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The aim of this work was the application and evaluation of a mathematical model for the simulation of anaerobic hydrolysis and acid production processes. For the description of the processes involved, the Anaerobic Digestion Model ADM1 was employed. The ADM1 implementation in prefermenters is relatively easy, but the estimation of its components concentrations, kinetic parameters and stoichiometric coefficients, remains a problem to be solved. This study provides useful results for the ADM1 implementation in acid digesters design and operation. Model calibration and verification was performed using experimental data from two bench scale acid digesters operating at different temperatures (12, 20, 27 and 34 °C) and retention times (1,2, 4 and 6 days). Model sensitivity analysis illustrated that the values of pH, disintegration kinetic parameter and aceticlastic methanogenesis specific rate, as well as biomass and inert soluble COD concentrations in the primary sludge exert a significant influence on soluble COD production. Model parameters (disintegration and hydrolysis kinetic parameters and specific rate of methane production) as well as the temperature dependency of these parameters are given in this paper.

Uncontrolled landfill leachate generation portends danger to the environment and aquatic ecosystem, especially without prior treatment before discharge. The application of Al-based coagulants, such as polyaluminum chloride (PACl), has the potential of introducing Al residuals into water bodies. Therefore, an alternative natural coagulant was recommended to reduce the usage of Al-based coagulants. In this study, a coagulation–flocculation process using the combination of PACl as coagulant and Tamarindus indica seed (TiS) as coagulant aid was used in treating the landfill leachate from the Alor Pongsu Landfill Site in Malaysia. Some of the optimum operational conditions determined were the pH and dosage of the coagulant aid, and their effect was considered on parameters, such as suspended solids (SS), color, and COD, using standard jar test procedures. The combination of TiS flocculant reduced the dosage of PACl coagulant from 5,000 mg/L to 2,750 mg/L with removal efficiencies of 99.3%, 97.3%, and 67.4% for SS, color, and COD, respectively.

The main aim of this study is to investigate the simultaneous azo dye removal and bioelectricity production at sulfate reducing conditions in continuously-fed dual-chamber microbial fuel cell (MFC). Initially, optimization of sulfate reduction was performed at different sulfate concentrations (100-900 mg/L) and the constant COD of 1000 mg/L, corresponding to COD/sulfate ratio of 1.11-10, and varying HRT of 12-48h. Optimum COD/sulfate ratio and HRT was found 1.66 and 36h, respectively, corresponding to 96% COD removal, 44% sulfate removal and yielded about 24 W/m2 power density. Further, MFC was fed with azo dye containing (50-1000 mg/L) simulated wastewater to evaluate dye removal performance of sulfate reducing bacteria. Addition of azo dye slightly enhanced the power production to 26 W/m2, the highest value obtained during our study, compared to azo dye lacking study periods. Sulfate and COD removals were adversely affected at azo dye concentrations over 300 mg/L and 150 mg/L, respectively. Additionally, color removal performance of MFC was excellent however, chemical azo dye reduction out-competed with enzymatic reduction at high azo dye levels (>500 mg/L) leading to a poor sulfate (<15%) and COD (<45%) removal and recovery of azo dye reduction efficiency to 91%.

In order to study the chemical parameters of the soil after sub-irrigation with wastewater, a system was installed in one of the greenhouses of the Agricultural University of Athens. Wastewater was applied subsurface into the soil mass of the pots were used. Three treatments were used: Untreated wastewater (U), Treated wastewater (T) and tap water (W) as control. Two different types were used: Soil (a) characterized as Sandy loam and soil (b) characterized as Loamy sand. Moreover, in order to investigate the change of total Nitrogen and organic matter concentrations at the point where the emitter was placed, the soil mass was divided into two zones. The upper (zone I) and the lower one (zone II). The total nitrogen content, ammonia nitrogen (NH4-N), nitrogen nitrate (NO3-N) and the percentage of organic matter, were determined in the soil samples. Statistically significant differences (p <0, 05) were observed in the organic matter and the total N%, only for soil (b). For soil (a), organic matter percentage was increased in zone (I) (irrigation with treated wastewater at 20 cm depth). For soil (b), total N% was increased in zone (I), while nitrate and ammonium were increased in zone (II) (irrigation with untreated wastewater at 20 cm depth).