A study of the anaerobic digestion of wastewater from the pressing of orange peel generated inorange juice production was carried out in a laboratory-scale completely stirred tank reactor atmesophilic temperature (37
deg.gif">C). Prior to anaerobic treatment the raw wastewater was subjected tophysicochemical treatment using aluminum sulfate as a flocculant and to pH reduction using a solutionof sulfuric acid. The reactor was batch fed at COD loads of 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0g of COD. The process was very stable for all of the loads studied, with mean pH and alkalinityvalues of 7.5 and 3220 mg of CaCO
3/L, respectively. The anaerobic digestion of this substrate wasfound to follow a first-or
der kinetic mo
del, from which the specific rate constants for methaneproduction,
KG, were
determined. The
KG values
decreased consi
derably from 0.0672 to 0.0078 L/(gh) when the COD load increased from 1.5 to 5.0 g of COD, indicating an inhibition phenomenon inthe system studied. The proposed mo
del predicted the behavior of the reactor very accurately, showing
deviations of <5% between the experimental and theoretical values of methane production. Themethane yield coefficient was found to be 295 mL of CH
4 STP/g of COD removed, whereas themean bio
degradability of the substrate (TOC) was 88.2%. A first-or
der kinetic mo
del for substrate(TOC) consumption allowed
determination of the specific rate constants for substrate uptake,
KC,which also
decreased with increasing loading, confirming the above-mentioned inhibition process.Finally, the evolution of the individual volatile fatty acid concentrations (acetic, C2; propionic, C3;butyric, C4; isobutyric, iC4; valeric, C5; isovaleric, iC5; and caproic, C6) with digestion time for allloads used was also studied. The main acids generated were acetic and propionic for all loads studied,facilitating the conversion into methane.