Comparison of two anaerobic coupled systems for biomethanization of the organic fraction of municipal solid wastes

Two lab-scale mesophilic systems for the anaerobic digestion of the organic fraction of municipal solid wastes (OFMSW) were compared. One system (RE-RE) consisted of two coupled reactors packed with OFMSW and the other (UASB-RE) consisted of an upflow anaerobic sludge blanket reactor (UASB) coupled to a packed reactor For the start-up phase, both leading reactors RE 1.1 and UASB 2.1 were inoculated with a mixture of non-anaerobic inocula and worked with leachate and effluent full recirculation. Once a full methanogenic regime was achieved in the leading reactors, their effluents were fed to fresh packed reactors RE 1.2 and RE 2.2. RE 1.1 reached its full methanogenic regime after 118 days (TMF time to achieve methanogenesis). At this point, its leachate had pH 7.05, alpha factor 0.35, volatile organic acids (VOA) 1405 mg/l HAc, COD 3080 mg/l and 62.02% methane in the biogas. The other leading reactor (UASB 2.1) reached its full methanogenesis regime after 34 days, and its effluent had pH 7.13, alpha 0.36, VOA 1289 mg/l HAc, COD 2280 mg/l, and 60.40% methane in the biogas. After coupling the leading reactors to the corresponding packed reactors, both coupled anaerobic systems showed similar performances regarding the degradation of OFMSW The UASB-RE system showed a faster overall start-up, a slightly higher reduction of organic matter (as volatile solids, VS) of the packed OFMSW and a higher biogas production than RE-RE. Removal efficiencies of VS and cellulose, and the methane pseudo yield were 85.95%, 80.88% and 0.1091 CH4/g-VSfed in RE-RE, and 88.75%, 82.61% and 0.1151 CH4/g-VSfed in RANMAL-RE

Perchloroethylene solubilization with a non-ionic tensoactive [Incremento de la solubilización de percloroetileno con un tensoactivo no uiónico]

Perchloroethylene (PCE) is one of the most commonly reported chlorinated organic contaminants in groundwater, where it forms a dense phase at the bottom of the aquifer and due to its low solubility is very difficult to remove. Thus, it results in an extendedrelease source of contamination to the aquifer. There is the need of enhanced solubility of PCE for further extraction and treatment in pump-and-treat approaches. One way to increase the availability of the pollutant in aquifers for remediation ad situ is by surfactant addition. Tween 80 is a nonionic surfactant with low critical micellar capacity and low toxicity to microorganisms, and represents a good candidate for enhanced PCE solubilization. The aim of this study was to determine the effect of the addition of Tween 80 on the solubility of PCE in a representative water. The maximum concentration of soluble PCE was 1532mg·l-1 at the highest dose of Tween 80 used in this work (800mg·l-1). In contrast the maximum solubility of PCE in water without addition of surfactant was 120mg·l-1. Results show a high PCE solubilization ratio of 12 with Tween 80, compared to ratios of 1.53 and 2.26 for sodium dodecyl sulfate (SDS) and the biosurfactant UH, determined at 800mg·l -1 of each surfactant. High values of other indices, such as K m and the molar solubility ratio, also confirmed the superiority of Tween 80 with respect to SDS and UH, for this application. Tween 80 appears a good candidate for solubilizing high concentrations of PCE in groundwater

Perchloroethylene solubilization with a non-ionic tensoactive [Incremento de la solubilizaci�n de percloroetileno con un tensoactivo no ui�nico]

Perchloroethylene (PCE) is one of the most commonly reported chlorinated organic contaminants in groundwater, where it forms a dense phase at the bottom of the aquifer and due to its low solubility is very difficult to remove. Thus, it results in an extendedrelease source of contamination to the aquifer. There is the need of enhanced solubility of PCE for further extraction and treatment in pump-and-treat approaches. One way to increase the availability of the pollutant in aquifers for remediation ad situ is by surfactant addition. Tween 80 is a nonionic surfactant with low critical micellar capacity and low toxicity to microorganisms, and represents a good candidate for enhanced PCE solubilization. The aim of this study was to determine the effect of the addition of Tween 80 on the solubility of PCE in a representative water. The maximum concentration of soluble PCE was 1532mg�l-1 at the highest dose of Tween 80 used in this work (800mg�l-1). In contrast the maximum solubility of PCE in water without addition of surfactant was 120mg�l-1. Results show a high PCE solubilization ratio of 12 with Tween 80, compared to ratios of 1.53 and 2.26 for sodium dodecyl sulfate (SDS) and the biosurfactant UH, determined at 800mg�l -1 of each surfactant. High values of other indices, such as K m and the molar solubility ratio, also confirmed the superiority of Tween 80 with respect to SDS and UH, for this application. Tween 80 appears a good candidate for solubilizing high concentrations of PCE in groundwater

A Minireview on Slurry Bioreactors for Bioremediation of Soils and Sediments (Paper B-33)

Poggi\u2019s differential coefficient of hysteresis (CHPoggi) has been shown to be a useful tool for describing the adsorptive-desorptive behavior of pollutants on solid matrices. The CHPoggi is defined as the ratio of the derivative of the adsorption isotherm to the derivative of the desorption isotherm, both evaluated in a point of interest J in the space q-C of the equilibrium relationship of the pollutant and solid matrix (Poggi-Varaldo et al., 2002, Interciencia 27 (3): 180-185). The aim of this work was to evaluate the adsorptive-desorptive behavior of lindane in an agricultural soil using CHPoggi. In addition, a useful and simple algebraic equation for CHPoggi was obtained for the particular case when the adsorption isotherm is linear and the desorption isotherm follows the equation of Langmuir. The model solid matrix was an agricultural soil, pH 7.1, with low clay and high organic matter contents. The adsorption of lindane onto this soil was described by a linear isotherm given by the equation qa = 3.91*C, whereas the desorption was better described by a Langmuir-like isotherm given by the equation qd = (32.9*C)/(1 + 1.1*C), with q in mg/kg and C in mg/L. Based on the definition of CHPoggi a simple equation was derived, namely, CHPoggi = qmax *b/kl , where qmax = maximum capacity of adsorption of the Langmuir desorption isotherm (mg/kg); b = coefficient of curve growth-shape in the Langmuir desorption isotherm (L/mg); kl = coefficient of the linear adsorption isotherm (L/Kg). The value of Poggi\ub4s coefficient of hysteresis was calculated at the point of interest J (qj = 28.8 mg/kg, Cj = 6 mg/L) using two different methods: first, a numerical method based on the ratio of the tangents to both isotherms in J (as an approximation to the corresponding derivatives), and second, the algebraic equation already given in the above paragraph. The first method yielded CHPoggi = 6.6, whereas the second one gave CHPoggi = 8.4. The agreement between the two methods indicates that the more simple algebraic equation can be used for calculation of CHPoggi whenever the isotherm equations are known. The value of CHPoggi suggests that the hysteresis lindane-soil is moderate