Waste solids with time

The composition of leachate is important in determining its potential effects on the quality of nearby surface water and groundwater. Contaminants carried in leachate are dependent on solid waste composition and on the simultaneously occurring physical, chemical, and biological activities within the landfill. The quantity of contaminants in leachate from a completed landfill where no more waste is being disposed of can be expected to decrease with time, but it will take several years to stabilize. 

There is an apparent upper limit to the strength of waste a biological system ean handle in a liquid system. In some cases the constraint is oxygen transfer. In other eases it is the solids concentration in the mixed liquor and the shear whieh is neeessary to keep it in suspension. Recent work with membranes replaeing the elarifiers have indicated that the upper limit to solids is between 2% and 4% total solids, but not all of that is active biomass. The solids retention time in the system is often well over 40 days. The apparent upper limit on waste expressed as BOD is about 600mg/l -800 mg/1. Stronger wastes ean be treated, but they comprise a portion of the total flow and in effect are diluted. 

The thermodynamic incompatibility of many of the solid phases present with each other as well as their local environment, results in formation of secondary minerals. Although the secondary materials may comprise only a small volume fraction of the waste, they (1) tend to increase in amount with time, as weathering processes proceed, (2) typically form at grain surfaces and are thus physically liable to react with percolating gas or liquids, and (3) may exhibit sites suitable for sorption or crystallo-chemical incorporation of trace elements (see Donahoe, 2004). Frequently observed secondary minerals include jarosite and ettringite the former is known to sorb ions such as Mn and As, whereas ettringite can form solid solutions, in which SO4 is replaced by Cr04 (Kumarathasan et al. 1990). 

Wear breathing apparatus, eye protection, laboratory coat, and butyl rubber gloves. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Moisten and shovel mixture into pail for dispersion in an excess of dilute hydrochloric acid (1 volume of concentrated acid diluted with 2 volumes of water). Allow to stand, with occasional stirring, for 24 hours, and then run solution to waste, diluting with at least 50 times its volume of water. The solid residue can then be treated as normal refuse. The spill site should be washed with water and soap or detergent.2,4... 

Fixed-biofilm processes offer the advantage of high concentrations of biomass in relatively small reactors, as little biomass is lost in the effluent. The result is a long solids retention time (necessary to foster slow-growing microorganisms) and the possibility of degrading hazardous contaminants or wastes with low concentrations of organics. 

Biological solids retention time (Oc) has been suggested in this paper as the kinetic based parameter of choice for use in design and control of fiuidized culture continuous fiow biological processes. The value of Oc selected for design of the process, (Oc ), directly determines the volume of reactor needed for a conventional digester system and a given waste fiow (Q) since the value of Oc is equal to the hydraulic retention time (0). The relationship between Oc and the reactor volume for the system with recycle is more complex and involves consideration of the effects of solids recycle rate and recycle solids concentration. 

The use of solid acid catalysts would eliminate waste disposal problems and allow for more advantageous control of product selectivities. However, rapid deactivation of these solid acid catalysts is a problem that significantly hinders the effective performance and selectivity of these catalysts. We have studied the performance of various solid acid catalysts for their activity/deactivation characteristics and also their shape selective effects. Specifically in the liquid phase system, unlike previous researchers, we have studied the activity/deactivation evolution with time on stream rather than rely on final product distribution only. This approach has allowed us to obtain unique data that clearly describe the deactivation pattern of these catalysts. 

A hazardous waste incinerator is burning a waste mixture containing solids with 50% excess air at 2100°F with a residence time of 2.5 s. The stack gas flowrate was determined to be 14,280 dscfin. The composition of contaminants in the stack gas is given below ... 

Problems associated with recirculation of waste solids are caused by the fact that, in most cases, materials are physically and/or chemically unsuitable for direct use, and, therefore, must be converted to a different shape, size, and/or composition. The most common characteristic that needs to be changed is particle size. Often, at the same time, density and flowability must be increased and, in some cases, the specific surface must be altered. 

Because dissolved sulfite is present in a typical CaO/CaCOj scrubber system, it is conceivable that unsaturated acids would sulfonate if added directly to the scrubber system. For the sulfonation reactions, a scrubber system can be characterized as a completely stirred tank reactor with a residence time equal to the ratio of solution inventory and the rate of loss of solution with the waste solids. Assuming 10 mM total dissolved sulfite, 55°C, 0.5 N ionic strength, and 130 hours residence time, the fraction of unsulfonated acid that would leave the system is 6%... 

Another characteristic of the waste solids was the deterioration of their settling properties with time. This effect was observed on various occasions, most notably during a filter repair downtime. Solids with excellent settling properties had been... 

Unlike pilot tests where the waste cake contained 55 to 65% solids, similar mechanical and related problems resulted in a very moist waste cake at Scholz. The capability of the system to generate solids with excellent settling properties for sustained periods of operation was initially demonstrated in pilot plant tests and clearly reconfirmed at Scholz. However, poor solids were also generated on various occasions. The mechanism for their formation needs to be better understood so that their generation can be prevented at all times. The practical limits for the tolerance of the system to oxidation are yet to be determined it appears, though, that the system can tolerate oxidations equivalent to 15 to 20% of the SO2 removed. The power consumption by the full-scale system should be in the range of 1 to 1.5% of the full boiler output. 

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