Abstract
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.
Highlights
In Brazil, starch industries generate 2.6 m3 of root wash water and 3.6 m3 of water of starch extraction per ton of processed manioc (Pinto & Cabello, 2011)
The calcium concentration in the reactor effluent was higher than the concentration of this element in the reactor affluent, while the magnesium concentration was lower in the effluent than in the reactor affluent
The Ca2+ content significantly increased from organic loading rate 1.54 gCOD L-1 d-1 and remained constant until organic loading rate of 8.11 gCOD L-1 d-1 was reached, which corresponded with the point at which the Ca content of the reactor effluent began to decrease
Summary
In Brazil, starch industries generate 2.6 m3 of root wash water and 3.6 m3 of water of starch extraction per ton of processed manioc (Pinto & Cabello, 2011). The physicochemical characterization of the wastewater of cassava industry may vary depending on the variety of the roots and starch extraction process (Camili & Cabello, 2008). Starch production generates wastewater with organic matter concentrations of up to 15000 mg L-1 (Kuczman et al, 2011). Cassava processing wastewater requires treatment because it is a pollutant. Anaerobic reactors are able to tolerate high organic loading and offer the possibility of operating with high solids retention times (Aquino & Chernicharo, 2005). PH values below 6.0 and above 8.3 must be avoided in order to prevent the inhibition of methanogenic Achaea (Chernicharo, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
