The objective of this research was to characterize the anaerobic biodegradability of municipal refuse components by measuring methane yields, the extent of cellulose and hemicellulose decomposition, and leachate toxicity. Tests were conducted in quadruplicate in 2-L reactors operated to obtain maximum yields. Measured methane yields for grass, leaves, branches, food waste, coated paper, old newsprint, old corrugated containers, and office paper were 144.4, 30.6, 62.6, 300.7, 84.4, 74.3, 152.3, and 217.3 mL of CH4/dry g, respectively. Although, as a general trend, the methane yield increased as the cellulose plus hemicellulose content increased, confounding factors precluded establishing a quantitative relationship. Similarly, the degree of lignification of a particular component was not a good predictor of the extent of biodegradation. With the exception of food waste, leachate from the decomposition of refuse components was not toxic as measured by using an anaerobic toxicity assay.

The objective of this study was to characterize the anaerobic biodegradation of food waste, including its methane potential and the anaerobic toxicity of leachate associated with food waste decomposition. Biodegradation experiments were conducted in 2.2litre reactors and were seeded with well-decomposed refuse. Despite pH neutralization, reactors seeded with 30% old refuse failed to undergo methanogenesis. Food waste in a second set of reactors, containing 70% seed, produced 300.7 ml CH 4 dry g -1 . Leachate toxicity was evaluated by a modified anaerobic toxicity assay (ATA). The results of ATAs were typically consistent with the methane production behavior of the reactors. However, the toxicity observed in the ATA test could not be simulated with synthetic leachate containing high concentrations of carboxylic acids and sodium. Tests with 20, 5, 15 and 12 g 1 ' of acetate, propionate, butyrate and sodium, respectively, suggested that high concentrations of butyric acid and sodium inhibited the onset of methane production but that refuse micro-organisms could acchmatize to these concentrations within 5-10 days. The refuse ecosystem was shown to tolerate higher concentrations of undissociated carboxylic acids than previously reported for anaerobic digesters. © 1997 ISWA

No abstract

The Fundão Dam breached on 5 November 2015 (the “Event”), resulting in the release of tailings, water, scoured sediment and/or soil, and other debris to downstream watercourses. Statistical analyses using historical and recent water quality measurements were conducted to assess the extent to which water quality in the Rio Doce was recovering to baseline conditions. A review of station‐ and/or parameter‐specific water quality time series in the Rio Doce revealed two challenges: pre‐Event data imbalance and seasonality. Due to the combined effects of these two factors, data gathered from Rio Doce water quality stations before the Event likely underestimated concentration ranges and limited the usefulness of common recovery assessment techniques such as times series and water quality standard exceedance analyses. These challenges were addressed by calculating quarterly and watershed‐specific river‐to‐tributary ratios. R code was used to produce spatiotemporal time series for 44 investigated parameters that were measured both before and after the Event. The water quality recovery durations shown by the parameter‐ and/or region‐specific river‐to‐tributary ratio time series indicated that (a) turbidity provides the most conservative measure for water quality recovery; (b) chemical parameters associated with the tailings, like manganese and iron recovered faster than turbidity; and (c) other investigated parameters unrelated to the tailings showed either no discernable impact or rapid recovery after the Event. The resulting parameter‐ and/or region‐specific river‐to‐tributary ratio time series provided reliable and quantifiable estimates of water quality recovery durations. The water quality in the region furthest from Fundão Dam, in Espírito Santo, recovered one year after the Event, while water quality in the closest region to Fundão Dam, upstream of Risoleta Neves (Candonga) Dam, recovered 4.2 years after the Event. Integr Environ Assess Manag 2023;00:1–13. © 2023 Newfields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The Fundão Dam breach impacted the Rio Doce's estuarine and marine environments with tailings, water, scoured soil/sediments, and other debris. Time series and standard exceedance analyses are typically used to assess water quality recovery to baseline conditions after deteriorating water quality events. In the absence of historical measurements, impacts to water quality from the Fundão event were compared to measurements of nearby rivers. Similar river systems with available water quality measurements were grouped into affected and unaffected estuarine and marine waters. Statistical and temporal comparisons of marine waters unaffected by the Rio Doce to those affected by the Rio Doce were evaluated for systematic differences. Multivariate statistical techniques were also used to assess water quality differences. Our results demonstrate that the Fundão Dam breach had a short‐term water quality impact on marine waters near the Rio Doce mouth. Principal component and comparative time series analyses clearly demonstrated this impact during the 2015/16 and 2016/17 wet seasons. The ephemeral effects of the breach, however, did not compromise marine water quality. Exceedances of CONAMA standards for metals remained either at zero or at very low levels during the impacted period (less than 5.7%). Before the start of the next wet season in October 2017, water quality impacts from the Event were statistically indistinguishable from unaffected marine waters, indicating recovery to baseline conditions.