PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 1, Number 1, 2015
In the paper mill sludge, Na content ranged from 0.64% to 0.88%. Meanwhile, the Al content ranged from 1.09% – 1.68% (Table 1). Sodium and Al can occur in pulp and paper mill sludges at levels higher than would typically be found in non-amended soils. However, some studies to monitor these higher contents of Na and Al have been carried out for land application with these residuals [29]. Sodium is used in the pulping process as sodium hydroxide and Al is associated with the use of clays in the paper making process and the use of Al salts (e.g., aluminium sulphate) in the wastewater treatment process [30]. 3.2. Heavy Metals Concentrations of Recycled Paper Mill Sludges The heavy metals concentrations in the paper mill sludge is one of the major issues as it needs to be proven that either heavy metals are above the critical limits or not, which may increase the concentration in the soil. After the analysis it was found that the concentration of heavy metals in the paper mill sludge varied among different paper mills (Table 2). In this study, guidelines for land spreading of pulp and paper mill sludge which were followed by the British Columbia Pulp and paper Association, Lands and Parks [25] were used. From the regulation, only paper mill sludges of Class 1 and Class 2 can be allowed for application on agricultural lands. Total concentrations of heavy metals in the six paper mills, with the exception of Cr, were above the Investigation Level for Malaysian soils [26], which is the level taken at the 95th percentile of the heavy metals data for agricultural soils of Malaysia. Camberato et al . [21] surveyed several organic residues, including pulp and paper mill sludges and biosolids, and reported that the levels of the regulated heavy metals in pulp and paper mill sludges were lower than those found in biosolids, but slightly higher than the “background” levels of these metals in soils. The Cu content of paper mill sludges ranged from 83 to 199mg·kg − 1 with an average of 130.38 mg·kg − 1 which is above the Class 1 limit of 100mg·kg − 1 . Beauchamp et al . [31] reported that concentration of Cu in paper mill sludge varied between 84 and 118mg·kg − 1 . Copper was determined in different chemical additives in the paper making process, and the analyses of the inks (cyan ink) showed a concentration of 10,685 μg·g − 1 of Cu. Therefore, the source of Cu content in the paper mill sludge is likely due to the presence of cyan ink. The lead (Pb) content of paper mill sludges ranged from 43 to 328 mg·kg − 1 with an average of 126.5mg·kg − 1 which is also above the Class 1 limit of 150mg·kg − 1 . In this study, the Cd content of paper mill sludges ranged from 1.3 to 4.09mg·kg − 1 (which is above the Class 1 limit of 3mg·kg − 1 ) with an average Cd content of 2.34%. Concentrations of Cr, Zn and Ni in the paper mill sludge of the six mills were well below the standard concentration of Class 1. The average total concentration of Mn and Fe in six paper mill sludges analysed were 203mg·kg − 1 and 0.34%, respectively. No standard was available for concentrations of Mn
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Article 2 – Environment (sludge)
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