A. Gálvez

Landfill leachate treatment with microbial fuel cells; scale-up through plurality

Three Microbial Fuel Cells (MFCs) were fluidically connected in series, with a single feed-line going into the 1st column through the 2nd column and finally as a single outflow coming from the 3rd column. Provision was also made for re-circulation in a loop (the outflow from the 3rd column becoming the feed-line into the 1st column) in order to extend the hydraulic retention time (HRT) on treatment of landfill leachate. The effect of increasing the electrode surface area was also studied whilst the columns were (fluidically) connected in series. An increase in the electrode surface area from 360 to 1080 cm(2) increased the power output by 118% for C2, 151% for C3 and 264% for C1. COD and BOD(5) removal efficiencies also increased by 137% for C1, 279% for C2 and 182% for C3 and 63% for C1, 161% for C2 and 159% for C3, respectively. The system when configured into a loop was able to remove 79% of COD and 82% of BOD(5) after 4 days. These high levels of removal efficiency demonstrate the MFC systems ability to treat leachate with the added benefit of generating energy.

Effects of sulphate addition and sulphide inhibition on microbial fuel cells

The effects of adding sulphate in: (i) standard activated sludge microbial fuel cells (MFCs) and (ii) larger-scale leachate-treating columns - both as individual units and as a system connected in cascade - are reported. S-replete power output was ∼2-fold higher than that of the S-deplete MFC. Furthermore, the effects of evolved sulphide (S(2-)) inhibition were investigated. The overall decrease in power output from the sulphide inhibitor (Na(2)MoO(4)) additions was 83% for the S-replete and 90% for the S-deplete. The second phase with the leachate treating units shows an improvement of 32-86% (depended on leachate strength) in current output as a result of adding sulphate. When leachate column MFCs were connected fluidically in series, the amount of Na(2)SO(4) made available downstream was decreasing (increase in power was 99%, 40% and 12% for columns in cascade). Results demonstrated the beneficial effects of added sulphur sources to both activated sludge and leachate-treating MFCs.

Evaluation of the quality and treatability of leachate produced at a landfill connected to an urban waste composting and recovery plant at Alhendín (Granada, Spain)

Oxytetracycline (2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a major member of the tetracycline antibiotics family of which are widely administered to animals in concentrated animal feeding operations for purposes of therapeutical treatment and health protection. With the disposal of animal manure as fertilizer into agricultural land, tetracyclines enter the environment. However, tetracyclines chelate with multivalent cations and proteins, resulting in low extraction efficiencies from animal manure for tetracycline residue analysis. In this study an efficient extraction method for oxytetracycline from steer manure using methanol/water solution amended with chelating organic acid was developed for the analysis of high performance liquid chromatography. The effect of species and amount of amendment acids, shaking time, methanol/water ratio, manure weight, and repeated times of extraction was investigated. It was optimized to amend 2.5 g citric acid and 1.1 g oxalic acid with 10.0 g manure sample in a 50-ml centrifuge tube and extract with 15 ml methanol/water (9:1 in volume) by vigorously shaking for 30 min in a reciprocating shaker. After centrifugation at 11,000 rpm, supernatant is collected. Sample was extracted for a total of 3 times. The developed extraction method was further applied to extract oxytetracycline from fresh and aged cow manure, swine and poultry manure, and soil. Satisfactory recoveries ranging from (84.1 +/- 2.4) % to (102.0 +/- 3.1) % were obtained, demonstrating that the optimized extraction method is robust for oxytetracycline from different manure sample matrixes.The leachate produced at a landfill adjoining an urban waste composting and recovery plant at Alhendín (Granada, Spain) was sampled for a period of more than 3 years from February 2003 until July 2006. The main pollutant parameters (COD, BOD5, solids, nitrogen, main anions and cations, pH, Eh and conductivity) were analysed with the aim of selecting the most effective treatment for the leachate. The results obtained showed high concentrations of different pollutants with COD and BOD5 values up to 74,133 mg/L and 39,000 mg/L respectively. Seasonal changes in leachate composition were mainly attributed to differences in rainfall, temperatures, and evaporation rates. Our study classified the Alhendín landfill leachate as a partially stabilized leachate because of: (i) its management strategies (storage at artificial ponds and recirculation); (ii) the coexistence in the landfill of active and closed cells with wastes of different ages and at different decomposition phases. The leachate quality data obtained was statistically evaluated using various statistical tools. A good correlation was found between many of the parameters analysed, some of which also showed good linear regressions. Principal component analysis allowed the reduction of most of the parameters analysed to four components: Component 1 (K+, Mg2 +, FTS, VDS, VTS, Na+ and Cl−), component 2 (BOD5), component 3 (TDS, TS, FDS and conductivity) and component 4 (pH, FSS, Eh and VSS). The results obtained are valuable for the selection of the best leachate treatment option. A combination of a physicochemical treatment and a fixed film biological system is recommended for this leachate.

Efficiency of a biological aerated filter for the treatment of leachate produced at a landfill receiving non-recyclable waste

The feasibility of a biological aerated filter for the treatment of a partially stabilized leachate from a landfill receiving non-recyclable wastes was assessed in laboratory-scale experiments. Maximum COD, BOD5 and TSS removal efficiencies achievable by the biofilter as well as the optimal hydraulic and organic loading rates were determined by laboratory-scale tests in batch and continuous mode. Experiments in batch mode which lasted for 7 days showed that COD and BOD5 removal efficiencies were stabilized after the second day of operation and kept at around 56–60% and 83–97%, respectively, for the rest of the period studied. The remaining fraction (approximately 40% of the COD) was found to be composed of recalcitrant or not easily biodegradable compounds. The COD and BOD5 removal efficiencies decreased with increasing hydraulic loading rates. The plant worked under optimal conditions at hydraulic loading rates of 0.71 and 1.41 m3/m2d (hydraulic retention times of 15.95 and 7.97 h, respectively) and at COD loading rates below 14 kg COD/m3, where COD removal efficiencies were around 60%. TSS removal efficiencies were not significantly influenced by the hydraulic loading rate. The results obtained demonstrated the feasibility of a biological aerated filter for the removal of the biodegradable fraction of the organic matter contained in the leachate. However, a physicochemical process was found to be necessary as pre- or post-treatment for the removal of the recalcitrant fraction.

Characterization of the leachate produced in the closed cells of a landfill site at Alhendín (Granada, Spain)

Landfill leachates are currently one of the main problems associated with the elimination of wastes at landfills and one of the most polluting effluents. They have a complex composition, which includes dissolved organic matter, inorganic macrocomponents, heavy metals and xenobiotic organic compounds. Leachate characterization is thus an essential factor to be considered in the design of an effective treatment system. Samples were taken of the leachate produced in the closed cells of a landfill site at Alhendin (Granada, Spain) for a period of more than one year. The analyses performed included COD, BOD5, solids, ammonia, the main cations and anions, pH, redox potential, and conductivity. The results obtained show high concentrations of different pollutants. Leachate strength followed a seasonal pattern, which can be mainly attributed to variation in rainfall and temperatures as well as evaporation rates. We found that most of the parameters analyzed showed a close correlation. The principal component analysis was applied to the data with a view to evaluating the interrelationships between parameters. It was thus possible to describe the data in terms of only four components.