Determination of granule size distribution in a UASB reactor

Granular sludge is the key factor for an efficient operation of an upflow anaerobic sludge blanket (UASB) reactor. In order to monitor the granularity of anaerobic sludge, the determination of the granule size distribution is of vital importance. For this reason, several techniques have been proposed; however, they are either tedious, imprecise or expensive and hardly applicable in full-scale treatment plants. There was then the need for a simple and low-cost technique. This technique involves the determination of the settling velocities of a sludge sample and of extrapolating the corresponding diameters using a mathematical algorithm. In the proposed algorithm, the granules density was calculated, the flow regime was examined and finally the granule size distribution was obtained. Two very important correlations were suggested by the experimental results. The granule density and diameter were strongly correlated with the VSS/TSS ratio.     

Dynamic Modeling of the Ratio Volatile Fatty Acids/Bicarbonate Alkalinity in a UASB Reactor for Potato Processing Wastewater Treatment

In this work, dynamic mathematical model for the prediction of the operational parameter volatile fatty acids/bicarbonate alkalinity (VFA/ALK) in a UASB reactor was developed. The dynamic modeling technique was applied successfully to a two-year data record from an industrial wastewater treatment plant of a potato processing industry. The technique used included regression analysis by residuals. Seventeen parameters were examined including the following: wastewater's flow rate, reactor's temperature and pH, total and soluble influent COD, wastewater's temperature and pH, total and soluble effluent COD, volatile fatty acids, alkalinity, biogas production rate and each parameter with a time lag of up to 10 days. Finally, after all parameters and all time lag trials the best fitted model was developed. The model's adequacy was checked by χ² test for a data record of the same UASB reactor but at a different time period and proved to be satisfactory. Additionally, the model's ability to predict and to control the plant's operation via VFA/ALK was examined. Through this model, in contrary to steady state models, various aspects of the process can be enlighten, such as the fact that the hydrolysis of starch requires at least a resident time of seven days.     

Ethanol production from potato peel waste (PPW)

Considerable concern is caused by the problem of potato peel waste (PPW) to potato industries in Europe. An integrated, environmentally-friendly solution is yet to be found and is currently undergoing investigation. Potato peel is a zero value waste produced by potato processing plants. However, bio-ethanol produced from potato wastes has a large potential market. If Federal Government regulations are adopted in light of the Kyoto agreement, the mandatory blending of bio-ethanol with traditional gasoline in amounts up to 10% will result in a demand for large quantities of bio-ethanol. PPW contain sufficient quantities of starch, cellulose, hemicellulose and fermentable sugars to warrant use as an ethanol feedstock. In the present study, a number of batches of PPW were hydrolyzed with various enzymes and/or acid, and fermented by Saccharomyces cerevisae var. bayanus to determine fermentability and ethanol production. Enzymatic hydrolysis with a combination of three enzymes, released 18.5 g L^?1 reducing sugar and produced 7.6 g L^?1 of ethanol after fermentation. The results demonstrate that PPW, a by-product of the potato industry features a high potential for ethanol production.     

Electrochemical detoxification of four phosphorothioate obsolete pesticides stocks

The phosphorothioate pesticides are widely used for crop production and fruit tree treatment, but their disposal causes serious environmental problems. Four commercial phosphorothioate pesticides (Demeton-S-methyl, Metamidophos, Fenthion and Diazinon) were treated by an electrolysis system using Ti/Pt as anode and stainless steel 304 as cathode. A number of experiments were run in a laboratory scale pilot plant and the results are presented. For Fenthion the achieved reduction was over 60%, while for Demeton-S-methyl, Metamidophos and Diazinon was more than 50%. Diazinon had the lowest energy demand. The COD/BOD5 ratio was improved considerably after electrolysis for all four pesticides examined. As a conclusion, electrochemical oxidation could be used as a pretreatment method of the pesticides detoxification.     

Detoxification of tannery waste liquors with an electrolysis system

This paper describes an electrochemical treatment and detoxification of tannery waste liquors (TWL). In this technique, TWL was passed through an electrolytic cell using a Ti/Pt anode and a stainless steel 304 cathode. Owing to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) the organic and inorganic pollutants (ammonia, sulfides and chromium) were wet oxidized to carbon dioxide, nitrogen oxides and sulfur dioxide. In addition, chromium was precipitated as Cr(2)(SO(4))(3). Experiments were run in a batch, laboratory-scale, pilot-plant, and the results are reported herein. After 30 min and 3 h of electrolysis at 0.26 A cm(-2), 45 degrees C and pH 9, total chemical oxygen demand (COD) was reduced by 52 and 83% and biochemical oxygen demand (BOD(5)) was reduced by 35 and 66%, respectively. Additionally, total suspended solids (TSS) were reduced by 8.6 and 26%, total phenolic compounds were reduced by 95.6 and 99.4%. Ammonia, sulfides and soluble chromium were reduced by 100% in both cases, while the mean anode efficiency was 81 g h(-1) A(-1) m(-2) and 1.9 g h(-1) A(-1) m(-2). Also, the mean energy consumption was 4.8 kwh kg(-1) of COD reduced and 200 kwh kg(-1) of COD reduced for 0.5 and 3 h, respectively. These results strongly indicate that this electrolytic method of total oxidation of TWL cannot be cost effective for wide use. However, it can be used as an effective pretreatment stage for detoxification of the wastewater, owing to great efficiency especially with respect to COD and toxicity (phenolics) reduction.