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In hydrolysis-limited anerobic systems, the key parameters describing degradation are degradability extent (f(d)), and the lumped apparent first order coefficient (k(hyd)). These are often measured in biological methane potential (BMP) tests. Using modern techniques, it should also be possible to estimate these parameters in full-scale systems, especially where inputs are dynamic. In this study, we evaluated f(d) and k(hyd) values and uncertainty based on nonlinear parameter estimation from (i) BMP tests and (ii) effluent gas and solids from two full-scale digesters fed with highly variable feed flows and concentrations (up to 6 kg COD m(-3) day(-1)). The substrate was thermally hydrolyzed activated sludge, and the inoculum for BMP tests was from the full-scale digesters. While identifiability of both parameters in the BMP tests was generally good, only f(d) could be well identified using continuous data. For k(hyd) using continuous data, normally only a lower limit could be found (upper was unbounded). In addition, parameters as estimated on different outputs (VS and gasflow) and two different digesters were consistent, with an f(d) value of 0.45-0.55, and a k(hyd) value of >5 day(-1). Gradual changes in f(d) over the 450 days could be related to upstream changes. f(d) values as estimated in BMP tests were consistent (if conservative) with continuous estimates, with a f(d) in BMP of 0.4-0.5. k(hyd) values were an order of magnitude lower (0.15-0.25 day(-1) vs. >5 day(-1)), and this translated to very poor model performance when BMP-estimated values were used in the continuous model. This means that while BMP testing may be used for project feasibility analysis, values obtained should not be used for dynamic modeling. The parameter confidence regions found were highly nonlinear, especially for continuous systems, indicating that iterative or sampling techniques are required for an estimate of real parameter uncertainty.

Solutions of sulfate have often been used as background electrolytes in the electrochemical degradation of contaminants and have been generally considered inert even when high-oxidation-power anodes such as boron-doped diamond (BDD) were employed. This study examines the role of sulfate by comparing electro-oxidation rates for seven persistent organic contaminants at BDD anodes in sulfate and inert nitrate anolytes. Sulfate yielded electro-oxidation rates 10-15 times higher for all target contaminants compared to the rates of nitrate anolyte. This electrochemical activation of sulfate was also observed at concentrations as low as 1.6 mM, which is relevant for many wastewaters. Electrolysis of diatrizoate in the presence of specific radical quenchers (tert-butanol and methanol) had a similar effect on electro-oxidation rates, illustrating a possible role of the hydroxyl radical ((•)OH) in the anodic formation of sulfate radical (SO4(•-)) species. The addition of 0.55 mM persulfate increased the electro-oxidation rate of diatrizoate in nitrate from 0.94 to 9.97 h(-1), suggesting a nonradical activation of persulfate. Overall findings indicate the formation of strong sulfate-derived oxidant species at BDD anodes when polarized at high potentials. This may have positive implications in the electro-oxidation of wastewaters containing sulfate. For example, the energy required for the 10-fold removal of diatrizoate was decreased from 45.6 to 2.44 kWh m(-3) by switching from nitrate to sulfate anolyte.