A. Lopez

Combined chemical and biological degradation of tannery wastewater by a periodic submerged filter (SBBR).

The paper reports on the results of an investigation aimed to evaluate the performances of an innovative tannery wastewater process based on the combining biological degradation, carried out in a sequencing batch biofilm reactor, with chemical oxidation, performed by ozone. The combined treatment was carried out at the laboratory scale on real primary effluent coming from a centralised plant treating the wastewater from a large tanning district in Northern Italy. SBBR performances with and without ozonation were compared resulting to be very satisfactory only in the latter instance where recorded COD, NH4-N and TSS average removals were 97%, 98% and 99.9%, respectively. Such efficiencies correspond to specific concentrations in treated effluent well below the limit values fixed by the in-force Italian regulations. Furthermore, it was proved that the combined process is characterised by a very low sludge production. In fact, the measured specific sludge production (0.03 kg TSS/kg COD(removed)) resulted unexpectedly much more lower than the value reported for conventional biological systems (i.e., 0.3-0.5 kg TSS/kg COD(removed)).

Removal of Organics and Degradation Products from Industrial Wastewater by a Membrane Bioreactor Integrated with Ozone or UV/H2O2 Treatment

The treatment of a pharmaceutical wastewater resulting from the production of an antibacterial drug (nalidixic acid) was investigated employing a membrane bioreactor (MBR) integrated with either ozonation or UV/H(2)O(2) process. This was achieved by placing chemical oxidation in the recirculation stream of the MBR. A conventional configuration with chemical oxidation as polishing for the MBR effluent was also tested as a reference. The synergistic effect of MBR when integrated with chemical oxidation was assessed by monitoring (i) the main wastewater characteristics, (ii) the concentration of nalidixic acid, (iii) the 48 organics identified in the raw wastewater and (iv) the 55 degradation products identified during wastewater treatment. Results showed that MBR integration with ozonation or UV/H(2)O(2) did not cause relevant drawbacks to both biological and filtration processes, with COD removal rates in the range 85-95%. Nalidixic acid passed undegraded through the MBR and was completely removed in the chemical oxidation step. Although the polishing configuration appeared to give better performances than the integrated system in removing 15 out of 48 secondary organics while similar removals were obtained for 19 other compounds. The benefit of the integrated system was however evident for the removal of the degradation products. Indeed, the integrated system allowed higher removals for 34 out of 55 degradation products while for only 4 compounds the polishing configuration gave better performance. Overall, results showed the effectiveness of the integrated treatment with both ozone and UV/H(2)O(2).

Granular biomass structure and population dynamics in Sequencing Batch Biofilter Granular Reactor (SBBGR)

The aim of this paper is to study the microbial and structural changes occurring during the transition from flocculent (used as inoculum) to biofilm and granular sludge in a Sequencing Batch Biofilter Granular Reactor (SBBGR). SBBGR is a new and promising technology characterised by low sludge production (5-6 times lower than in conventional treatment plants), high biomass concentration (up to 35 g TSS/L(bed)), high COD conversion capacity, high effluent quality and operation flexibility. Molecular in situ detection methods and microscopy staining procedures were employed in combination with the traditional measurements (i.e., oxygen uptake rate, COD removal efficiency) to evaluate the microbial activity and composition of the granular biomass. The granules structure was investigated by electron scanning microscopy, phase contrast analysis of granule sections and specific extracellular polymeric substances (EPS) stainings. Evident changes in biomass composition was observed during the shift from activated to granular sludge while a stable presence of active bacterial populations (mainly Proteobacteria) was found within mature granules.

Degradation of herbicides (ametryn and isoproturon) during water disinfection by means of two oxidants (hypochlorite and chlorine dioxide)

The paper reports the results of an investigation aimed to find out the number and the chemical structures of byproducts which form during the reactions occurring in aqueous solution between two very common disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO 2 ), and two herbicides widely used in agriculture and frequently found in groundwaters: ametryn and isoproturon. Under controlled experimental conditions [T=20°C, pH=7, reaction-time = 48h, herbicide/disinfectant molar ratios: 0.05 and 0.05×10 −2 ], ametryn reactions with chlorine dioxide much slower than with sodium hypochlorite, whereas the opposite trend has been observed for isoproturon. In any case, however, the higher the reagents concentration the faster the reactions. As for reaction byproducts, they have been detected by HPLC and identified by HPLC-MS. In particular, ametryn (R-S-CH 3 ) reaction with NaClO gives rise to the consecutive formation of four derivatives: the sulphoxide (R-SO-CH 3 ), the sulphone (R-SO 2 -CH 3 ), the sulphonate ester (R-O-SO 2 -CH 3 ) and its hydrolysis product (R-OH). Within the fixed reaction time (48h), ametryn reaction with ClO 2 forms only the sulphoxide derivative (R-SO-CH 3 ). As for isoproturon, it reacts with both oxidants forming aromatic-ring substituted derivatives. In particular, during the reactions with NaClO and ClO 2 , four and two (chlorinated and/or hydroxylated) derivatives are respectively formed.

Prometryne oxidation by sodium hypochlorite in aqueous solution: kinetics and mechanism.

The reaction of the herbicide prometryne (C 9 H 16 N 5 -S-CH 3 ) with sodium hypochlorite has been investigated from the kinetic and mechanistic stand point. Under the fixed experimental conditions : pH = 7, T = 25 °C, [NaClO]/[substrate] = (10 -3 M)/(10 -5 M), prometryne oxidation takes place according to the following pathway : R-S-CH 3 (P) → R-SO-CH 3 (a) → R-SO 2 -CH 3 (b) → R-O.SO 2 -CH 3 (x) → R-OH (c), where R stands for C 9 H 16 N 5 , i.e., the substituted triazine ring of prometryne and (x) is an unexpected intermediate never previously detected nor identified. After having synthesized the pure intermediates (a), (b), and (x), the values of the pseudo-first-order kinetic constants of the first three steps were experimentally obtained : [k 1 = (0.64 ± 0.03) s -1 , k 2 = (1.81 ± 0.05) x 10 -3 s -1 , k 3 = (1.50 ± 0.03) x 10 -4 s -1 ]. As for k 4 , its value [(2.5 ± 0.2) x 10 -5 s -1 ] has been calculated indirectly on the basis of the kinetic theory concerning consecutive reactions. All the steps were pseudo-first-order reactions with respect to their specific substrate. The effect of pH on the hydrolysis of (b) [(b)→(c)], in the absence of NaClO, has been also assessed to better elucidate the mechanism of the overall pathway.

Removal of endocrine disrupter compounds from municipal wastewater by an innovative biological technology.

The removal of selected endocrine disrupter compounds (EDCs), namely estrone(E1), 17beta-estradiol (E2), 17alpha-ethynylestradiol (EE2), bisphenol A (BPA) and 4-tert-octylphenol (4t-OP) from municipal wastewater was investigated using a sequencing batch biofilter granular reactor (SBBGR), a new system for biological treatment based on aerobic granular biomass. This new biological treatment is characterized by high biomass concentration (up to 40 g/L), high sludge retention times (up to 6 months) and low sludge production (i.e., an order of magnitude lower than commonly reported for conventional biological technologies). The investigation was carried out comparing a demonstration SBBGR system with a conventional full-scale activated sludge process. Results showed that the SBBGR performed better than a conventional activated sludge process in removing E1, E2, BPA and 4t-OP. In fact, the average removal percentages of the above mentioned EDCs, obtained during a four month operating period, were 62.2, 68, 91.8, 77.9% and 56.4, 36.3, 71.3, 64.6% for the demonstrative SBBGR system and the conventional activated sludge process of the municipal sewage treatment plant, respectively.

Membrane filtration of municipal wastewater effluents for implementing agricultural reuse in southern Italy.

Membrane filtration was investigated at field scale in order to assess its effectiveness for reusing municipal effluents in agriculture. The study was started on April 2002 and ended on September 2007, as part of a national R&D project (AQUATEC). Preliminary results, which we already reported elsewhere, concerned the first two project years while this paper refers to the subsequent period. Three different crops (processing tomato, fennel and lettuce) were grown in rotation at a test field located in Apulia (Southern Italy) and irrigated with membrane filtered municipal secondary effluents. The quality of the reclaimed water was monitored chemically and microbiologically, and compared with conventional water pumped from a local well. Both water sources were used in parallel for irrigating two plots of the test field. The results showed that the microbiological quality of the treated wastewater was comparable to or even higher than that of the conventional source. Protozoan (oo)cysts were experimentally identified as effective indicators of possible failures of the filtration system. Moreover, long term heavy metals accumulation trends were monitored in soil and crops, showing that despite some lead and copper accumulation in the soil, no measurable increase of these metals was observed in the edible parts of the crops.

Municipal wastewater treatment by a periodic biofilter with granular biomass.

The paper reports the results obtained during an experimental campaign aimed at transferring aerobic granulation to a demonstrative SBBGR system (i.e., a submerged biofilter that operates in a fill and draw mode) for the treatment of municipal wastewater by financial support of the European Commission, within the framework of Life-Environment Programme (PERBIOF Project; www.perbiof-europe.com). The results show that following the generation of granular biomass during the start-up period, the SBBGR was able to remove 80-90% of COD, total suspended solids and ammonia occurring in primary effluent from a municipal wastewater treatment plant even when the minimum hydraulic residence time (i.e., 4 h) was investigated. The process was characterised by a sludge production almost one magnitude order lower than commonly reported for conventional treatment plants. The granular biomass was characterised by a high density (i.e., 150 gTSS/L(biomass)) that allowed a biomass concentration as high as 35 kgTSS/m(3)(bed) to be achieved. Proteobacteria were found as main microbial components of the granular biomass by applying Fluorescence In Situ Hybridization (FISH). No significant changes in microbial composition were observed during reactor operation.