Effect of Composting on Polycyclic Aromatic Hydrocarbons Removal in Sewage Sludge

Abstract

Changes in the concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) identified by the US Environmental Protection Agency as priority pollutants were investigated during the composting process of sewage sludge mixed with rapeseed marc (9:1, weight base). Results showed that total PAHs concentrations of the sludge sampled in different seasons had far exceeded the accepted Europe Union cut-off limits for land application. Phenanthrene, fluorene and dibenz(a, h) anthracene were dominant PAHs in the sludge, accounting for 62.8~69.6% of the total amount of the 16 PAHs. Composting appeared to be an effective method for the removal of PAHs in sewage sludge. After 50 days of composting, a significant reduction of concentration of the total PAHs was detected as compared with the initial concentration in composting material. The significant relationship between the biodegradation of organic matter and the losses of Σ16 PAHs during composting indicated that microbial degradation was the key process responsible for the efficient removal of PAHs from the sludge. Among all tested PAHs, fluorene was the most recalcitrant and became the primary residual PAH in the composted material. The lower removal rate of fluorene during composting was a limiting factor for the potential land application of the sludge. Further studies are needed to enhance the removal of fluorene in order to achieve a safe utilization of this sludge.

Achilles heel of environmental risk from recycling of sludge to soil as amendment: A summary in recent ten years (2007–2016)

“…Hua et al (2008) detected that total PAH concentrations in sludge in different seasons far exceeded the proposed European Union limits for sludge applied to soil. Feng et al (2014) found that the PAH content of sludge-amended soil increased as the sludge dose increased and that some PAHs were taken up from the soil by plant roots.…”

Sequential Remediation Processes for Effective Removal of Oil from Contaminated Soils

“…Hua et al (2008) observed a maximum temperature of 65°C on day 7 while composting polycyclic aromatic hydrocarbons in sewage sludge which then declined to 35°C after 15 day and reached ambient temperature after 30 days. Ghaly et al (2007) reported maximum steady temperatures of 32 and 40°C after 60 h for continuous and intermittent mixing during the bioremediation of toluene contaminated soil.…”

“…According to Walker et al (1999), an intense decrease of moisture content will reduce the metabolic rate and affects the effectiveness of the bioremediation process while high moisture content can reduce the oxygen transfer. Hua et al (2008) reported a steadily decreasing trend of moisture content from an initial value of 62.5% to a final value of 30.2% after 60 days during the composting of sewage sludge mixed with rapeseed marc. Guardia et al (2010) observed a decrease in the moisture content of composted food waste with wood chips the mixture from 63.4-50.5% after 37 days of composting.…”

Response of soil enzyme activities to synergistic effects of biosolids and plants in iron ore mine soils

“…In fact, the handling of biosolids and the achievement of environmentally sound and economically feasible disposal strategies are currently major issues in wastewater treatment, not only in Swaziland but in many places around the world (Deepesh et al 2014;Fytili and Zabanitou 2008;Contin et al 2012). The controlled application of biosolids in mine sites can greatly improve soil physicochemical conditions since these organic residues contain organic matter (OM) that acts as a soil conditioner which can improve soil aeration, waterholding capacity (Bourioug et al 2014;Hua et al 2008;Wong et al 1998, etc. ), contributing to erosion control, slope stabilization (Luczkiewicz 2006) and aggregate stability (Bozkurt et al 2010).…”

“…However, since land application of biosolids is still generally regarded as controversial due to possible human health and environmental risks (Luczkiewicz 2006), on account of elevated metal concentrations contained therein (Bourioug et al 2014;Hua et al 2008;Forsberg and Ledin 2006;etc. ), the SWSC commissioned a number of studies to investigate the impacts of biosolids in mine soils with regard to various aspects including soil physicochemical conditions, plant establishment and growth and metal accumulation in plants.…”