Thermal stability and thermodynamic properties of hybrid proton-conducting polyaryl etherketones.

The thermal and structural stability of sulfonated cross-linked PEEK (polyether ether ketone) and its silicon-containing class II hybrid derivatives were characterized by combination of mass spectrometry, infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Thermodynamic properties of the hybrids were determined, including glass-transition temperature, degree of crystallinity, and thermal stability. The decomposition processes of the hybrid polymers could be consistently interpreted and their energetics quantitatively determined. The introduction of inorganic silanol moieties improves the thermal stability compared to sulfonated products.

Rethinking sewage treatment by enhancing primary settling with low-dosage lime.

This work presents a thorough fractionation of COD in raw sewage, followed by pilot plant coagulation tests with low-dosage lime (pH 9). Through a physical separation (sieving and crossflow filtration) total COD in the raw sewage was partitioned among eight size fractions in the range of 150-0.02 microm. In addition, respirometric tests were performed to measure the biodegradability of the different size fractions. More than 60% of COD was associated with settleable and supracolloidal particles (size > 1 microm), which are characterised by slow biodegradability. Coagulation with lime increased COD removal efficiencies in the primary treatment from typical 30-35%, up to 65-70%, suggesting that lime may induce the almost complete removal of the slowly settling, slowly biodegradable supracolloidal particles in the primary treatment. On the basis of these results a non-conventional sewage treatment scheme is proposed, considering that there is plenty of space for improving primary treatment efficiency through sewage coagulation. Higher primary treatment efficiency may present several advantages, including lower aeration energy in the subsequent biological unit and higher energy recovery from sludge digestion.

Size fractionation of COD in urban wastewater from a combined sewer system.

The objective of this work was to determine the partitioning of the pollutant load in urban wastewater in order to improve the conventional sewage treatment. In addition to settling tests, physical fractionation of COD in the degritted influent of Roma-Nord sewage treatment plant was performed via sequential filtration through sieves and membrane filters of the following pore size: 150-100-50-25-1-0.2 microm, and 100 kD (about 0.02 microm). Biodegradability studies were also performed on the different size fractions. Size fractionation showed that COD in Roma-Nord sewage is predominantly associated with settleable and supracolloidal (> 1 microm) particles, each size range including about 40% of total COD. Biodegradability tests indicated that the large fraction of COD associated with supracolloidal particles, which are not removed in the primary treatment, is characterised by slow degradability. This suggests that removal of these particles prior to biological treatment may greatly improve the overall treatment scheme. Preliminary pilot plant coagulation tests with lime at pH 9 showed that lime-enhanced primary treatment may increase COD removal efficiencies from typical 30-35% up to 65-70%, by inducing almost complete removal of the COD fraction associated with supracolloidal particles.

Behaviour of Cd, Cr, Mn, Ni, Pb, and Zn in sewage sludge incineration by fluidised bed furnace.

Cd, Cr, Mn, Ni, Pb, and Zn behaviour during sewage sludge incineration was investigated in seven pilot tests using a circulating fluidised bed furnace. Dewatered sludge at a solids concentration of 15-18% was fed to the furnace either alone (two tests) or spiked with chlorinated organic compounds (five tests). The behaviour of metals in the fluidised bed furnace was studied by comparing metal concentrations in the two main ash streams: ash separated from the cyclone immediately following the fluidised bed furnace, and fly ash recovered in the final bag filter. A metal enrichment factor was defined as the ratio of metal concentration between filter ash and cyclone ash. Only Cd and Pb showed any significant enrichment. Their enrichment factors were mainly affected by chlorine concentration in the feed sludge. To check whether simple equilibrium models may explain and predict metal behaviour, experimental data were compared with percentage of the metal vaporisation in the combustion chamber predicted using a thermodynamic model. Discrepancies between model predictions and experimental results are accounted for by considering that kinetics may be a limiting factor in the formation of metal chloride gaseous species. Due to the very short sludge residence time in the fluidised bed furnace, the gaseous compounds have little chance to evolve completely.