Assessing the efficiency of constructed wetlands in removing PPCPs from treated wastewater and mitigating the ecotoxicological impacts.

The prevalence of pharmaceuticals and personal care products (PPCPs) in municipal wastewater has led to increased concerns about their impact on both human health and ecosystem. The constructed wetlands have been recognized as one of the cost-effective and green mitigation approaches to remove the PPCPs in the municipal wastewater. In this study, the effectiveness of a full scale constructed wetlands treatment system (CCWTs) in removing the 36 PPCPs was investigated. The load mass of PPCPs discharged by the wastewater treatment plant into the CCWTs was calculated. Removal efficiencies of PPCPs were evaluated based on physico-chemical properties such as octanol-water partition coefficient (Log kow), molecular weight (MW, g mol-1) and the acid dissociation constant (pKa). The CCWTs are especially efficient in removing azithromycin, sertraline, tolfenamic acid, and diphenhydramine with removing efficiency >88%. However, the removal efficiencies of PPCPs in CCWTs exhibit a large variability, depending on physical and chemical properties of the molecules, with 4.7-96.7% for antibiotics, 5-86% for antidepressant and antiseizure drugs, 3.5-88% for NSAIDs, 29-77% for ß-blockers and statins and 5.5-94% for other types of PPCPs. In addition, the environmental risk assessment showed that majority of the PPCPs (excluding sulfamethoxazole) in the effluent yielded low aquatic risk (risk quotient, RQ ≤ 0.1) due to the efficiency of CCWTs. The toxicity index scores were calculated by integration of the predicted and available toxicological hazard data into the prioritization ranking algorithm through Toxicological Prioritization Index (ToxPi).

Evaluation of thirteen haloacetic acids and ten trihalomethanes formation by peracetic acid and chlorine drinking water disinfection.

Free chlorine is a commonly used disinfectant in drinking water treatment. However, disinfection by-products (DBPs) are formed during water disinfection. Haloacetic acids (HAAs) and trihalomethanes (THMs) are two major groups of DBPs. Iodo-HAAs and iodo-THMs (I-HAAs and I-THMs) are formed during the disinfection of the water containing high levels of iodide and are much more toxic than their chlorinated and brominated analogs. Peracetic acid (PAA) is a strong antimicrobial disinfectant that is expected to reduce the formation of HAAs and THMs during disinfection. In this study, the formations of thirteen HAAs and ten THMs, including the iodinated forms, have been investigated during PAA disinfection and chlorination as the comparison. The DBP formations under different iodide concentrations, pHs, and contact times were systematically investigated. Two types of commercial PAAs containing different concentrations of PAA and hydrogen peroxide (H2O2) were studied. A solid-phase microextraction gas chromatography-mass spectrometry method was upgraded for THM analysis including I-THMs. HAAs were analyzed by following a recently developed high performance ion chromatography-tandem mass spectrometry method. Results show that the ratio of PAA and H2O2 concentration significantly affect the formation of I-THMs and I-HAAs. During PAA disinfection with lower PAA than H2O2, no detectable levels of THMs and HAAs were observed. During PAA disinfection with higher PAA than H2O2, low levels of monoiodoacetic acid, diiodoacetic acid, and iodoform were formed, and these levels were enhanced with the increase of iodide concentration. No significant quantities of chloro- or bromo-THMs and HAAs were formed during PAA disinfection treatment.