Treated slurry

Foaming was controlled by situating an impeller, which was driven at 1400 rev/min, under a square-section pyramidal draft tube. The impeller sucked headspace air and foam into the treated slurry. As foam built up it flowed down the tube and was recycled by the impeller. No other mechanical device was needed to control foam. 

The destmction of carbonaceous substrates during treatment resulted in significant (P=0.001) decreases of TS, VS, BODw, VFA (Table III) and COD (Fig 2) in every run. The destmction of VS and TS were very similar in each run being in the range 2-20%. COD destmction was higher, 21-38%, while BODw removal was 46-85%. Destmction of VFA was nearly total at 98-100%. Ethanoic acid was usually the only individual VFA found in the treated slurries. This was taken to be the residual ethanoic acid (6),... 

Fig. 3 Measured BOD, in treated slurry and values predicted from expression.

Table HI Mean composition of the treated slurries. The percentage of parentheses.

The BOD expression of Evans et al (ii) did not need to include a term for endogenous decay. Thus, BODw in treated slurry becomes a function of residence time and feed BODw only. Evans s expression was ... 

Odour control and stability of treated slurries The treatments would all successfully control odours, since the total VFA concentrations... 

The allowance for nitrified oxygen still did not fully account for great stability of the treated slurry from mn 4H, which probably partly resulted also from the low NH3-N content. More experimental data is needed to derive a satisfactory term for the inhibitory effect of NH3-N on me thanogenesis. 

The stability of the treated slurries during subsequent anaerobic storage increased from 10 to 56 days as both the treatment residence time and the aeration rate increased. 

The stability of the treated slurries was linearly related to the oxygen consumed during treatment, which could be calculated using an expression for nitrification derived in the present study and one for COD changes produced by Evans et al (4) from laboratory scale experiments. 

An expression predicting treated slurry BODw during treatment with redox control is presented. 

Odour will return in treated slurry as a result of post treatment fermentation. The concentration of readily fermentable substrates, measured as BOD5, provide an indicator of this problem. In continuous culture without oxygen limitation the BOD5 can be described by a model derived from the Monod (13) model of microbial growth (14). The supernatant BOD5 (g/1) from treatment at 15 to 45°C, was described by equation 3 and the whole BOD5 by equations 4 and 5(15). 

The optimum design parameters for aerobic treatment must be those which select for the most desirable mixture of microbes and metabolic activity that brings about a degree of degradation so that the treated slurry characteristics meet the treatment objectives. 

Samples of treated slurry were obtained from laboratory-scale continuous culture reactors (3 15 litres) during a series of treatments studying the effects on residual slurry quality of mean treatment time, reaction temperature, dissolved oxygen level and pH value (27). Some were also collected from a 2.4m3 pilot plant which was operating at 35°C and 7 day residence time and with dissolved oxygen saturation of 0 to 40%. The pilot plant was treating separated stored piggery slurry (TS 21 g/1 COD 26 g/1 ). 

Samples of raw and treated slurry were centrifuged at 10,000g for 20 minutes at 10°C, as described by Hissett et al (25), to prepare the supernatants for the measurement of BOD. 

Specific odorants such as VFA, TIP or individual compounds can be used to indicate odour offensiveness but their absence does not give any information about the possiblity of other odorants being present. The offensive odours of treated slurry, which did not contain the 6 VFA, 3 phenols, 2 indoles or ammonia, were due to compounds not determined in these experiments. There are a large number of other odorants cited with very low threshold levels (28 29) which could be responsible for this odour offensiveness. Since the odour offensiveness test is so subjective any indicator must have... 

Beside the 61 kW total performance, the specific performance projected to the amount of treated slurry amounts to 0.41 kW per m3. The specific electric energy consumption per cubic meter 2.14 kWh. 

The IT process can treat slurries containing up to 40% solids and contaminants in the 1000s parts per million range. 

Mixflo can only be used to treat aerobically biodegradable contaminants it cannot treat metals. In addition, the technology only treats slurries that can be pumped and can pass through a 0.5-inch mesh. 

The use of a US probe [11,12] orthe sequential use of a US bath and a probe to assist slurry formation [11] is much less frequent. Treated slurries can be transferred to an autosampler or atomizer in various ways ranging from manual pipetting of aliquots to automated dynamic procedures. Once an aliquot has been transferred to an autosampler cup, it can be homogenized by manual shaking, vortexing, with a microprobe, an inert gas stream, etc. 

It is usually difficult to observe visually a change in floe structure in a concentrated slurry. The two best indications that an effective quantity of chemical has been added is a sudden thickening or increase in viscosity of the slurry and the formation of riveriets on the surface of a spatula when treated slurry is shaken from it. It is generally necessary to exceed a threshold quantity of chemical before there is a measurable improvement. The proper dosage becomes an economic balance between the cost of additional chemicals and the savings resulting from a reduction in filter area. 

C thiols detected in the "control slurry" (no tributylphosphine added) are interpreted as being in the unbound (or free) state thiols detected in "slurry with tributylphosphine" are interpreted as free plus bound species the thiol bound" was calculated from [(thiols in tributylphosphine treated slurry) - (thiols in control)] X 100%/(thiols in tributylphosphine treated slurry). 

When the experiment was completed, the container was removed from the RF chamber and cooled at room temperature. The treated slurry was filtered through a Whatman no. 4 filter paper in a Buchner funnel. The filtered cakes were washed by deionized water to neutralize the pH to 7.0 and stored for enzymatic hydrolysis. The liquid fraction after pretreatment contained oligosaccharides, which could not be easily quantified thus, an extra step was performed to convert those oligosaccharides into monosaccharides before monosaccharide measurement. National Renewable Enei f Laboratory (NREL) procedure (LAP 002) was used for this conversion [16]. 

Synthesis of M41S mesoporous materials was attempted using MFI type zeolite as sources of silica and aluminum, that is, dissolution of MFI zeolite in an alkaline solution and successive precipitation of dissolved aluminosilicate species with a surfactant, cethyltrimethylammonium bromide (CTAB). Pure phase of M41S was obtained when the filtrate of alkali-treated slurry was mixed with CTAB and crystallized at 293K. The M41S materials obtained in this method showed a catalytic activity originated from Bronsted acid site of the parent MFI zeolite. This method enables us to obtain a new type of mesoporous materials, which have both characteristics of zeolitic and mesoporous materials a strong Bronsted acidity and mesopores with a uniform size. 

The processes that can be used to separate heavy metals from industrial liquid waste streams are given in Table 3.4, processes that can treat various tars or solids are shown in Table 3.5, and processes suitable for treating slurries and sludges are listed in Table 3.6. 

TABLE 3.6 Processes That Can Treat Slurries or Sludges... 

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