Environmental Technology

Bhattacharyya, Saurav; Chakraborty, Sudip; Datta, Siddhartha; Drioli, Enrico; Bhattacharjee, Chiranjib

doi: 10.1080/09593330.2012.733965pmid: 24191439

Potato peel is a waste biomass which can be a source of raw material for biofuel production. This biomass contains a sufficient amount of total reducing sugar (TRS), which can be extracted and further treated with microbial pathways to produce bioethanol. The extraction of TRS from potato peels by hydrolysis in dilute sulphuric acid was investigated at different acid concentrations (0.50%, 0.75% and 1% w/v) and sonication was carried out to improve the extent of sugar extraction after hydrolysis. Response surface methodology based on central composite design was used to verify the experimental data and later applied for the optimization of the main important reaction variables including amplitude (60%, 80% and 100%), cycle (0.6, 0.8 and 1.0) and treatment time (5, 10 and 15 min) for the responses of TRS extraction by acid hydrolysis and later compared with the experimental data.

Mietto, Anna; Borin, Maurizio

doi: 10.1080/09593330.2012.733967pmid: 24191440

The performance of a vertical and a horizontal subsurface flow wetland (v-SSF and h-SSF), designed for treating domestic wastewater from a single family, was investigated by monitoring total nitrogen (TN), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), total phosphorus (TP), chemical oxygen demand (COD) and the dissolved oxygen (DO) content of the influent and the effluent wastewater of each system during the first two years of operation. The growth of Phragmites australis in each system was recorded by measuring the height and observing their general conditions. The treated domestic wastewater presented similar chemical–physical characteristics in the two systems which operated in analogous environmental conditions. The median influent characteristics were: TN 81.9 mg L−1, NO3-N 0.19 mg L−1, NH4-N 33.5 mg L−1, TP 11.9 mg L−1 and COD 354.5 mg L−1. During the whole monitoring period median reductions in the v-SSF were TN 71%, NH4-N 94%, TP 27% and COD 92% whereas in the h-SSF they were TN 59%, NH4-N 21%, TP 52% and COD 70%. Internal production of NO3-N was observed, mainly in the v-SSF probably due to the difference in oxygen availability in the medium and the design of the system. DO concentration increased in the effluents in both years, with higher values measured in v-SSF than in h-SSF. The reduction performance increased in the second year, particularly in v-SSF, whereas no statistical differences were observed between spring–summer and autumn–winter periods. P. australis reached maximum development at the end of summer in both systems and maintained a stable height during autumn–winter. In h-SSF the vegetation located close to the influent showed lower growth than in the rest of the bed.

Lam, Sze-mun; Sin, Jin-chung; Abdullah, Ahmad Zuhairi; Mohamed, Abdul Rahman

doi: 10.1080/09593330.2012.736538pmid: 24191441

In the work presented here, photocatalytic systems using TiO2 and ZnO suspensions were utilized to evaluate the degradation of resorcinol (ReOH). The effects of catalyst concentration and solution pH were investigated and optimized using multivariate analysis based on response surface methodology. The results indicated that ZnO showed greater degradation and mineralization activities compared to TiO2 under optimized conditions. Using certain radical scavengers, a positive hole, together with the participation of hydroxyl radicals, were the oxidative species responsible for ReOH degradation on TiO2 whereas, the ZnO photocatalysis occurred principally via hydroxyl radicals. Some hitherto unreported pathway intermediates of ReOH degradation were identified using gas chromatography-mass spectrometry. A tentative reaction mechanism for the formation of these intermediates was proposed. Moreover, the figure-of-merit electrical energy per order was employed to estimate the electrical energy consumption.

Hamzeh, Mariam; Ouddane, Baghdad; El-daye, Mirna; Halwani, Jalal

doi: 10.1080/09593330.2012.736539pmid: 24191442

The Seine is one of the most polluted rivers in Europe with respect to potentially harmful elements. It receives effluents from the upstream Paris urban and industrial area, and also local inputs from the heavily industrialized Rouen and Le Havre regions. The present study deals with this environmental topic and the concentrations of Cd, Ni, Pb, Hg, Zn and Cu were determined in sediment cores collected in the docks basin of Rouen harbour in 2008. The intensity of metal pollution during recent decades was evaluated using an enrichment factor (EF) and a geoaccumulation index (Igeo). The results of vertical distribution showed that the metal pollution in the past is much higher than in the surface sediment. Mercury was found to be the heaviest pollutant (with Igeo and EF exceeding 4 and 20, respectively), and Cd and Pb were the second most important pollutants. A slight contamination in Ni was observed with very low Igeo values. To estimate the sediment toxicity, simultaneously extracted metals/acid volatile sulfides ratio (SEM/AVS) was calculated. Low values of the toxicity index SEM/AVS were observed in the core sediments indicating the inexistence of metal potential toxicity. Also the concentrations of these trace metals were lower than the probable effect concentration values reported as consensus-based sediment quality guidelines for fresh water ecosystems.

Güneş, Y.

doi: 10.1080/09593330.2012.736540pmid: 24191443

The aim of this work was to study the inhibition effect of boric acid and sodium borate on the treatment of boron containing synthetic wastewater by a down flow aerobic fixed bed biofilm reactor at various chemical oxygen demand (COD)/boron ratios (0.47–20.54). The inhibitory effect of boron on activated sludge was evaluated on the basis of COD removal during the experimental period. The biofilter (effective volume=2.5 L) was filled with a ring of plastic material inoculated with acclimated activated sludge. The synthetic wastewater composed of glucose, urea, KH2PO4, MgSO4, Fe2SO4, ZnSO4·7H2O, KCl, CaCl2, and di-sodium tetraborate decahydrate or boric acid (B=100–2000 mg L−1). The biological treatment of boron containing wastewater resulted in a low treatment removal rate due to the reduced microbial activity as a result of toxic effects of high boron concentrations. The decrease in the COD removal rate by the presence of either boric acid or sodium borate was practically indistinguishable. It was observed from the experiments that about 90–95% of COD removal was possible at high COD/boron ratios.

Dumont, Eric; Cabral, Flavia Da Silva; Le Cloirec, Pierre; Andrès, Yves

doi: 10.1080/09593330.2012.736691pmid: 24191444

This study aims to evaluate the feasibility of using a nutritional synthetic material (UP20) combined with fibrous peat as a packing material in treating H2S (up to 280 ppmv). Three identical laboratory-scale biofilters with different packing material configurations (peat only; peat+UP20 in a mixture; peat+UP20 in two layers) were used to determine the biofilter performances. The superficial velocity of the polluted gas on each biofilter was 65 m/h (gas flow rate 0.5 Nm3/h) corresponding to an empty bed residence time=57 s. Variations in elimination capacity, removal efficiency, temperature and pH were tracked during 111 d. A removal efficiency of 100% was obtained for loading rates up to 6 g/m3/h for the biofilter filled with 100% peat, and up to 10 g/m3/h for both biofilters using peat complemented with UP20. For higher loading rates (up to 25.5 g/m3/h), the configuration of peat-UP20 in a mixture provided the best removal efficiencies (around 80% compared to 65% for the configuration of peat-UP20 in two layers and 60% for peat only). Microbial characterization highlighted that peat is able to provide sulfide-oxidizing bacteria. Through kinetic analysis (Ottengraf and Michaelis-Menten models were applied), it appeared that the configuration peat-UP20 in two layers (80/20 v/v) did not show significant improvement compared with peat alone. Although the configuration of peat-UP20 in a mixture (80/20 v/v) offered a real advantage in improving H2S treatment, it was shown that this benefit was related to the bed configuration rather than the nutritional properties of UP20.

Machón-González, Iván; López-García, Hilario; Rodríguez-Iglesias, Jesús; Marañón-Maison, Elena; Castrillón-Peláez, Leonor; Fernández-Nava, Yolanda

doi: 10.1080/09593330.2012.737863pmid: 24191445

Numerous papers related to the estimation of wastewater parameters have used artificial neural networks. Although successful results have been reported, different problems have arisen such as overtraining, local minima and model instability. In this paper, two types of neural networks, feed-forward and neural gas, are trained to obtain a model that estimates the values of nitrates in the effluent stream of a three-step activated sludge system (two oxic and one anoxic). Placing the denitrification (anoxic) step at the head of the process can force denitrifying bacteria to use internal organic carbon. However, methanol has to be added to achieve high denitrification efficiencies in some industrial wastewaters. The aim of this paper is to compare the two networks in addition to suggesting a methodology to validate the models. The influence of the neighbourhood radius is important in the neural gas approach and must be selected correctly. Neural gas performs well due to its cooperation–competition procedure, with no problems of stability or overfitting arising in the experimental results. The neural gas model is also interesting for use as a direct plant model because of its robustness and deterministic behaviour.

Papirio, S.; Esposito, G.; Pirozzi, F.

doi: 10.1080/09593330.2012.737864pmid: 24191446

The feasibility of removing sulphate using low-density polypropylene pellets as carrier material in two lactate-fed sulphidogenic inverse fluidized-bed reactors was investigated. Two different COD/sulphate ratios and two different feed–sulphate concentrations were used for the operation of the reactors. During the 242 days of operation, the robustness of the system was studied by suddenly decreasing the feed pH to 3.00. A 10% fluidization degree was used since the carrier material adopted showed not to be adequate to attain a satisfactory immobilization of the biomass with higher fluidization degrees. This resulted in a failure of the process when the feed pH was intentionally decreased to 3.00 in reactor 2, operated with a COD/sulphate ratio of 4.00. On the contrary, when a slightly acidic feed solution was fed to reactor 2, a 97% sulphate reduction efficiency was obtained. In reactor 1, operated with a COD/sulphate ratio of 0.67 throughout the experiment, COD removal and sulphate reduction efficiencies reached the highest values of 75% and 35%, respectively. Higher efficiencies were not achieved also due to the accumulation of acetate and the most likely presence of microbial competition between sulphate reducers and other microorganisms.

López-López, Alberto; Albarrán-Rivas, María Guadalupe; Hernández-Mena, Leonel; León-Becerril, Elizabeth

doi: 10.1080/09593330.2012.743588pmid: 24191447

The lack of available technologies that assembled both the technical and economical characteristics for domestic wastewater treatment is a major problem for rural communities. In response to this issue, a technical assessment of an up-flow anaerobic filter (UAF) was carried out in the laboratory to treat domestic wastewater. Tezontle, a volcanic rock, was used as the packing media and as the support for the biofilm. It was selected due to its abundance, low cost and high porosity. The UAF assessment was based on an experimental design of two variables, hydraulic retention time (HRT) and temperature, with three and four levels of operation, respectively. Each test at HRT of 12, 18 and 24 h was carried out at temperatures of 20, 25, 30 and 35°C. Methane production rates were 32.4, 110 and 191 mL of CH4/g of chemical oxygen demand removed for HRT of 12, 18 and 24 h, respectively, at a temperature of 35°C. In order to reach a high removal of organic matter (higher than 80%) the optimum operational conditions for the UAF were HRT=24 h and T=35°C. The temperature was the determining factor for achieving the greatest removal efficiencies in the UAF.

Shokri, Mohammad; Jodat, Akbar; Modirshahla, Nasser; Behnajady, Mohammad A.

doi: 10.1080/09593330.2012.743589pmid: 24191448

In this work, silver-doped TiO2 (Ag/TiO2) nanoparticles were synthesized using a photodeposition technique. The prepared Ag/TiO2 nanoparticles were characterized using TEM, SEM, XRD, and EDX techniques. The characterization of Ag/TiO2 nanoparticles using SEM and EDX techniques revealed the dispersion of Ag metal on the surface of TiO2. The photocatalytic activity of Ag/TiO2 and bare TiO2 in the presence of ultraviolet irradiation was investigated in the removal of chloramphenicol (CAP) as an antibiotic. CAP is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria, as well as other groups of microorganisms. However, it is, in certain susceptible individuals, associated with serious toxic effects in humans including bone marrow depression, particularly severe in the form of fatal aplastic anaemia. The effects of the operational factors, such as doping content of Ag, photocatalyst dosage and calcination temperature were evaluated in the catalytic activity of Ag/TiO2. The results showed that the photocatalytic efficiency of TiO2 nanoparticles for the degradation of CAP, can be significantly improved by deposition an optimum amount of Ag nanoparticles (0.96 wt%) in the calcination temperature 300°C. It was found that 900 mg/L of Ag/TiO2 is the optimum dosage in the removal of CAP with 20 mg/L initial concentration. The highest removal efficiency of CAP (∼100%) at the optimum conditions was observed in 20 min. A mineralization study under optimum conditions showed about 88% reduction in total organic carbon after 120 min of irradiation time.