Using dolomitic limestone to replace conventional alkalinization in the biodigestion of rapid acidification cassava processing wastewater

Cassava Wastewater Treatment in Fixed-Bed Reactors: Organic Matter Removal and Biogas Production

“…In addition to temperature, biomass growth may also contribute to biogas entrapment in the liquid phase. Palma et al (2018) in similar operating conditions to those adopted in this study observed that the OLR increase from 3.0 to 8.5 g.L −1 .d −1 and HRT decrease from 3.1 to 1.1 d lead to decreasing in the methane production from 0.29 to 0.18 LCH 4 .g −1 COD. According to these authors the gas volume reduction may be related to its entrapment in the reactor bed due to biofilm thickening and solids retention.…”

“…Fuess et al (2017) suggest that the biogas release to the liquid medium can be favored by adoption of the structured fixed bed, since this configuration provide increase in the empty spaces and improvement in the reactor hydrodynamic characteristics. The horizontal reactors used in this study, as well as those operated by Kunzler et al (2013) and Palma et al (2018) presented biogas production performance lower than that obtained by Araujo et al (2018) in an upflow fixed bed reactor. This reactor configuration provides more efficient mixing, improving mass transfer rates between substrate and microorganisms, promoting the release of trapped gas bubbles in the liquid and preventing the particulate matter sedimentation (Ward et al, 2008).…”

“…The high-rate reactors in place of the lagoon system have been evaluated for the cassava starch wastewater treatment, since they favor biogas valuation, with shorter hydraulic retention time (HRT) and lower area requirement. However, as these wastewaters are rapidly acidified, they demand care due to acidification risks on the anaerobic reactor (Palma et al, 2018).…”

“…Anaerobic digestion of cassava starch wastewater in a horizontal reactor without support material showed satisfactory performance, however under low organic loading rates (1.12 to 2.70 g.L −1 .d −1 ) and high HRT values (16.6 to 6.6 d) (Kuczman et al, 2011).When it is applied to reactors with smaller volumes and hydraulic retention time, the use of support material may be necessary, especially when it comes to easily acidified wastewater (Palma et al, 2018). Important aspects to be considered in selecting support materials type are: (i) ability to biomass attachment; (ii) high contact surface; (iii) low weight to do not require reactor structure increases; (iv) easiness and low obtaining costs.…”

Dolomitic limestone as an alkalizing agent for treating cassava starch wastewater in an anaerobic reactor

“…Dolomitic limestones mainly composed of Ca and Mg oxides were analysed previously by Brazilian researchers to treat wastewater from the cassava flour (Ribas & Cereda, 2004), vinasse (Oliveira Júnior et al, 2012) and cassava starch industries (Palma et al, 2018). The obtained results have indicated that Ca and Mg oxides serve as neutralizing agents and as fixed beds, mainly in rural areas.…”