Ozonation catalyzed by iron- and/or manganese-supported granular activated carbons for the treatment of phenol.

Iron- and/or manganese-supported catalysts on granular activated carbons (Fe and/or Mn/GACs) were prepared, and their catalytic activities were evaluated by using them to treat phenol and secondary petrochemical effluent via ozonation. The presence of Fe and/or Mn/GACs significantly improved the degradation and degree of phenol mineralization. Changes in dissolved ozone concentrations and the effects of carbonate and tert-butyl alcohol (TBA) indicated that the prepared catalyst enhanced the decomposition of ozone into hydroxyl radicals (·OH), which was determined to be a key factor in catalyzing the ozonation of phenol.

[Effects of COD/TN and HRT(s) on nutrients removal by an alternating anoxic/oxic CAST].

The effects of different COD/TN and HRT(s) (hydraulic retention time of select) on nutrients removal were investigated by using an alternating anoxic/oxic CAST (cyclic activated sludge technology) fed with municipal wastewater. The results showed that various COD/TN and HRT(s) had a bigger influence on the nitrogen removal efficiency rather than the COD removal efficiency. As the influent C/N ratios were about 2.

Effect of influent nutrient ratios and temperature on simultaneous phosphorus and nitrogen removal in a step-feed CAST.

A step-feed cyclic activated sludge technology (CAST) with a working volume of 72 L treating real municipal wastewater was operated to examine the effect of varying ratios of influent COD/TN and COD/P on the nutrient removal. With the increased COD/P and COD/TN, the phosphorus and nitrogen removals exhibited an upward trend. The TN removals had a positive linear correlation with the phosphorus removal efficiencies, mainly because the presence of nitrate in the anaerobic zone negatively affected the phosphorus release thus the nitrogen removal process took priority over the phosphorus removal process to utilize the limited carbon source in the influent in step-feed CAST where simultaneous removals of nitrogen and phosphorus were achieved.

Biological nitrogen removal in a step-feed CAST with real-time control treating municipal wastewater.

The performance of a 18 L step-feed cyclic activated sludge technology (CAST) combined with real-time control treating real municipal wastewater was evaluated. The operation strategies employed pH and oxidation reduction potential (ORP) as on-line control parameters, which can control the durations of oxic and anoxic phases flexibly. The obtained results showed that the studied process had achieved advanced and enhanced nitrogen removal by several phases of consecutive oxic/anoxic periods.

Denitrifying phosphorus removal in a step-feed CAST with alternating anoxic-oxic operational strategy.

A bench-scale cyclic activated sludge technology (CAST) was operated to study the biological phosphorus removal performance and a series of batch tests was carried out to demonstrate the accumulation of denitrifying polyphosphate-accumulating organisms (DNPAOs) in CAST system. Under all operating conditions, step-feed CAST with enough carbon sources in influent had the highest nitrogen and phosphorus removal efficiency as well as good sludge settling performance. The average removal rate of COD, NH4+-N, PO4(3-)-P and total nitrogen (TN) was 88.