Optimization of the electrodialytic phosphorus recovery from sewage sludge ash

Phosphorus (P) is becoming a scarce element due to the decreasing availability of primary sources. Therefore, recover P from secondary sources, e.g. waste streams, have become extremely important. Sewage sludge ash (SSA) is a reliable secondary source of P. The use of SSAs as a direct fertilizer has very restricted legislation due to the presence of inorganic contaminants. Furthermore, the P present in SSAs is not in a plant-available form. The electrodialytic (ED) process is one of the methods under development to recover P and simultaneously remove heavy metals. The present work aimed to optimize the P recovery through a 2 compartment electrodialytic cell. The research was divided in three independent phases. In the first phase, ED experiments were carried out for two SSAs from different seasons, varying the duration of the ED process (2, 4, 6 and 9 days). During the ED treatment the SSA was suspended in distilled water in the anolyte, which was separated from the catholyte by a cation exchange membrane. From both ashes 90% of P was successfully extracted after 6 days of treatment. Regarding the heavy metals removal, one of the SSAs had a better removal than the other. Therefore, it was possible to conclude that SSAs from different seasons can be submitted to ED process under the same parameters. In the second phase, the two SSAs were exposed to humidity and air prior to ED, in order to carbonate them. Although this procedure was not successful, ED experiments were carried out varying the duration of the treatment (2 and 6 days) and the period of air exposure that SSAs were submitted to (7, 14 and 30 days). After 6 days of treatment and 30 days of air exposure, 90% of phosphorus was successfully extracted from both ashes. No differences were identified between carbonated and non-carbonated SSAs. Thus, SSAs that were exposed to the air and humidity, e.g. SSAs stored for 30 days in an open deposit, can be treated under the same parameters as the SSAs directly collected from the incineration process. In the third phase, ED experiments were carried out during 6 days varying the stirring time (0, 1, 2 and 4 h/day) in order to investigate if energy can be saved on the stirring process. After 6 days of treatment and 4 h/day stirring, 80% and 90% of P was successfully extracted from SSA-A and SSA-B, respectively. This value is very similar to the one obtained for 6 days of treatment stirring 24 h/day.

Valorization of grape pomace through hot compressed water extraction/hydrolysis

The world energy consumption is expected to increase strongly in coming years, because of the emerging economies. Biomass is the only renewable carbon resource that is abundant enough to be used as a source of energy Grape pomace is one of the most abundant agro-industrial residues in the world, being a good biomass resource. The aim of this work is the valorization of grape pomace from white grapes (WWGP) and from red grapes (RWGP), through the extraction of phenolic compounds with antioxidant activity, as well as through the extraction/hydrolysis of carbohydrates, using subcritical water, or hot compressed water (HCW). The main focus of this work is the optimization of the process for WWGP, while for RWGP only one set of parameters were tested. The temperatures used were 170, 190 and 210 °C for WWGP, and 180 °C for RWGP. The water flow rates were 5 and 10 mL/min, and the pressure was always kept at 100 bar. Before performing HCW assays, both residues were characterized, revealing that WWGP is very rich in free sugars (around 40%) essentially glucose and fructose, while RWGP has higher contents of structural sugars, lignin, lipids and protein. For WWGP the best results were achieved at 210 °C and 10 mL/min: higher yield in water soluble compounds (69 wt.%), phenolics extraction (26.2 mg/g) and carbohydrates recovery (49.3 wt.% relative to the existing 57.8%). For RWGP the conditions were not optimized (180 °C and 5 mL/min), and the values of the yield in water soluble compounds (25 wt.%), phenolics extraction (19.5 mg/g) and carbohydrates recovery (11.4 wt.% relative to the existing 33.5%) were much lower. The antioxidant activity of the HCW extracts from each assay was determined, the best result being obtained for WWGP, namely for extracts obtained at 210 °C (EC50=20.8 μg/mL; EC50 = half maximum effective concentration; EC50 = 22.1 μg/mL for RWGP, at 180 ºC).

Consumer satisfaction with water, wastewater and waste services in Portugal

While the concept of consumer satisfaction is a central topic in modern marketing theory and practice, citizens' satisfaction with public services, and especially water and waste services, is a eld that still remains empirically rather unexplored. The following study aims to contribute to this area by analysing the determinants of user satisfaction in the water, wastewater and waste sector in Portugal, using a unique survey of 1070 consumers undertaken by the Portuguese Water and Waste Regulator ERSAR. I perform an analysis of the relation between overall service satisfaction and attributespeci c service satisfaction with an ordered logit model. I then explore if subjective consumer satisfaction can be re ected by ERSAR's technical performance indicators. The results suggest that overall consumer satisfaction is driven by consumer's satisfaction with speci c service aspects but unrelated to socioeconomic and demographic characteristics. Furthermore, I show that there is no monotonic association between ERSAR's technical performance indicators and consumers' levels of satisfaction.

Chlorite Dismutase from perchlorate reducing bacteria. A potential biocatalyst to eliminate chlorinated species from polluted water resources and industrial wastes

Magnetospirillum (M.) sp. strain Lusitani, a perchlorate reducing bacteria (PRB), was previously isolated from a wastewater treatment plant and phylogenetic analysis was performed to classify the isolate. The DNA sequence of the genes responsible for perchlorate reduction and chlorite dismutation was determined and a model was designed based on the physiological roles of the proteins involved in the pcr-cld regulon. Chlorite dismutase (Cld) was purified from Magnetospirillum sp. strain Lusitani cells grown in anaerobiosis in the presence of perchlorate. The protein was purified up to electrophoretic grade using HPLC techniques as a 140 kDa homopentamer comprising five ~28 kDa monomers. Steady-state kinetic studies showed that the enzyme follows a Michaelis-Menten model with optimal pH and temperature of 6.0 and 5°C, respectively. The average values for the kinetic constants KM and Vmax were respectively 0.56 mM and 10.2 U, which correspond to a specific activity of 35470 U/mg and a turnover number of 16552 s-1. Cld from M. sp. strain Lusitani is inhibited by the product chloride, but not by dioxygen. Inhibition constants KiC= 460 mM and KiU= 480 mM indicated that sodium chloride is a weak mixed inhibitor of Cld, with a slightly stronger competitive character. The X-ray crystallography structure of M. sp. strain Lusitani Cld was solved at 3.0 Å resolution. In agreement with cofactor content biochemical analysis, the X-ray data showed that each Cld monomer harbors one heme b coordinated by a histidine residue (His188), hydrogen-bonded to a conserved glutamic acid residue (Glu238). The conserved neighboring arginine residue (Arg201) important for substrate positioning, was found in two different conformations in different monomers depending on the presence of the exogenous ligand thiocyanate. UV-Visible and CW-EPR spectroscopies were used to study the effect of redox agents, pH and exogenous ligands on the heme environment.