Tracking pollutants in a municipal sewage network impairing the operation of a wastewater treatment plant.

This work provides a screening of organic contaminants and characterization of the dissolved organic matter in the sewer network until the municipal wastewater treatment plant (WWTP), identifying the network areas with a higher degree of contamination and their impact on the WWTP performance, particularly in the activated sludge reactor. Three monitoring campaigns were carried out at six selected locations of the sewage system (PVZ-1, PVZ-2, PS-F, PS-VC, CP-VC, and PS-T), influent (WWTPINF) and effluent (WWTPEFF) of the WWTP. Advanced analytical techniques were employed, namely excitation/emission matrix fluorescence-parallel factor analysis (EEM-PARAFAC), size exclusion chromatography with organic carbon detector (SEC-OCD), and liquid chromatography with high-resolution-mass spectrometric detection (LC-HRMS). EEM-PARAFAC showed higher fluorescence intensity for the protein-like component (C2), particularly at CP-VC (near seafood industries) associated with the presence of surfactants (~50 mg/L). SEC-OCD highlighted the WWTP efficiency in removing low molecular weight acids and neutrals. LC-HRMS tentatively identified 108 compounds of emerging concern (CEC) and similar detection patterns were obtained for all wastewater samples, except for PVZ-2 (lower detection), many of which occurred in the effluent. Eight CECs included on relevant Watch-Lists were detected in all WWTPEFF samples. Furthermore, 111 surfactants were detected, the classes more frequently found being alcohol ethoxylates (AEOs), nonylphenol polyethoxylates (NPEOs) and linear alkylbenzene sulphonates (LAS). The continuous presence of LAS and NPEOs allied to surfactants concentrations in the WWTPINF of 15-20 mg/L, with CP-VC location (linked with food industries) as an important contributor, explain the morphological changes in the activated sludge and high LAS content in the dewatered sludge, which may have impacted WWTP performance.

Bromate removal from water intended for human consumption by heterogeneous photocatalysis: Effect of major dissolved water constituents.

This study focuses on the influence of major dissolved constituents naturally found in waters intended for human consumption on bromate (BrO3-) reduction by heterogeneous photocatalysis. The individual and combined effect of chloride (Cl-), bicarbonate/carbonic acid (HCO3-/H2CO3), nitrate (NO3-), sulphate (SO42-) and humic acids (HAs) on BrO3- reduction was evaluated in synthetic waters (SWs). Additionally, freshwaters (FWs) from a drinking water treatment plant (DWTP) were tested and directly compared to SWs. Cl- was beneficial for contents in the range 0.47-1.4 mM, with negligible influence for lower and higher contents. NO3- had a null effect regardless of its content (0.024-0.81 mM). HCO3-/H2CO3 (0.061/0.45 mM), SO42- (0.12-2.6 mM) and HAs (0.11-1.0 mM C) had a negative effect in the tested contents. The BrO3- reduction rate was 2.8 times lower in SW with a mixture of water constituents compared to SW without constituents addition. This decline on BrO3- reduction rate corresponded to the sum of the individual species contribution and so there was no evidence of synergetic effects. By contrast, the use of FWs provided BrO3- reduction rates only slightly lower than that found for SW without constituents addition (∼1.2-fold), which can be attributed to: (i) the distinct characteristics of the organic matter of FWs (HAs, fulvic acids and humins with distinct molecular weights and functional groups) compared to that of SW (pure HAs), and/or (ii) the presence in FWs of other inorganics in addition to those here addressed. The heterogeneous TiO2 photocatalysis proved to be a promising process for BrO3- reduction in DWTPs.