The biological removal of hydrogen sulfide at low concentration (<120 ppmv) was studied in a laboratory-scale biofilter packed with sugarcane bagasse and inoculated with a sulfur-oxidizing bacterial consortium isolated from activated sludge from a wastewater treatment plant (WWTP). Inlet loads from 1.31 to 20.2 g Sm(-3) h(-1) were supplied to the biofilter, and empty bed residence times (EBRTs) of 30, 20 and 10 s were tested. In all cases, the removal efficiency was greater than 99%. Two methods for the pH control were tested: increasing the phosphate buffer capacity of the mineral medium (method I), and a new method, which involves the addition of solid CaCO(3) to the bagasse at the upper inlet of the biofilter (method II). For method I, pH increased gradually along the bed (from the bottom to the top), from a constant value of 3.0 to 7.0. For method II, pH was constant (2.4 ± 0.8) along the bed, and then a steep increase of pH was observed at the top to 7.1. We suggest the use of CaCO(3) instead of phosphate buffer because the former is less expensive, it is a simple method and the results obtained with the two methods are similar.

This work deals with acid hydrolysis of bagasse in just one step and in a modified step using concentrated sulphuric acid. The study analysed the influence of three independent variables on the single-step process (reaction time, solid percentage of bagasse and temperature). The highest conversion obtained in single-step hydrolysis was 87.65% fermentative sugars, using 70% sulphuric acid with 2% solids at 50ºC for 1 hour. The modified process was carried out based on these results; 97.5% maximum conversion of fermentative sugars was achieved using 30% acid dilution. Concentrated sulphuric acid single-stage hydrolysis of bagasse and in a single modified stage were subjected to technical-economic analysis. Starting from the results obtained experimentally of the process at laboratory level and elevated to a possible plant with a capacity to produce 800 HL alcohol/day. VAN and PRD indices indicated that single-stage concentrated acid hydrolysis Variant 1) having 8,310,659.27 VAN and 3 year PRD was more feasible than the modified process (variant 2) having 3,293,318.69 VAN and 7 year PRD.