This paper presents the content changes in the Chemical Oxygen Demand (COD) solubilised in hydrolisates obtained from thermally disintegrated municipal waste biofractions. A series of tests related to biowaste undergoing thermal treatment at the following temperatures: 55, 75, 95, 115, 135, 155 and 175°C were conducted for 0.5, 1 and 2 hours. The highest increase in COD solid fraction solubilisation (238%) was observed for the samples disintegrated at 175°C for 2 hours. The values of the reaction rate coefficient k20 = 0.6 d-1 and temperature coefficient θ = 1.023 were determined. Statistical analysis of the multiple regression (correlation coefficient R = 0.89) showed that the temperature has a greater impact on COD solid fraction solubilisation - determined β = 0.66. The multiple correlation coefficient for the treatment time was β = 0.61.
The paper presents preliminary results of investigations on a relationship between turbidity and other quality parameters in the SBR plant effluent. The laboratory tests demonstrated a high correlation between an effluent turbidity and a total suspended solids (TSS) concentration as well as between TSS and COD. Such a relationship would help to continuously monitor and control quality of a wastewater discharge using turbidity measurement.
The double barrier separate confinement heterostructure (DBSCH) design aimed at reduction of vertical beam divergence and increase of catastrophic optical damage (COD) level for high power laser diodes (LDs) operation is presented. Insertion of thin, wide-gap barrier layers at the interfaces between waveguide and cladding layers of SCH gives an additional degree of freedom in design making possible more precise shaping of the optical field distribution in the laser cavity. By comparison with the large optical cavity (LOC) heterostructure design it has been shown that the low beam divergence emission of DBSCH LDs can be attributed to the soft-profiled field distribution inside the cavity. This ‘soft mode profile’ seems to determine narrow laser beam emission rather than the field distribution width itself.
The potential problem with the soft-profiled but relatively narrow (at half-maximum) mode distribution is a lower COD level. Widening of the mode profile by the heterostructure design corrections can increase it, but care must be taken to avoid excessive decrease of confinement factor (Γ). As a result it is shown that DBSCH design is possible, where the low beam divergence and high COD level is achieved simultaneously.
Wide stripe gain-guided LDs based on GaAsP/AlGaAs DBSCH SQW structures have been manufactured according to the design above. Gaussian-shaped narrow directional characteristics are in relatively good agreement with modelling predictions. Vertical beam divergences are 13–15◦ and 17–18◦ FWHM for design versions experimentally investigated. Threshold current densities of the order of 350–270 Acm-2 and slope efficiencies of 0.95 and 1.15 W/A have been recorded for these two versions, respectively. Optical power at the level of 1 W has been achieved. The version with lower beam divergence proves to be more durable. Higher optical power levels are to be obtained after heterostructure doping optimisation.