Table 3 Summary of some studies conducted for biological removal of PAEs

Anaerobic/anoxic/oxic (AAO) treatment system

DMP

The optimal HRT and SRT for DMP and nutrients removal were 18 h and 15 days, respectively, and the degradation rates of anaerobic, anoxic and aerobic zones for DMP were 13.4, 13.0, and 67.7%, respectively

The biodegradation process of DMP by the selected method was in accordance with the first-order kinetics model. Under the optimal conditions, about 73.8, 5.8, 19.3, and 1.1% of DMP was biodegraded, released in the effluent, accumulated in the system, and remained in the waste sludge, respectively

[60]

Trickling filter

DEP and DEHP

Trickling filter achieved 94–99% of DEP and 44% of DEHP removal

DEHP was the most recalcitrant among the selected phthalates and DEP with less molecular weight was biodegraded with higher rate

[61]

Cyclic activated sludge technology (CAST), anoxic/oxic (AO), and anaerobic/anoxic/oxic (AAO) processes

DEP, DMP, DnBP, BBP, DEHP and DOP

The overall removal efficiency of all the selected PAEs was more than 72% in CAST while AO and AAO only achieved about 30% of PAEs removal

The better performance of the CAST process was attributed to its better indoor-conditions for bacterial community

[62]

Moving bed biofilm reactor (MBBR)

DAP and DEP

In optimum conditions with HRT of 9 h, about 95 and 94% of DEP and DAP were removed, respectively. In addition, more than 92% of COD removal was achieved for both phthalates

MBBR tolerated both of the selected phthalates with the influent concentrations of 100–300 mg L⁻¹. Sludge yield constants (Y) varied from 0.3 to 0.54. The maximum specific growth rates were 0.37 and 0.34 day⁻¹ for DEP and DAP, respectively

[8]

Up-flow anaerobic sludge blanket reactor (UASB)

DMP

More than 99% of DMP and 93% of COD were removed from the wastewater containing 600 mg L⁻¹ of DMP (corresponding to 3 g COD L⁻¹ day⁻¹) of organic loading rate of) at 8 h of HRT

The sludge yield was estimated as 0.08 g VSS g COD⁻¹. DMP was first de-esterified to mono-methyl phthalate (MMP) and, then, to phthalate (or phthalic acid) and, subsequently de-aromatized and converted into methane and CO₂. The maximum specific degradation rates of DMP, MMP, and phthalate were 415, 88, and 36 mg (g VSS day)⁻¹, respectively

[63]

Anaerobic/anoxic/oxic treatment system (AAO)

DnBP

The optimal HRT and SRT for DnBP removal were 18 h and 15 days, respectively. In the mentioned conditions, about 72.66% of DnBP was degraded by the selected process, 24.44% was accumulated in the system, 2.44% was released in the effluent, and 0.5% remained in the waste sludge

Increasing SRT from 10 to 15–25 days resulted in increasing removal efficiency from 90 to 95%. Higher SRT improved DnBP biodegradation efficiency. The removal efficiencies of anaerobic, anoxic and oxic reactors were 17.14, 15.02, and 63.46% of the total DnBP removal, respectively

[64]

Submerged membrane bioreactor (aerobic condition)

DEHP

The removal efficiency of DEHP under HRTs of 4 and 6 h, SRT of 140 days, and sludge concentration of 11.5 and 15.8 g VS L⁻¹ ranged between 91 and 98%

The removal of DEHP was closely dependent on the membrane pore size and about 74% of inlet DEHP was biodegraded

[65]