Removal of bis (2-ethylhexyl) phthalate from reject water in a nitrogen-removing sequencing batch reactor

Role of treatment configuration in simultaneous removal of priority phthalic acid esters and nitrogen in a post anoxic integrated biofilm activated sludge system

To develop future wastewater treatment systems, focus is to improve/investigate existing biological wastewater treatment processes for the concurrent treatment of conventional pollution parameters (essentially nitrogen) and micro pollutants. Majority of the existing biological wastewater treatment systems were not designed for the removal of micro pollutants. This study focuses on understanding the role of treatment configuration for efficient removal of nitrogen and priority phthalic acid esters (PAEs) from real municipal wastewater in an integrated biofilm activated sludge (IBAS) system. The reactor was operated in two phases: Run I, without external carbon source in anoxic reactor and Run II, a nitrogen removal process, with partial diversion of untreated wastewater in anoxic reactor. Nitrogen removal was 70 ± 12% in both operational phases, however, during Run I, removal of PAEs fluctuated with an average removal of 60-78%. Comparatively, removal of PAEs in Run II varied over a smaller range with average removal increased to 89-95%. In both operational scenarios, secondary oxic tank contributed maximum to the overall removal of PAEs in treatment system. Mass balance calculations showed significant contribution of biodegradation towards overall removal of PAEs which was enhanced by the supply of external carbon source. Kinetics and model output supported the PAEs removal performance observed in different reaction environments of IBAS process. A correlation between food to microorganism (F/M) ratio and PAEs removal showed increase in PAEs removal with decrease in F/M ratio. The study showed that treatment configuration and F/M ratio may be one of the guiding parameters for efficient removal of PAEs in biological wastewater treatment.

An overview of phthalate acid ester pollution in China over the last decade: Environmental occurrence and human exposure

The toxicity and bioaccumulation potential of phthalate acid esters (PAEs) make their impact on the environment a matter of considerable concern. Due to China's recent economic development and population growth, it has become one of the largest manufacturers and consumers of PAEs, with an associated contamination threat to several environmental compartments. The aim of this overview is to present a systematic account of PAE occurrence in various environmental media in China in the last decade, including the air, surface water, sediments, soil, sewage, and sludge; human exposure to PAEs is also evaluated. This reveals a location-dependence that can be attributed to regional differences in economic and industrial development as well as specific geographic location. A need for further study into the transportation and transformation behavior of PAEs in different environmental media and into PAE control technologies is identified, as a means of effectively assessing potential ecological and health risks.

Adsorption of Phthalates on Municipal Activated Sludge

Phthalates (PAEs) are commonly detected in discharge of municipal wastewater treatment plants. This study investigated the removal of six typical PAEs with activated sludge and the results revealed that concentrations of aqueous PAEs decreased rapidly during the beginning 15 min and reached equilibrium within 2 hours due to the adsorption of activated sludge. The process followed first-order kinetic equation, except for dioctyl phthalate (DOP). The factors influencing the adsorption were also evaluated and it was found that higher initial concentrations of PAEs enhanced the removal but affected little the adsorption equilibrium time. The adsorption of PAEs favored lower operating temperature (the optimum temperature was approximately 25°C in this research), which could be an exothermic process. Additionally, lower aqueous pH could also benefit the adsorption.

A comparative study of occurrence and fate of endocrine disruptors: diethyl phthalate and dibutyl phthalate in ASP- and SBR-based wastewater treatment plants

Phthalates are endocrine-disrupting chemicals which affect endocrine system by bio-accumulation in aquatic organisms and produce adverse health effects in aquatic organisms as well as human beings, when come in contact. Present study focuses on occurrence and removal of two phthalates: diethylphthalate (DEP) and dibutylphthalate (DBP) in two full-scale wastewater treatment plants (WWTPs) i.e. sewage treatment plants (STPs) based on well-adopted technologies, activated sludge process (ASP) and sequencing batch reactor (SBR).Gas chromatography-mass spectrometry (GC-MS) analysis was performed for both wastewater and sludge sample for determination and identification of the concentration of these compounds in both STPs by monitoring the STPs for 9 months. It was observed that the concentration of DEP was less than DBP in the influent of ASP and SBR. Average concentrations of DEP and DBP in sludge sample of ASP were found to be 2.15 and 2.08 ng/g, whereas in SBR plant, these values were observed as 1.71 and 2.01 ng/g, respectively. Concerning the removal efficiency of DEP, SBR and ASP plants were found effective with removal efficiency of 91.51 and 91.03 %, respectively. However, in the case of DBP, SBR showed lower removal efficiency (85.42 %) as compared to ASP (92.67 %). Comparative study of both plants proposed that in ASP plant, DBP reduction was higher than the SBR. Fourier transformation infrared (FTIR) analysis also confirmed the same result of sludge analysis for both STPs. Sludge disposal studied with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermo-gravimetric analysis (TGA) techniques confirmed that sludge of both STPs have high calorific value and can be used as fuel to make fuel-briquettes and bottom ash to make firebricks.

Occurrence and fate of endocrine disrupting chemicals in ASP based sewage treatment plant in Hardwar

The occurrence of emerging contaminants such as endocrine disrupting chemicals (EDCs) in our water resources is of prime concern. With this context, fate and seasonal variation of six EDCs (testosterone, T; progesterone, P; diethyl phthalate, DEP; dibutyl phthalate, DBP; propyl-paraben, PP and butyl-paraben, BP) were assessed throughout the year, i.e. in rainy, winter, spring and summer seasons in the raw, treated wastewater and activated sludge in an activated sludge process (ASP) based sewage treatment plant (STP) located in Haridwar, India. Qualitative and quantitative measurements were performed by gas chromatography-mass spectrometry (GC-MS) analysis. Results indicate that in summer, the examined STP could effectively remove 82.9% of T, 86.4% of P, 95.5% of DEP, 92.4% of DBP, 91.5% of PP, and 89.9% of BP from the wastewater. Among the EDCs considered, higher removal efficiencies were achieved for phthalates in the summer season. GC-MS analysis showed that a small fraction of EDCs was sorbed on the solid fraction of activated sludge. Scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transformation infrared spectroscopy analysis were also performed to investigate the occurrence of EDCs in biomass samples. Results of this study also demonstrated that removal efficiency, assessed in terms of physicochemical and microbiological parameters, was maximum in summer and reached minimum in rainy season.

Simultaneous removal of di-(2-ethylhexyl) phthalate and nitrogen in a laboratory-scale pre-denitrification biofilter system

This study demonstrated the excellent di-(2-ethylhexyl) phthalate (DEHP) removal performance of a pre-denitrification biofilter system. Experimental results showed that DEHP removal efficiency remained stable while total nitrogen removal efficiency fluctuated with the nitrate recycle ratio changes when the hydraulic loading rate at 1.1m(3)/m(2)h. DEHP removal efficiency increased from 48% to 82% while the hydraulic loading rate increased from 1.1 to 2.2m(3)/m(2)h. DEHP concentration decreased gradually along the wastewater flow direction in the denitrification biofilter and a plug flow model with the reaction order of 5 and the rate constant of 0.54 was obtained. Both the denitrification biofilter and the nitrification biofilter showed similar DEHP removal performance. The overall DEHP removal efficiency of the system was 83.8%, in which biodegradation contributed 72.3%. Biodegradation plays a key role in DEHP removal in the pre-denitrification biofilter system.

Occurrence and fate of phthalate esters in full-scale domestic wastewater treatment plants and their impact on receiving waters along the Songhua River in China

The occurrence and fate of six phthalates: dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP) were investigated as phthalates passed through three full-scale wastewater treatment plants (WWTPs) with different treatment processes, and ultimately into the recipient Songhua River water in Harbin (China). The six phthalates were detected in the majority of aqueous and solid samples, with DEHP being the most abundant compound. The overall removal efficiency of ΣPAEs in the Cyclic Activated Sludge Technology (CAST) process was over 72%, while both the A/O and A/A/O processes achieved approximately 30% removal. The better performance of the CAST process relative to the Anoxic/Oxic (A/O) and Anaerobic/Anoxic/Oxic (A/A/O) processes was attributed to the indoor-conditions of the CAST plants, which effectively maintained the temperature of the treatment system. The fate of PAEs within two different types of WWTPs (CAST and A/A/O) were assessed qualitatively using mass balances. The results suggested that PAEs removal resulted from both biotransformation and adsorption, of which the former was particularly significant in the CAST process, while the latter was more significant in the A/A/O process. Substantial levels of several PAEs were detected in the Songhua River, especially downstream of the WWTPs, which means that the discharge from WWTPs has a strong impact on the water quality of the Songhua River during cold winter conditions.

The importance of the suspended solids parameter on the quantitative analysis of di-n-butyl phthalate in a wastewater treatment system

The present study has investigated the influence of the filtration step of the liquid-liquid extraction (LLE) on the quantitative analysis of di-n-butyl phthalate (DnBP) in the wastewater treatment system of the University of Caxias do Sul (WWTS-UCS). During five months, five wastewater samples from the inflow and outflow points were collected and submitted to LLE with and without the filtration step. The organic extracts were analyzed by Gas Chromatography with Flame Ionization Detection (GC/FID). The DnBP removal in the filtered samples was 36%, and the median DnBP concentration at the outflow point was 17.45 μg/mL. For the unfiltered samples, the DnBP removal was 39%, and the median DnBP concentration at the outflow point was 21.45 μg/mL. According to these results, an important fraction of the contaminant is retained in the LLE filtration step leading to considerable errors in the quantification of the target compounds.

An assessment of the levels of phthalate esters and metals in the Muledane open dump, Thohoyandou, Limpopo Province, South Africa

BACKGROUND

This work reports the determination of the levels of phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), diethyl hexyl phthalate (DEHP)) and metals (lead, cadmium, manganese, zinc, iron, calcium) in composite soil samples. The soil samples were collected randomly within the Muledane open dump, Thohoyandou, Limpopo province, South Africa. Control samples were collected about 200 m away from the open dump. The phthalate esters were separated and determined by capillary gas chromatography with a flame ionization detector, whilst the metals were determined by atomic absorption spectrophotometry.

RESULTS

Open dump values for the phthalate esters and metals to be generally higher in comparison to control samples for DMP, DEP, DBP and DEHP - the mean values calculated were 0.31 +/- 0.12, 0.21 +/- 0.05, 0.30 +/- 0.07, and 0.03 +/- 0.01 mg/kg, respectively, for the open dump soil samples. Nonetheless, the mean open dump values for lead, cadmium, manganese, zinc, iron and calcium were 0.07 +/- 0.04, 0.003 +/- 0.001, 5.02 +/- 1.92, 0.31 +/- 0.02, 11.62 +/- 9.48 and 0.12 +/- 0.13 mg/kg, respectively. The results were compared statistically.

CONCLUSION

Our results revealed that the discarding of wastes into the open dump is a potential source of soil contamination in the immediate vicinity and beyond, via dispersal. Increased levels of phthalate esters and metals in the soil pose a risk to public health, plants and animals. Sustained monitoring of these contaminants is recommended, in addition to upgrading the facility to a landfill.