PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 1, Number 1, 2015
and Fe. However, these metals are valuable micronutrients, therefore, the agronomic application rates were taken into consideration. According to Murray [32], the presence of Fe is more likely linked to the addition of kaolin, the clay used to coat paper which contains 1% Fe 2 O 3 . Furthermore, Fe content in paper mill sludge is negligible compared to the level found in soil, that is lesser than 50,000 μg·g − 1 [33]. Heavy metal levels in pulp and paper mill sludges are generally low enough that the application rates to soil will not be limited by the heavy metals content [34,35]. According to Camberato et al . [21], paper mill sludges generally have lesser metal concentrations than municipal waste biosolids and well within regulatory limits. Similar results were reported by Li et al . [36] and Lu et al . [37] in that the metals of prepared paper mill sludges the major toxic metal was Ba, followed by Cu, Zn, Pb and Cr, which were lower than the thresholds prescribed in GB 5085.3-2007. The use of these types of sludges is not harmful for the soil and plants due to have less concentrations of the heavy metals and could be useful as soil amendments. 3.3. Organic Contaminants of Polycyclic Aromatic Hydrocarbons Seventeen polycyclic aromatic hydrocarbons (PAHs) were analysed in this study (Table 3). The PAHs have received special attention since they have long been recognised as hazardous environmental chemicals. The total concentrations of the 17 PAHs found in the six paper mill sludges were within the range of 218.04 to 3646.67ng·g − 1 . The highest concentration of total PAHs were recorded for sludge from Paper Mill 3 and the lowest was recorded for Paper Mill 2. The total PAHs in raw paper mill sludge was less than 6ng·g − 1 (the value recommended by the draft directive of the European Union for the land disposal of sludges) [31]. Seventeen PAHs were detected at concentrations below the standard of Class 2 followed by the British Columbia Pulp and paper Association, Lands and Parks [25]. In addition, the paper mill sludges showed lower PAHs concentration than some Canadian sewage sludges (traced to 100ng·g − 1 ) that were used in agriculture [38]. 3.4. Dioxins and Furans The presence of trace organic components in pulp and paper solid residues either as contaminants or by-products of the particular process has been an area of concern for regulatory agencies and the general public. A primary concern in the land application of pulp and paper mill residues is due to the presence of trace amounts of chlorinated dioxins and furans. The concentration of dioxins and furans in the Paper Mill 2 sludge was 4.32pg·g − 1 , which is well below the Class 1 standard (10pg·g − 1 ). The low dioxin content makes paper mill sludge a potential organic material for land application in Malaysia. The presence of total dioxin equivalents varied from 1 to 48ng·TEQ·kg − 1 in Ontario (39) and from 2 to 14ng·TEQ·kg − 1 in Quebec. Meanwhile, the Maine Department of Environmental Protection (USA) has stated that sludges containing 27pg·g − 1 or lower are approved for agricultural applications, while levels of 28 – 250pg·g − 1 are restricted to non-agricultural uses [39]. The RPMS has good potential to manage industrial wastes as a resource through waste recovery that will create alternative resources for landfilling [40] and will minimise the negative impact of waste on the environment and human health.
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Article 2 – Environment (sludge)
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