No abstract

Activated sludge systems operated under alkaline conditions remove EDTA. To improve EDTA removal a better understanding of EDTA biodegradation and its intermediates as well as knowledge of kinetic parameters are a prerequisite. Activated sludge appeared to degrade EDTA via ethylenediaminetriacetate (ED3A). The sludge was able to split ED3A into readily biodegradable iminodiacetic acid and iminoacetaldehydeacetate. The maximum growth rate of EDTA-grown sludge was approximately 0.15 days−1. The Km for EDTA and maximum oxidation rate of EDTA-grown sludge were 10 mg/L and 135 mg O2 g−1 SS day−1. Specially cultivated activated sludge degraded EDTA under neutral conditions and was capable of degrading the FeEDTA complex at a low rate. Bioaugmentation of EDTA-grown sludge enabled EDTA removal in a treatment system under neutral conditions.

A bacterium capable of utilizing the alkyl chains of didecyldimethylammonium salt was isolated from activated sludge. In addition, the isolate also utilized didodecyldimethylammonium salt, ditetradecyldimethylammonium salt and alkyltrimethylammonium salts (C10 to C18) as sole source of carbon and energy. The broad substrate with respect to the alkyl chain length was also demonstrated with oxidation rates of various quaternary ammonium salts by didecyldimethylammonium chloride-grown cells. The oxidation rate decreased with increasing alkyl chain lengths. The main factor impeding the biodegradation of dialkyldimethylammonium salts with long alkyl chains is probably the low bioavailability of water-insoluble chemicals. The biodegradability of dialkyldimethylammonium salts was therefore determined in flow-through columns at concentrations below their aqueous solubility. Dialkyldimethylammonium salts adsorbed on silica gel particles packed in flow-through columns were immediately metabolized by the isolate when dissolved. Microorganisms present in river water pumped through a sterile column degraded dissolved dicocodimethylammonium salts within a week.

A bacterium capable of utilising p-toluenesulphonamide was isolated from activated sludge. The isolated strain designated PTSA was identified as a Pseudomonas sp. using chemotaxonomic and genetic studies. Pseudomonas PTSA grew on p-toluenesulphonamide in a chemostat with approximately 90% release of sulphate and 80% release of ammonium. The isolate was also able to grow on 4-carboxybenzenesulphonamide and 3,4-dihydroxybenzoate but did not grow on p-toluenesulphonate. The transient appearance of 4-hydroxymethylbenzenesulphonamide and 4-carboxybenzenesulphonamide during p-toluenesulphonamide degradation proves oxidation of the methyl group is the initial attack in the biodegradation pathway. Both metabolites of p-toluenesulphonamide degradation were identified by high-performance liquid chromatography-mass spectrometry. 4-Carboxybenzenesulphonamide is probably converted into 3,4-dihydroxybenzoate and amidosulphurous acid. The latter is a chemically unstable compound in aqueous solutions and immediately converted into sulphite and ammonium. Both sulphite and ammonium were formed during degradation of 4-carboxybenzenesulphonamide. ß

Recently developed photobleachable polymers show a loss of < 0. 1 dB/cm at 1300 nm and < 0. 15 dB/cm at 1550 nm. Nonchromophore containing polymers show filmwaveguide losses of < 0. 1 dB/cm at 1300 nm and 1550 nm. Refractive indices in these materials can be tuned within a range of 0.05 by changing the polymer composition. Multilayers of cross-linked (solvent resistant) layers, each 2-10 microns have been deposited by multiple spinning steps. Using these multilayers, fully embedded, fiber-compatible stripwaveguide structures have been created by masked bleaching of multilayers with chromophore containing corelayers. The lateral refractive index contrast is thereby tuned by changing the chromophore content of the corepolymer. Poling-induced loss has been investigated by wavelength-and polarization dependent measurements of losses in films. The results indicate that this loss is due to increased scattering. Bleached channel waveguides in a poled (at 125 V/sm) nonlinear optical (nb) polymer have been made showing losses of < 1 dB/cm at 1300 rim. Rapid photodegradation at 1300 rim has been observed in stilbene containing channel waveguides. In a nitrogen atmosphere no degradation was seen. The same is true for waveguides in air at 1550 rim. This suggests the attack of the stilbene chromophores by singlet oxygen. Therefore a new generation of low-loss, linear-and nonlinear optical polymers based on singlet oxygen resistant molecules has been developed.The linear optical polymers are used for the realization of low-insertion loss (< 2 dB), digital (switch voltage 3-6 V) and efficient (switching power <100 mW, cross talk -20 dB) pigtailed and packaged 1x2 switches. They utilize the strong thermooptic effect in polymers. Their switching time is therefore limited to 1 ms whereas their polarization dependence is <0.3 dB.