Fate of nonylphenol polyethoxylates and nonylphenoxy acetic acids in an anaerobic digestion process for sewage sludge treatment

Abstract

Many environmental problems caused by endocrine disruptors (EDs) have been reported. It is reported that EDs flow into sewage treatment plants, and it has been pointed out that these may be shifted from the wastewater treatment process to the sludge treatment process. Little is known about the fate of EDs accumulated in sewage sludge, so we carried out a study to clarify the fate of EDs in sewage sludge treatment processes, especially in an anaerobic digestion process. In this study, nonylphenol (NP) was selected as a target ED. Nonylphenol ethoxylates (NPnEO) or nonylphenoxy acetic acids (NPnEC), which were the precursor of NP, were added to an anaerobic digestion process, and mass balance was investigated. The following results were obtained from the anaerobic digestion experiments. (1) NP1EO was injected to an anaerobic digestion testing apparatus that was operated at a retention time of approximately 28 d and a temperature of 35 degrees C with thickened sludge sampled from an actual wastewater treatment plant. Approximately 40% of the injected NP1EO was converted to NP. (2) NP1EC was injected to an anaerobic digestion testing apparatus with thickened sludge. As a result, almost all injected NP1EC was converted to NP. When NP2EC was injected, NP2EC was not converted to NP until the 20th day.

Monitoring of di-(2-ethylhexyl)phthalate, nonylphenol, nonylphenol ethoxylates, and polychlorinated biphenyls in anaerobic and aerobic sewage sludge by gas chromatography–mass spectrometry

“…The nonylphenoxy acetic acids are finally decomposed to nonylphenol carboxylate [24], which could explain the smaller increase in the concentration of NP observed after the aerobic digestion (figure 4b) compared with that obtained after the anaerobic digestion (figure 4a), consistent with the study of Knudsen et al [23]. [19].…”

“…The concentration of the sum of NP, NP1EO, and NP2EO was considerably higher than the limit value of 50 mg kg À1 dm fixed in the third draft of the future European Sludge Directive in all samples analysed ( figure 3). It has been reported that under anaerobic conditions, NP2EO is degraded to NP1EO, and NP1EO is degraded to NP [23,24]. This fact explains the decrease in concentrations for NP1EO and NP2EO from primary and secondary sludge to anaerobically digested sludge (figure 4a) and the high concentration of NP in anaerobically digested sludge compared with the concentrations in primary and secondary sludge samples.…”

A Critical Review of the Formation of Mono- and Dicarboxylated Metabolic Intermediates of Alkylphenol Polyethoxylates during Wastewater Treatment and Their Environmental Significance

“…It was also postulated that increased NP concentrations may arise from NP 1 EO, which is anaerobically degraded even though these hydrophobic metabolites were released in small amounts. The study failed to identify the quantities of NPECs that can also anaerobically degrade to form NP (Minamiyama et al, 2006). The notion of NPECs contributing to the NP levels detected in the environment has been suggested by Conn et al (2006).…”

“…It is generally thought that NP 1 ECs is transformed to NP only under anaerobic conditions (Ahel et al, 1994a;Minamiyama et al, 2006) and anoxic conditions (Ike et al, 2002). Recently Liu et al (2006) reported the formation of NP from NP 2 EO with NP 1 EC and NP 2 EC as the intermediate metabolites, which were further transformed to shorter NPEOs under aerobic conditions by Ensifer sp.…”

Limitation of the concentration of organic pollutants in sewage sludge for agricultural purposes: A case study in South Spain

“…It has been reported that under anaerobic conditions NP2EO is degraded to NP1EO and NP1EO is degraded to NP (Knudsen et al, 2000;Minamiyama et al, 2006). This fact, together with the loss of weight achieved during the sludge dehydration process, explains the high concentration levels of NP in anaerobically-digested dehydrated sludge compared to the concentration levels in primary and secondary sludge samples and the decrease of the concentrations of NP1EO and NP2EO from primary and secondary sludges to anaerobically-digested dehydrated sludge (Table 2).…”