Aerobic removal of stigmasterol contained in kraft mill effluents

Abstract

Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the *Corresponding author system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL's maximum Chemical Oxygen Demand (COD) removal was 65%, whereas the Biological Oxygen Demand (BOD 5 ) was around 95%.Chamorro, S. et al. 2The removal efficiency of stigmasterol removal was 96% when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.Estrogenic endocrine disruption could be produced by extractive compounds coming from the kraft pulp. High concentrations of extractive compounds (and in particular sterols) are contained in black liquor from the digestion processes, and these are generally recovered by evaporation and combustion . However, there is a small part of black liquor that remains in the fiber and is dragged into the washing processes. Thus, in the discharged kraft mill effluents, concentrations ranging from 0.3 to 3.4 mg/L for sterols and 0.28 to 1.21 mg/L for resin acids can be found (Vidal et al. 2007 where the whitening process consisted in elementary chlorine free processes, finding that a phytosterol reduction process was produced in all cases except in the case of stigmasterol, where it could increase between 192% and 367%. In the activated sludge system, an 88% increase in stigmasterol was observed, and is probably due to the chemical or biological transformation in the precursor treatment system where it was converted into stigmasterol (Cook et al. 1997). However, few studies present results with respect to EDC behavior in aerated lagoons.The goal of this work is to evaluate the performance of aerated lagoon in removing stigmasterol contained in kraft mill effluents. MATERIALS AND METHODS WastewaterThe effluent was obtained from a modern kraft mill that bleaches softwood pulp and is located in Southern Chile. Pinus radiata is the raw material used in the process. The kraft mill effluent was obtained after primary treatment. Table 1 shows the main physicochemical characteristics of this effluent. The effluent was supplemented with 0.022 g/L of NH 4 Cl as nitrogen source and 0.169 g/L of K 2 PO 4 as phosphorus source (BOD 5 :N:P = 100:5:1). InoculumThe aerobic lagoon was inoculated using an aerobic microbial consortium (5 g/L of volatile suspended solid (VSS), 9 g/L of total suspended solid (TSS)) that was obtained from ...

Sensitivity Study Comparing Daphnia obtusa (Kurz 1874) and Daphnia magna (Straus 1820) Exposure to Treated Kraft Mill Effluents, Diethylstilbestrol, and Androstenedione

“…COD and BOD values were 881.0 ± 24.3 and 300.5 ± 9.5, respectively. The COD/BOD ratio (2.9) indicates high concentrations of recalcitrant compounds, such as phenolic compounds, tannin, and lignin, among others (Vidal et al 2007;Xavier et al 2009). On the other hand, Table 1 shows the presence of β-sitosterol and stigmasterol with concentrations of 0.333 ± 0.028 and 0.069 ± 0.014 respectively.…”

Steroidal Metabolites in Chilean River Sediments Influenced by Pulp Mill Effluents

“…13 However, concentrations lower than those informed here have been showed to generate a biological impact. 2 Despite being selected the site BB1 (near Negrete city) to be downstream effluent diffuser, sitosterol was not detected, probably due to the scarcity of fine sediment in a river section of greater water current and consistent with the fewest organic matter analyzed. )…”

“…10,11,12 Chamorro et al 13 informed about the high estrogenicity related to effluents of the same industrial activity on the Biobío basin, even with tertiary treatment in the plant. If it is considered that these and other metabolites derived from a biological or chemical transformation in the same sediments can remain active even in very low concentrations, 12,14 constituting a challenge to the analytics modern analysis techniques such as those derived from the advancement in mass spectrometry, which are able to reach increasing sensitivity in metabolite detection at trace concentrations.…”

Sex‐Related Embryotoxicity of Pulp Mill Effluent Extracts in Medaka (Oryzias latipes) Female Leucophore‐free FLFII Strain

“…Differences in removal effectiveness of compounds such as phytosterols with both treatment technologies have been previously demonstrated (Xavier et al 2009), with the activated sludge treatment being more effective. However, these results should be considered with caution, due to the varying efficacy of both treatment technologies, which depend on critical operational aspects such as flow rate, retention time, and raw materials that often reduce their efficiencies (Chamorro et al 2009). Overall, our data indicate that 0.005 EEq of the initial effluent present in the treatments prepared from SP1 and SP2 pulp mill effluent samples (equivalent to~0.75-8.4 ng/mL of beta-sitosterol, respectively) were capable of causing embryotoxicity, suggesting poor survival of early life stages of natural fish populations that inhabit environments receiving pulp and paper mill industrial discharges, irrespective of their effluent treatment.…”