PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 1, Number 1, 2015
CaCO 3 used in the paper finishing process. Most of the agricultural soils in Malaysia are acidic in nature with low soil pH. Hence, in the sludge contains CaCO 3 that could be helpful for the soil improvement. In addition, paper sludge is suitable for land application because CaCO 3 can help neutralise soil acidity due to the cellulosic fibre content that can hold moisture in the soil system. The electrical conductivity values of the six paper mill sludges ranged from 0.51 – 3.08mS·cm − 1 . An EC level of < 2mS·cm − 1 in soil and irrigation water is generally considered a safe level for plants. However, most of the plants can tolerate soils with an EC of 3 – 4mS·cm − 1 .
Figure 2. Physical appearances of different paper mill (PM) sludges from Peninsular Malaysia. The CEC values of paper mill sludges ranged from 3.33 – 28.07cmol (+) kg – 1 . Average CEC content is 14.43cmol (+) kg – 1 (Table 1). Reported CEC values of paper mill sludges from earlier studies varied widely from 5.3 to 297cmol (+) kg – 1 [15 – 19]. Differences in CEC may reflect differences in sludge composition, organic matter fraction and/or clay content [20]. The N content of the paper mill sludges ranged from 0.31% to 4.05%. Average N content was 1.45% (Table 1). In this study, the P content of paper mill sludges ranged from 0.02 to 0.78% with an average P content is 0.18%. Nitrogen and P, which are essential for microbial metabolism, are typically added to wastewater during the secondary treatment process which increases the N and P concentrations of the paper mill sludges [21] with N contents ranging from 0.6% to 8.8% with a median value of 2.3% [22]. Industrial wastewaters from operations like detergent manufacturing and metal coating processes may present P levels higher than 10mg·L − 1 [23]. The carbon content of the paper mill sludges ranged from 18.92% to 33.67% with an average value of 25.61%. The C:N ratios of the paper mill sludges were calculated to be 8.31 – 75.48. The National Council for Air
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Article 2 – Environment (sludge)
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