The effect of nitrification inhibitors on the aerobic biodegradation of tetracycline antibiotics in swine wastewater.

The aerobic biotreatment process for the dual goals of antibiotic removal and ammonia retainment for the field-return-based treatment of swine wastewater was optimized by adding 2-chloro-6-trichloromethylpyridine (TCMP), commonly used as a nitrogen fertilizer synergist. The results show that the dosage of 5-10 mg/L TCMP daily effectively inhibited nitrification. The COD and tetracycline antibiotics (TCs) in the absence of TCMP was removed by 91% and 76%, and became 87% and 78% with 5 mg/L TCMP and 83% and 70% with 10 mg/L TCMP, respectively. The removal efficiency of four TCs generally followed a decreasing trend of chlortetracycline (CTC) > doxycycline (DC) > tetracycline (TC) > oxytetracycline (OTC). A dosage of 5 mg/L TCMP daily inhibited ammonia nitrification effectively and only slightly affected the removal of conventional organic pollutants and TCs. The contribution of volatilization and hydrolysis to the removal of TCs was negligible. The overall removal efficiency of four TCs in removal pathway experiments was 98%, 94%, 97%, and 96% for OTC, CTC, DC, and TC, of which 69%, 41%, 56%, and 62% was contributed by absorption, and 29%, 53%, 41%, and 34% was contributed by biodegradation, respectively. This study may have significant implications for the proper management of livestock wastewater intended to be used as fertilizers, which aims to reduce the exposure risk of antibiotics and preserve its nutrient value.

Determination of estrogens and estrogen mimics by solid-phase extraction with liquid chromatography-tandem mass spectrometry.

An analytical method has been developed and validated for the determination of six estrogens and estrogen mimics, namely estriol (E3), bisphenol A (BPA), 17ß-estradiol (E2), estrone (E1), ethynyl estradiol (EE2) and dienestrol (DIE), with frequent occurrence in the natural environment. Solid phase extraction coupled with liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) using electrospray ionization (ESI) in a negative mode was applied to concentration, identification, and quantification of estrogens and estrogen mimics. The SPE conditions were optimized as the selection of C18 as cartridges and MeOH as an eluent, and the control of solution pH at 9.0. The method was validated by satisfactory recoveries (80-130%) and intra-day and inter-day precision (<18.4%, as relative standard deviation), and excellent linearity for calibration curves (R2 > 0.996). The limits of detection (LODs) for six target estrogenic compounds ranged between 2.5 and 19.2 ng/L. The effects of matrix background on the determination were evaluated in terms of LODs, LOQs, analyte recovery, and slopes of calibration curves in five different water matrices. Matrix effects by tap water were negligible. However, both matrix suppression and enhancement (i.e., E3, E1, DIE) were observed in surface water and wastewater. The positive correlation between LODs and TOC in various water matrices indicated the negative effect of organic pollutants on the method sensitivity. The sum of target estrogenic compounds in environmental samples were within 17-9462 ng/L.

The treatment of veterinary antibiotics in swine wastewater by biodegradation and Fenton-like oxidation.

Elevated concentrations and potential toxicities of antibiotics in swine wastewater prompt the exploration of effective treatment methods to minimize the amount of antibiotics released to the environment. This study examined the technical and economic feasibility of using combined biodegradation and advanced oxidation processes for swine wastewater treatment. The up-flow anaerobic sludge blanket (UASB) reactor was mainly responsible for conventional organic pollutant removal (i.e., a COD removal rate of 75%). The subsequent sequencing batch reactor (SBR) under a short sludge retention time (SRT) of 3 days removed the biodegradable antibiotics by >95%, and hindered the nitrification process which retained NH4+-N and reduced operational cost (since the treated wastewater was intended to be used as a farm fertilizer). The subsequent Fenton-like oxidation (with the aid of citric acid) achieved an average antibiotic removal efficiency of 74% under optimal reaction conditions: H2O2 dosage of 2.9 mM, [Fe2+]: [H2O2] = 1:3, [CA]: [Fe2+] = 1:1, pH 6.0, reaction time of 120 min. The superior treatment efficiency of Fenton-like compared to the conventional Fenton (74% vs 5%) under nearly neutral conditions was attributed to the chelating role of citric acid with Fe2+/Fe3+, leading to the enhanced Fe2+/Fe3+ solubility and therefore the promotion of ∙OH formation. This hybrid process of anaerobic and aerobic biodegradation and Fenton-like oxidation should be suitable and cost-effective for the treatment of wastewater with abundant conventional pollutants and persistent emerging trace contaminants.

Environmental occurrence and risk assessment of haloacetic acids in swimming pool water and drinking water.

A prevalent group of disinfection by-products (DBPs), i.e., haloacetic acids (HAAs), have raised significant public concern due to their high frequency of occurrence, considerable concentrations and potent toxicity. This study investigated the environmental occurrence of HAAs and the corresponding predicted human exposure to two important water matrices where humans are frequently and long-term exposed, i.e., swimming pool waters (SPWs) and drinking waters (DWs), in Shanghai, China. The sum of five HAAs in SPWs was 241 µg L-1 on average (dominated by dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA)), four times as much as its maximum contaminant level (MCL) regulated by the Environmental Protection Agency (EPA) in DWs. The maximum HAA concentration in DWs was 35 µg L-1, with chloroacetic acid (CAA) as the most dominant compound. The higher concentrations (reflected by total organic carbon (TOC), dissolved organic carbon (DOC), and UV254) and more categories (body fluids and personal care products in addition to natural organic matter) of organic contaminants and the higher chlorine in SPWs should be responsible for the differentiated HAA yield and speciation. The qualification rates of samples have been evaluated. The power function models correlating HAAs with multiple water quality parameters were developed with correlation coefficients of 0.614 and 0.798 for SPWs and DWs respectively. These models may provide the preliminary insights on how to minimize HAA formation by grasping the relative importance of each parameter and how to build the framework to predict HAA formation in untreated source water or SPWs subjected to chlorination. The predicted carcinogenic and non-carcinogenic risks of humans exposed to SPWs and DWs with HAAs were within the acceptable levels.

A hybrid process of Fe-based catalytic ozonation and biodegradation for the treatment of industrial wastewater reverse osmosis concentrate.

This work investigated the feasibility of a hybrid process consisting of catalytic ozonation and biodegradation (i.e., sequencing batch reactor, SBR) for the treatment of the industrial-based reverse osmosis concentrate (ROC) with specific characteristics of high levels of total dissolved solids (TDS) and refractory pollutants. The Fe-based homogeneous and heterogeneous catalytic ozonation was in parallel investigated and compared in terms of contaminant removal efficiency and biodegradability variation. The Fe-based heterogeneous catalyst carried the higher potential to improve the biodegradability of ROC (i.e., 0.32 v. s. 0.27 for B/C, the ratio between BOD5 and COD) although its direct COD removal efficiency was inferior to the homogeneous one (i.e., 49% v. s. 59% after 25 min' reaction). The ROC pretreated by the Fe-based heterogeneous catalytic ozonation for 5 min was further treated by biodegradation. After the hybrid treatment, the COD concentration reached ∼40 mg/L meeting with the discharge standard (GB, 18918-2002), under the optimal reaction conditions of 2.0 L/min ozone flow rate for catalytic ozonation and 120 min' aeration for biodegradation. The solution pH should not be adjusted by taking both the treatment efficiency and operating cost into consideration. The treatment cost of the hybrid process was estimated to be 0.15 USD/m3. This work could provide a feasible and economic option for the proper management of the industrial-based ROC and should be of interest to the application fields.