Development of an internal two-stage upflow anaerobic reactor integrating biostimulation strategies to enhance the degradation of aromatic compounds in wastewater from purified terephthalic acid and dimethyl terephthalate manufacturing processes.

In this study, we aimed to establish high-rate biological treatment of purified terephthalic acid (PTA) and dimethyl terephthalate (DMT) wastewater that minimizes the inhibitory effects of high concentration benzoate and acetate. To achieve this, we developed a novel bioreactor system and biostimulation strategy. An internal two-stage upflow anaerobic (ITUA) reactor was operated with (i) a packed bed containing green tuff medium underlying (ii) a compartment seeded with anaerobic granular sludge. Ethylene glycol was amended to stimulate syntrophic interactions. Continuous operation of the system for 1,026 days achieve an organic removal rate of 11.0 ± 0.6 kg COD/m3/d. The abundance of aromatic degraders significantly increased during operation. Thus, we successfully developed a high-rate treatment system to treat wastewater from the PTA/DMT manufacturing processes by activating syntrophs in an ITUA reactor.

Long-term performance, membrane fouling behaviors and microbial community in a hollow fiber anaerobic membrane bioreactor (HF-AnMBR) treating synthetic terephthalic acid-containing wastewater.

Purified terephthalic acid (PTA) wastewater with properties of poor biodegradation and high toxicity is produced from refining and synthesis of petrochemical products. In this study, a lab-scale hollow fiber membrane bioreactor (HF-AnMBR) fed with synthetic PTA wastewater was operated over 200 days with stepwise decreased hydraulic retention time (HRT) to investigate the long-term performance, membrane fouling mechanism and microbial community evolution. Results showed that a stable chemical oxygen demand (COD) removal rate of 65.8 ± 4.1% was achieved at organic loading rate of 3.1 ± 0.3 g-COD/L-reactor/d and HRT 24 h, under which the methane production rate reached 0.33 ± 0.02 L/L-reactor/d. Further shortening HRT, however, led to the decreased COD removal efficiency and low methane bioconversion. A mild membrane fouling occurred due to the production of colloidal biopolymers and the interaction between increased colloidal substances secreted/cracked by microorganisms and membrane interface. Further 16S rRNA analysis indicated that microbial diversity and richness had changed with the variation of HRT while Methanosaeta, and Methanolinea species were always the dominant methanogens responsible for methane production. The results verify that HF-AnMBR is an alternative technology for PTA wastewater treatment along with energy harvesting, and provide a new avenue toward sustainable petrochemical wastewater management.

Improved purified terephthalic acid wastewater treatment using combined UAFB-SBR system: At mesophilic and ambient temperature.

In this study, a combined UAFB-SBR process was introduced to improve the treatment efficiency of PTA wastewater. The techno-economic feasibility of the process was evaluated in terms of organic removal efficiencies under mesophilic (37 °C) and ambient temperature (15-25 °C) during the long-term run. The lab-scale study revealed that all organic compounds present in the PTA wastewater could be efficiently removed under both mesophilic and ambient temperature, and p-toluic acid is probably the critical pollutant regulating the overall process performance in anaerobic stage, which should be seriously considered. The Miseq Sequencing results suggested that, along with the system temperature variation from mesophilic to ambient temperature, greater effects on bacterial community than archaeal community were detected in the UAFB reactor, while only slight variations were observed in the SBR reactor. Further taxonomy analysis demonstrated that within the UAFB reactor, the syntrophic partnership of Syntrophorhabdus, Syntrophus and Desulfovibrio with hydrogenotrophic methanogens were the main impetus for aromatic organics reduction. In the meanwhile, the intensively identified Thauera and Azoarcus groups were speculated of important roles in the aerobic degradation of aromatic compounds.

Influence of organic loading rate on purified terephthalic acid wastewater treatment in a temperature staged anaerobic treatment (TSAT) system: Performance and metagenomic characteristics.

In this study, a temperature staged anaerobic treatment (TSAT) system featured by thermophilic reactor (R1)-mesophilic reactor (R2) co-digestion was introduced to treat PTA wastewater. The process was successively conducted at three organic loading rates (OLRs): 3.34, 4.45, 6.68 kg COD/(m³·d), respectively (OLRs were R1 basis). The results indicated that TSAT system was highly efficient in PTA wastewater treatment at OLR lower than 4.45 kg COD/(m³·d). Miseq sequencing analysis demonstrated that R1 and R2 were predominated by hydrogenotrophic Methanolinea and acetotrophic Methanosaeta, separately. In addition, TA06, Caldisericia and Acetothermia associated groups were highly abundant in R1, whereas Chlorobiaceae and Syntrophobacteraceae were largely observed in R2. Tax4Fun analysis suggested that the important functional capabilities were significantly different between R1 and R2 (P < 0.05). The pathways related to aromatic compounds degradation mainly occurred in mesophilic stage, while the biosynthesis and metabolism pathways were more favored in thermophilic stage.

Impacts of biostimulation and bioaugmentation on the performance and microbial ecology in methanogenic reactors treating purified terephthalic acid wastewater.

Up-flow anaerobic sludge blanket (UASB) processes treating purified terephthalic acid (PTA) wastewater often face challenges associated with biomass loss. As excessive biomass loss could lead to deterioration of PTA removal, biostimulation and bioaugmentation were often practiced without understanding the microbial impact in UASB. Three laboratory-scale UASB reactors were operated with synthetic PTA wastewater as the feed, with two added with co-substrate (glucose or molasses) on Day 170 for 90 days, and one with external granules on Day 118. Throughout the operation, treatment performance was measured together with the analysis of microbial communities of biomass samples using 16S rRNA-based gene Illumina sequencing. Glucose amendment destabilized both terephthalic acid and para-toluic acid removal, while molasses amendment improved para-toluic acid removal. Both substrate addition generally led to decreases in the abundances of syntrophs and methanogens and increases in carbohydrate-fermenting bacteria in the granular sludge. Regarding bioaugmentation, paper mill granule addition led to a temporary crash of terephthalic acid removal for 42 days, and deterioration of para-toluic acid removal throughout the operation. Syntrophs and methanogens were observed to colonize on the paper mill granules after three months, meanwhile growth of methanogens were stimulated on the PTA granules added initially. Overall, proper level of molasses amendment and external granule inoculation could be promising strategies to make up for biomass loss during the operation of PTA-degrading UASB.

Performance of a single chamber microbial fuel cell at different organic loads and pH values using purified terephthalic acid wastewater.

BACKGROUND: Purified terephthalic acid (PTA) wastewater from a petrochemical complex was utilized as a fuel in the anode of a microbial fuel cell (MFC). Effects of two important parameters including different dilutions of the PTA wastewater and pH on the performance of the MFC were investigated. METHODS: The MFC used was a membrane-less single chamber consisted of a stainless steel mesh as anode electrode and a carbon cloth as cathode electrode. Both power density and current density were calculated based on the projected surface area of the cathode electrode. Power density curve method was used to specify maximum power density and internal resistance of the MFC. RESULTS: Using 10-times, 4-times and 2-times diluted wastewater as well as the raw wastewater resulted in the maximum power density of 10.5, 43.3, 55.5 and 65.6 mW m(-2), respectively. The difference between the power densities at two successive concentrations of the wastewater was considerable in the ohmic resistance zone. It was also observed that voltage vs. initial wastewater concentration follows a Monod-type equation at a specific external resistance in the ohmic zone. MFC performance at three different pH values (5.5, 7.0 and 8.5) was evaluated. The power generated at pH 8.5 was higher for 40% and 66% than that for pH 7.0 and pH 5.4, respectively. CONCLUSIONS: The best performance of the examined MFC for industrial applications is achievable using the raw wastewater and under alkaline or neutralized condition.