Sewer blockages and overflows have significant economic and environmental repercussions on communities. Thus, it is crucial to detect and remove sewer blockages prior to the occurrence of overflows. With the improvement in mobile networks and the development of high-quality and low-power sensors and loggers, wastewater network operators can now adopt monitoring devices enabled by the "Internet of Things" (IoT) technology for real-time monitoring. To this end, this paper studies the current state-of-the-art in sewer blockage management and introduces a novel methodology to monitor sanitary sewer blockages to prevent sanitary sewer overflows (SSO) with the least human interaction. The proposed system incorporates low-power level sensors and 4G telemetry for real-time monitoring of the manhole's sewage level to detect sewer blockages. The blockage detection methodology encompasses a set of decision rules and time series analysis to identify blockage events. The final blockage detection model offers a versatile capability to be implemented on sanitary sewer networks of different types with minimum computational costs.

Estimating wastewater treatment plants’ (WWTPs) influent parameters such as 5-day biological oxygen demand (BOD5) and chemical oxygen demand (COD) is vital for optimizing electricity and energy consumption. Against this backdrop, the existing body of knowledge is bereft of a study employing Artificial Intelligence-based techniques for the prediction of BOD5 and COD. Thus, in this study, Gene expression programming (GEP), multilayer perception neural networks, multi-linear regression, k-nearest neighbors, gradient boosting, and regression trees -based models were trained for predicting BOD5 and COD, using monthly data collected from the inflow of 7 WWTPs over a three-year period in Hong Kong. Based on different statistical parameters, GEP provides more accurate estimations, with R2 values of 0.784 and 0.861 for BOD5 and COD respectively. Furthermore, results of sensitivity analysis undertaken by monte Carlo simulation revealed that both BOD5 and COD were mostly affected by concentrations of total suspended solids, and a 10% increase in the value of TSS resulted in a 7.94% and 7.92% increase in the values of BOD5 and COD, respectively. It is seen that the GEP modeling results complied with the fundamental chemistry of the wastewater quality parameters and can be further applied on other sewage sources such as industrial sewage and leachate. The promising results obtained pave the way for forecasting the operational parameters during sludge processing, leading to an extensive energy savings during the wastewater treatment processes.

Sewer overflow contains several hazardous contaminants causing adverse health effects and annoyance to the public. Despite this importance, few studies has hitherto been undertaken on examining the odor nuisance and risk of diseases due to contact with untreated overflow. However, quantitative investigation of odor emission from the sanitary sewage overflows has not been addressed. As such, this study aims to scrupulously investigate the deleterious impact of such phenomenon on public health in terms of the aforesaid matters. To this end, a multi-stage methodological approach was employed. Firstly, field data was collected from the vicinity of a wastewater treatment plant for three years, and then the concentrations of H2S in the aqueous phase and gaseous phase were estimated based on the environmental parameters. Afterward, the Gaussian aerial dispersion model and Quantitative Microbial Risk Assessment (QMRA) were employed. In parallel, the impact of the exposure to the malodorous H2S emitted from overflow cases was assessed. Furthermore, the results obtained from impact assessment were validated using the developed questionnaire survey. From the results obtained, the following major conclusions are drawn: (1) levels of H2S(g) near the overflow were high enough to be perceived by individuals, (2) concentrations of NH3(g) in the ambient air were estimated lower than the perception threshold, (3) the sulfide concentration in the overflow was the most influential parameter with positive linear correlation with the concentration of H2S(g), (4) the concentration of odor causes high annoyance, according to the questioning from the residents near the overflow events (5) exponential dose-response indicated 89–95% infection risk and (6) the good correlation between the estimated values of annoyance and the real annoyance level perceived by the residents proved accuracy of the methodology for estimation of H2S concentration and annoyance level. The unique findings obtained from this study guide the environmental decision-makers to take pre-emptive actions, preventing risk of infection and complaints from the residents.

This study systematically revealed the feasibility of the sequential ClO2-UV/chlorine process for micropollutant removal and disinfection byproduct (DBP) control. The results demonstrated that the sequential ClO2-UV/chlorine process was effective for the removal of 12 micropollutants. ClO2 pre-treatment reduced the formation of disinfect byproducts (DBPs) in the UV/chlorine process. Compared to the UV/chlorine process, ClO2 pre-treatment (1.0 mg L−1) decreased the formation of the 6 DBPs by 25.1–72.2%; and decreased the formation potential of the 6 DBPs by 13.9–51.8%. Moreover, ClO2 pre-treatment reduced the concentration of total organic chlorine by 19.8%. ClO2 pre-treatment affected the UV/chlorine process in different ways. Firstly, ClO2 pre-treatment generated chlorite, which dominantly served as a scavenger of chlorine radical (Cl) and hydroxyl radical (HO). Secondly, ClO2 pre-treatment decreased the reactivity of natural organic matter (NOM) towards radicals. Finally, ClO2 pre-treatment altered the properties of NOM, in terms of reducing the electron-donating capacity and aromaticity of NOM (SUVA254), and slightly reducing the average molecular weight of NOM. Overall, ClO2 pre-treatment effectively controlled the formation of DBPs in the UV/chlorine process. This study confirmed the sequential ClO2-UV/chlorine process was an alternative strategy to balancing the micropollutant removal and DBP control.

The need in using reclaimed water increased significantly to address the water shortage and its continuing quality deterioration in sustaining societal development. Degrading micropollutants in wastewater treatment plant effluents is one of the most important tasks in supplying safe drinking water, which is often achieved by full advanced treatment technologies (FATs), including reverse osmosis (RO) and the UV-based advanced oxidation process (AOP). As an emerging AOP, UV/chloramine process shows many noteworthy advantages in the scenario of potable water reuse, including membrane biological fouling control by chloramine, producing highly reactive radicals (e.g., Cl-center dot, HO center dot, Cl-2(center dot-), and reactive nitrogen-containing species) to degrade the RO permeated pollutants, and acting as long-lasting disinfectant in the potable water distribution system. In addition, chloramine is often designedly produced by taking advantage of the ammonia in source. Thus, UV/chloramine processes gather much attention from researcher and published papers on UV/chloramine process have drastically increased since 2016, which were thoroughly reviewed in this paper. The fundamentals of chloramine photolysis, including the photolysis kinetics, the quantum yield, the generation and transformation of radicals and the final products, were scrutinized. Further, the impacts of reaction conditions such as pH, chloramine dosage and water matrix on the degradation of micropollutants by the UV/chloramine process are discussed. Moreover, the formation potential of disinfection by-products is debated. The opportunity of application of the UV/chloramine process in real-world practice is also presented, emphasizing the need for extensive efforts to remove currently prevalent knowledge roadblocks.

This study systematically revealed the feasibility of the sequential ClO2-UV/chlorine process for micropollutant removal and disinfection byproduct (DBP) control. The results demonstrated that the sequential ClO2-UV/chlorine process was effective for the removal of 12 micropollutants. ClO2 pre-treatment reduced the formation of disinfect byproducts (DBPs) in the UV/chlorine process. Compared to the UV/chlorine process, ClO2 pretreatment (1.0 mg L-1) decreased the formation of the 6 DBPs by 25.1-72.2%; and decreased the formation potential of the 6 DBPs by 13.9-51.8%. Moreover, ClO2 pre-treatment reduced the concentration of total organic chlorine by 19.8%. ClO2 pre-treatment affected the UV/chlorine process in different ways. Firstly, ClO2 pretreatment generated chlorite, which dominantly served as a scavenger of chlorine radical (Cl center dot) and hydroxyl radical (HO center dot). Secondly, ClO2 pre-treatment decreased the reactivity of natural organic matter (NOM) towards radicals. Finally, ClO2 pre-treatment altered the properties of NOM, in terms of reducing the electron-donating capacity and aromaticity of NOM (SUVA(254)), and slightly reducing the average molecular weight of NOM. Overall, ClO2 pre-treatment effectively controlled the formation of DBPs in the UV/chlorine process. This study confirmed the sequential ClO2-UV/chlorine process was an alternative strategy to balancing the micropollutant removal and DBP control. (C) 2021 Elsevier B.V. All rights reserved.

Ultraviolet (UV)/chlorine processes are emerging advanced oxidation processes (AOPs) for micropollutant abatement. When excessive chlorine (Cl/N mass ratio of >7.6) is applied to ammonia-containing water to yield free chlorine residual for the UV/ free chlorine AOP, the AOP becomes UV/breakpoint chlorination. This study investigated micropollutant degradation by and radical yields from UV/breakpoint chlorination under various conditions using benzoic acid (BA) and nitrobenzene (NB) as representative micropollutants and radical probes. Two stages of degradation were observed. During stage I, BA and NB were rapidly degraded; this was attributed to the reactive species generated from breakpoint chlorination (R-brk) and UV photolysis of chlor(am)ines and breakpoint chlorination intermediates/products (R-pho). During stage II, the degradation followed pseudo-first-order kinetics, and UV photolysis of unknown irreducible residuals produced from breakpoint chlorination greatly contributed to generating reactive species, in addition to UV photolysis of free chlorine. At pH 7 and an ammonia concentration of 1 mg/L as N, an optimum chlorine dosage for micropollutant degradation existed at 9.6 mg/L as Cl-2 due to the strong scavenging from excessive free chlorine. The findings demonstrate that UV/breakpoint chlorination is a promising approach for degrading refractory micropollutants in realworld applications.

This study compares the influences of UV/chlorine and UV/H2O2 advanced oxidation of natural organic matter at the equivalent degradation of two model micropollutants on the formation of disinfection by-products (DBPs) and toxicity during post-chlorination. At 90% degradation of carbamazepine, the UV/chlorine advanced oxidation process (AOP) at pH 6.0 (3.0 mg/L chlorine and 280 mJ/cm(2)) resulted in comparable yields of dichloroacetic acid, trichloroacetic acid, chloroform, chloral hydrate, dichloroacetonitrile, trichloropropanone and total organic chlorine (TOCl) during the post-chlorination, compared to the UV/H2O2 AOP (8.0 mg/L H2O2 and 280 mJ/cm(2)). The UV/chlorine AOP increased the chloroacetic acid yields by 28-43% at pH 7.0 and 8.0. The cytotoxicity with the UV/chlorine AOP was 32% lower than with the UV/H2O2 AOP, however, the genotoxicity was similar. At the 90% degradation of atrazine, the UV/chlorine AOP (6.0-13.9 mg/L chlorine and 750-1000 mJ/cm(2)) increased the chloroacetic acid yields by 35-81% but did not increase the yields of other four known DBPs and TOCl, compared to the UV/H2O2 AOP (8.0-12.9 mg/L chlorine and 750-1000 mJ/cm(2)). The cytotoxicity and genotoxicity with the UV/chlorine AOP at pH 6.0 were 22-27% lower than those with the UV/H2O2 AOP, likely due to the selective destruction of the precursors of cytotoxic and genotoxic DBPs by RCS. The TOCl yields were positively correlated to the decreases in the specific UV absorbance at 254 nm and humic-like fluorescence. The TOCl yields exhibited a linear relationship with the genotoxicity (R-2 = 0.81) but were weakly correlated with the cytotoxicity (R-2 = 0.40). Although the UV/chlorine AOP increases the formation of some DBPs under certain circumstances, compared to the UV/H2O2 AOP, it does not enhance the genotoxicity and even decreases the cytotoxicity.

The formation of disinfection by-products (DBPs) from the degradation of N,N-diethyl-3-methyl benzoyl amide (DEET) and ibuprofen (IBP) by the ultraviolet irradiation (UV)/chlorine process and subsequent post-chlorination was investigated and compared with the UV/H2O2 process. The pseudo first-order rate constants of the degradation of DEET and IBP by the UV/chlorine process were 2 and 3.1 times higher than those by the UV/H2O2 process, respectively, under the tested conditions. This was due to the significant contributions of both reactive chlorine species (RCS) and hydroxyl radicals (HO) in the UV/chlorine process. Trichloromethane, 1,1,1-trichloro-2-propanone and dichloroacetic acid were the major known DBPs formed after 90% of both DEET and IBP that were degraded by the UV/chlorine process. Their yields increased by over 50% after subsequent 1-day post-chlorination. The detected DBPs after the degradation of DEET and IBP comprised 13.5% and 19.8% of total organic chlorine (TOCl), respectively, and the proportions increased to 19.8% and 33.9% after subsequent chlorination, respectively. In comparison to the UV/H2O2 process accompanied with post-chlorination, the formation of DBPs and TOCl in the UV/chlorine process together with post-chlorination was 5%-63% higher, likely due to the generation of more DBP precursors from the attack of RCS, in addition to HO.

The short life span of electrical and electronic equipments (EEE) produces a tremendous amount of waste electrical and electronic equipments (WEEE) globally at an overwhelming rate. Currently, the recycling of waste printed circuit board (WPCB) is an emerging and sensitive environmental issue since traditional treatment methods have been proved to be inappropriate. Also, the recovery of valuable components from WPCB is limited by the environmental emissions from the recycling process, which have been seriously neglected by the research community before. To analyze the environmental emission impacts and set evaluation criteria, a newly developed aluminosilicate adsorbent production process is discussed in this work. It is proved to be capable to recycle the NMF of WPCB as the feedstock of the functionalization process. Besides, the mass balance of reaction reagents, bromide and carbon were established with clear pathways and destinations by various analytical chemistry methods. The debromination process in functionalization significantly reduced the total toxicity by giving inorganic bromide and bisphenol A (BPA) as two main products. The results confirm this process to be an environmentally friendly process which can provide a basis for evaluating recycling processes.

The removal of BTEX (benzene, toluene, ethyl-benzene and p-xylene) from contaminated groundwater was evaluated by paper mill sludge-based activated carbon, prepared by chemical activation and pyrolysis.The effects of pH, time, adsorbent dosage and adsorbate concentration were studied through batch adsorption experiments. Selected physical and chemical characteristics of the adsorbents, such as specific surface area (613m2/g), pore volume distribution (micropore: 277cm3/g, mesopore: 365cm3/g) and surface functional groups (carboxylic, alkyl and aliphatic groups) were determined by N2 adsorption-desorption diagram and FTIR, respectively. The removal efficiency of the four target compounds would be more than 92 %, which the initial concentrations of BTEX and the adsorbent dosage were 40 mg/l and 1000 mg/l, respectively. It was proved that pH and ionic strength have insignificant effects on the adsorption efficiency. The order of adsorption amount in all experiments was > ethyl-benzene > toluene > benzene. The kinetic data proved a closer fit to the pseudo-first-order model. The isotherm experimental data showed a better fit to either Freundlich or Langmuir model. In addition, a series of experiments was conducted to evaluate the capacity of the adsorbent in adsorbing the BTEX from a groundwater sample contaminated with gasoline.