Elif Soyer

Ammonia and pH Inhibition in Anaerobic Treatment of Wastewaters, Part I: Experimental

Abstract The influences of pH and ammonia on methane production in the anaerobic treatment of an acetic-propionic-butyric acid mixture in batch reactors operated at 37°C were investigated. Two independent sets of experiments were carried out using seeds from two different full-scale industrial anaerobic treatment reactors. One of the seeds (“Sludge A”) was obtained from an upflow anaerobic sludge-blanket (UASB) reactor treating the waste from a potato chips production plant. The second sludge seed (“Sludge B”) was from an expanded granular sludge-blanket (EGSB) reactor treating a corn processing waste. Experiments were carried out at four different pH values (6.8, 7.4, 7.8, 8.4) and with six different TAN (Total Ammonia Nitrogen) values (262 mg/L (control), 1000, 1500, 2000, 2500, 3000). Three vials (triple runs) were used for each pH and TAN value. The sludge seeds used in the inhibition tests were not exposed to high levels of ammonia at any stage before the tests. For each vial, cumulative methane production was monitored for a period long enough for the termination of biogas production. Although neither sludge was acclimated to ammonia, the lag-phase times were less than 2 days for Sludge A and essentially zero for Sludge B for all TAN and pH values. At certain high pH and high TAN values, however, methanogenic activity ceased within about 1–3 months; and then activity restarted and methane formation rate reached its maximum values after this period. If the experiments had not been continued following this period, this reactivation phenomenon would not have been detected.

Ammonia and pH Inhibition in Anaerobic Treatment of Wastewaters, Part II: Model Development

Abstract A new model to account for the influences of pH and ammonia on methane production in the anaerobic treatment of wastewaters is presented. The model is developed and evaluated by using two different sets of experimental data obtained using seeds from two different full-scale industrial anaerobic reactors. One of the seeds was obtained from an expanded granular sludge-blanket (EGSB) reactor treating a corn processing waste. The other seed was obtained from an upflow anaerobic sludge-blanket reactor (UASB) treating waste from a potato chips production plant. Model development is based on the data collected at four different pH values (6.8, 7.4, 7.8, 8.4) and with six different TAN (Total Ammonia Nitrogen) values (262 mg/L (control), 1000, 1500, 2000, 2500, 3000). The proposed model has a considerably more convenient form compared to other models that have been used in the literature for similar purposes. For example, the model facilitates the calculation of quantities such as the optimal pH as a function of TAN concentration, or the TAN concentration leading to 50% inhibition (TAN50) as a function of pH. High levels of correlations were achieved by the application of the proposed model to the experimental data obtained during our studies.

Characterization of apricot stone shells as a rapid filter medium

Two different size fractions of crushed apricot stone shells were prepared and characterized to investigate the use of this material in granular filters. Density, equivalent diameter, percent water absorption, sphericity, and bed porosity were determined to characterize the particles. Two different sets of leaching tests were performed to quantify the amount of organic matter released from apricot stone medium in water: (i) the amount of organic carbon that passes to water when the particles and water are contacted in a well-mixed batch container, and (ii) the organic carbon found in the filtrate of a fixed bed of apricot stone particles. The Ives’ filterability test was employed to evaluate the effectiveness of removing particulates from a surface water as a function of apricot stone fraction size and coagulant dosage.