remains to be studied. Practitioner Points• The impacts of aluminum-/iron-based coagulant addition on municipal sludge anaerobic digestibility, dewaterability, and odor emission are reviewed.• Iron-based coagulants show less negative impact on the sludge digestibility than aluminum-based coagulants.• Conclusions may aid practitioners in selecting coagulants in practice and better understanding the mechanisms behind the phenomena.

Washington, District of Columbia, installed activated carbon‐based lead mitigation filters on all water fountains/sinks in break rooms, classrooms, and health suites located in public elementary schools. To investigate the impact of these point‐of‐use filters, 12 water fountains/taps with various filter ages, with and without sediment prefilters, spread across four schools were monitored weekly from July to December 2017, along with two unfiltered sources per school (n = 8). Within the first 100 days postinstallation, filtrate from filters in schools with high influent monochloramine and no prefilter temporarily increased nitrite concentrations, with concentrations of some filters exceeding 0.4 mg/L N. Subsequent decreases in filtrate nitrite for these filters coincided with increases in live cell counts. Microbial community “fingerprints” were determined with flow cytometry. Filtered and unfiltered water fingerprints differed, indicating selective microbial growth on, and release from, the filters into the filtrate.