E. Rolle

The Biological Aerated Filter (BAF) as alternative treatment for domestic sewage. Optimization of plant performance.

The aim of the present study was to investigate the suitability of a Biological Aerated Filter (BAF) plant as an alternative process or an upgrading step for the treatment of domestic wastewater from the city of Rome, Italy. The results obtained through a three years experimental activity on a pilot-scale BAF plant fed with real wastewater showed high process efficiencies and stable performance for both carbon and ammonia oxidation. The effluent quality met, on average basis, 68 mg/L total COD (COD(tot)), 37 mg/L Total Suspended Solids (TSS), 3.3mg/L ammonia-nitrogen (NH(4)(+)-N) and 21.1mg/L nitrate-nitrogen (NO(3)(-)-N). Despite the good performance, the high content of suspended solids in the influent stream caused filter bed clogging and frequent backwashing operations were required. Therefore, in the last part of the experimental activity a pre-treatment step was adopted prior to the biological step, consisting of chemical precipitation by lime addition. The influent quality parameters were consequently modified; for instance the particulate matter content was reduced by about 73%. The process efficiency of both ammonia and organic carbon oxidation did not modify appreciably; however, a beneficial effect was obtained on the frequency of the backwashing phase, which could be reduced by half. Since the new combined chemical-biological system demonstrated to be a valid alternative to the activated sludge treatment plant, a modeling activity was finally performed with the aim of evaluating the design parameters of a full-scale BAF plant fed with the same pre-treated wastewater as used in the experimental activity. The results of this phase are also herewith presented and discussed.

Remediation of chlorophenol- and phenol-contaminated groundwater by a sequencing batch biofilm reactor

The paper describes the results of an investigation aimed at evaluating suitability of a lab-scale Sequencing Batch Biofilm Reactor (SBBR) for the remediation of groundwater contaminated by phenol (P) and 2-chlorophenol (2-CP). Kinetics of compound degradation was determined along the bed height in the absence and in presence of effluent recirculation, and with different influent composition (compounds fed separately or in combination in the same stream). SBBR performances with and without recirculation were very satisfactory for all the influent compositions: the system showed 99% removal efficiencies for both phenol and 2-CP and their complete removal was always achieved far before the end of react. In the presence of recirculation, the concentration gradient established during fill was rapidly eliminated and an even biomass distribution along the bed height was formed. Consequently, an acceleration of the elimination process was observed, particularly for phenol that was mostly removed in the first hour of the cycle. When the compounds were fed simultaneously, 2-CP removal kinetics improved probably due to cometabolism. The adsorption phenomena of the toxic compounds on the packing material were studied also, showing about 50% COD removal after 7 hours contact time.

Application of excess activated sludge ozonation in an SBR Plant. Effects on substrate fractioning and solids production

This paper provides new insights on the application of the ozonation process for the reduction of the activated sludge production in a sequencing batch reactor (SBR). The study was performed in two identical lab-scale SBRs plant, one for experimental activities (Exp SBR) and one used as control (Control SBR), both fed with domestic sewage. A fraction of the activated sludge collected from the Exp SBR at the end of the aerobic react phase was periodically subjected to ozonation for 30 minutes at three different specific dosages (0.05, 0.07 and 0.37 g O(3)/gSS) and then recirculated before the beginning of the following cycle.Recirculation of the ozonated sludge to the Exp SBR did not appreciably affect the efficiency of the biological nitrogen and carbon removal processes. Nonetheless, an improvement of the denitrification kinetic was observed. Mixed liquor volatile and suspended solids (MLSS and MLVSS, respectively) concentrations in the reactor decreased significantly with time for long term application of the ozonation treatment. Kinetic batch tests on unstressed sludge taken from Control SBR indicated that the different oxidant dosages (0.05, 0.07 and 0.37 g O(3)/gSS) and durations of the ozonation process (10, 20 and 30 minutes) used remarkably affected chemical oxygen demand (COD) and organic nitrogen fractioning. In particular, soluble and biodegradable fractions seemed to be higher at lower dosage and longer contact time.

Assessing anaerobic biodegradability of polymeric materials under acidogenic or methanogenic conditions

The anaerobic degradation of polymeric materials was studied in batch tests by determination of the conversion yields to volatile fatty acids (acidogenesis) or to methane (methanogenesis). By both methods, filter paper, polyhydroxybutyrate (PHB), and two starch‐containing plastic materials (low and high starch contents) were examined with glucose and polyethylene as positive and negative control, respectively. Conversion yields were expressed in terms of Theoretical Oxygen Demand (ThOD). Methanogenesis and acidogenesis are basically analogous with respect to the final conversion yield. PHB and filter paper show a high conversion yield, comparable to glucose. The material with low amount of starch additive presents very low conversion yields, whereas the starch‐based material is significantly degraded, even if in percentages not higher than starch content. Acidogenic tests are always quicker than methanogenic tests. The rate determining step is generally the hydrolysis of the particulate substrate in the c...