The Effects Of CKD On Sludge Stabilization

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The effect of CKD on sludge stabilization compared with chemical stabilization with Lime is introduced in Table (3). Also comparison between different concentrations of sludge is introduced. Different dosages of CKD were examined and the dosage that achieves stabilization was 50% and 60% for thickened and diluted sludge respectively, while the required dosage of Lime was ranged between 22 and 29%. The required lime dosage complies with the results of EPA [4], Wang [18], Rahman [11] and Salah [12]. From table (2) it is clear that calcium oxide represents only 50% of the CKD composition, this explain why the required CKD dose was higher than twice that of Lime
Table (3) pH for treated sludge with CKD and Lime
Sludge type TS% CDK dosage (%TS) pH*
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At any operating time the sludge interface height for treated sludge is lower than that for untreated sludge. The Zone settling velocity is determined as the slope of the linear part, which in the calculations is defined as the steepest slope in the curve [16], Based on this criteria the zone settling velocity increased from 43.2(m/d) for untreated sludge to 98.4(m/d) for treated sludge, for factor of safety equal to 2 the hydraulic loading rate of gravity thickeners will be 21.06 (m/d), and 49.20 (m/d) for the untreated and treated sludge …show more content…
Results of treated sludge complies with the results published by EPA [4] as they found that only two days are enough for treated sewage sludge with lime and some other conditioners to get sludge solid content varied between 20 and 30%.
Figure (6) shows the relation between drying time and sludge pH value, the results treated sludge shows that the pH value remains above 10.50 for the whole test which lasts for 5 days. This result complies with the results of Salah [12] who studied using CKD as stabilizer for thickened and dewatered sludge and found that using CKD with dosage more than 30% increased the pH value to be 11 for 7 days.
3.5 Additional Sludge

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