Digestion Of Olive Mill Wastewater Research Articles

Anaerobic digestion of olive mill wastewaters in fully mixed reactors and in fixed film reactors

Calcium hydroxide precipitates phenolic compounds and long chain fatty acids toxic to methanogenic bacteria, and improves the total alkalinity; it is therfore better for the adjustment of the pH of olive mill wastewaters (OMW) than sodium hydroxide. The fully mixed reactors are adequate for volatile fatty acid production from OMW, although an anaerobic filter is advisable for methanogenesis. The anaerobic filter filled with a clay media matrix which is less porous and has a larger specific area than PVC, gives a quick start-up and a satisfactory performance.

Kinetics of methane production from olive mill wastewater

A kinetic study on the anaerobic digestion of olive mill wastewater (OMW) was carried out in a semicontinuous, well-stirred fermenter with microorganisms immobilized on clayey supports. Substrate concentrations equal to or higher than 3·5 g COD/litre within the reactor resulted in a methane production rate that was first-order with respect to biodegradable substrate concentration. The apparent rate constant was proportional to the VSS concentration and varied slightly with the nature of the support. The yield coefficient, Y p/s, was 0.26 litres CH 4 STP/g COD irrespective of the support used.

Effects of agitation and pretreatment on the batch anaerobic digestion of olive mil

The anaerobic digestion of olive mill wastewaters (OMW) can be carried out only on a diluted substrate because aromatic compounds and lipids are toxic for methanogenic bacteria. Agitation decreases methane formation in anaerobic digestion of unmodified OMW. Acidified OMW is less toxic than is raw waste. Pretreatment of OMW by fermentation with Aspergillus niger decreases the toxicity for methanogenic bacteria and facilitates anaerobic digestion. Moreover, agitation did not affect gas production.

Comparison between anaerobic filter and anaerobic contact process for fermented olive mill wastewaters

Abstract During the anaerobic digestion of olive mill wastewaters (OMW) prefermented by aerobic growth with Aspergillus niger , a stationary state was reached more quickly with the anaerobic contact process than with an anaerobic filter, but was more stable with the anaerobic filter. The daily methane production and COD removal recorded with the anaerobic filter were greated than those obtained in the anaerobic contact reactor. The anaerobic filter yielded a biogas with a higher percentage of methane, and effluent with a lower volatile fatty acid and volatile solid content than the anaerobic contact. The immobilizing of VS in an anaerobic filter fermenter is a means of reducing the inhibition of methanogenic bacteria by the residual phenolic compounds present in prefermented OMW. A yield of 0·15 and 0·33 litres methane/g COD removed was obtained with the anaerobic contact and anaerobic filter reactors, respectively. Additional advantages of fixed film over contact fermenters include the elimination of mechanical mixing and sludge settling and return.

Influence of immobilization supports on the kinetic constants of anaerobic purification of olive mill wastewater

Studies are made of the anaerobic digestion of olive mill wastewater (OMW) using bioreactors housing various suspended supports for immobilization of the microorganisms. The OMW inhibited the digestion as the digester loadings increased, and the support medium affected the inhibition. By applying the international Time Series Processor (TSP) computer program, version 4·0 D (Stanford, CA, USA), through the Roediger equation G = G mm[1 − exp ( − K obst)], to the resultsobtained the G m and K obs values were calculated. From the G m values was then calculated the coefficient of yield for each support. The results show the influence of the different supports used to immobilize the bacteria on the biomethanation of OMW; this is of relevance to the development of fluidized-bed processes.