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

Abstract

Cassava processing wastewater has a low Volatile Acidity/Total Alkalinity ratio, low buffering capacity and became quickly acidified. In this trial, dolomitic limestone was used as an alkalizing agent in an anaerobic reactor to treat cassava starch wastewater. The dolomitic limestone contained 27% CaO and 23% MgO and granulometry between 24.5 and 38.1 mm. The average Chemical Oxygen Demand of the wastewater was 13331.30 mgO2 L-1, the organic loading rates (OLR) ranged from 1.23 to 16.43 gCOD L-1 d-1 and the hydraulic retention times ranged from 10.00 to 0.80 days. The results showed that the calcium concentrations increased in the reactor effluent and the magnesium concentrations decreased as the organic loading rates increased. Ca2+ and Mg2+ concentrations were approximately 5,000 and 5.05 times greater in the sludge than in the inoculum, respectively. The average pH, Total alcalinity, Volatile Acidity and Volatile Acidity/ Total alcalinity values were 6.69, 882.54 mgCaCO3 L-1, 221.55 mgCH3COOH L-1 and 0.22, respectively. The loss of limestone mass corresponded to only 2.51% of the initial mass, after 134 days of anaerobic reactor operation. Finally, it was concluded that the limestone effectively controlled acidification through the alkalinity increased in the system.

Produção científica sobre o biogas dos resíduos do beneficiamento da mandioca no Brasil: características e abordagens

“…Among them are the comparison between the performance of inoculation with cattle and goat manure; sludge from sewage treatment plants; textile industry effluents and bacterial and microalgae cultures. There is also the co-digestion of manipueira with glycerin and the use of dolomitic limestone as an alkalizing agent (C. LARSEN et al, 2013;DE AMORIM et al, 2019;DE CARVALHO et al, 2018;PALMA et al, 2018;PERES et al, 2019).…”

Global research trends on anaerobic digestion and biogas production from cassava wastewater: a bibliometric analysis

“…In its applications, a wide range of products of economic and environmental value (e.g. methane, hydrogen, carboxylic acids) have been recovered from anaerobic treatment under different reactor configurations and operating conditions, 7,20‐22 varying key parameters for the process (temperature, pH, alkalinity) 23‐26 under distinct hydraulic retention times (HRT) 27‐29 …”

“…[17][18][19] In its applications, a wide range of products of economic and environmental value (e.g. methane, hydrogen, carboxylic acids) have been recovered from anaerobic treatment under different reactor configurations and operating conditions, 7,[20][21][22] varying key parameters for the process (temperature, pH, alkalinity) [23][24][25][26] under distinct hydraulic retention times (HRT). [27][28][29] Despite the substantial interest in carrying out further research on effluent digestion, only a few studies have performed a systematic analysis of the contributions from scientific publications on the subject.…”