Jeff Kuo’s research while affiliated with California State University, Fullerton and other places

Water meter measurement error is considered as one important component of non-revenue water by International Water Association. Its magnitude depends combinedly on users’ consumption behaviors (intake spectrum) and metrological characteristics of water meters (meter error curve). Most published researches have only analyzed the meter error curves without taking the users’ consumption behaviors into consideration. This study developed a practical approach by using the relative difference chart of master-meters and sub-meters groupings (i.e., R M -μ z chart) to identify average metering errors for a major water utility company in Taiwan. About 120,000 sets of “master-meter and sub-meter grouping” data of Taipei Water Department were analyzed. The approach successfully estimated average metering errors of its 99.6% domestic meters (around 1.6 million water meters), the results are 9.9, 6.1, and 10.0% less than the actual water consumption recorded by the sub-meters, master-meters, and direct-meters, respectively.

Biodegradable plastics have been widely used to replace conventional plastics to minimize environmental impacts of plastic packaging. However, before biodegradable plastics decompose in the environment, they could pose a threat to terrestrial and aquatic creatures by acting as vectors of contaminants in the food chain. In this study, conventional plastic bags (CPBs) made of polyethylene and biodegradable plastic bags (BPBs) made of polylactic acid were examined for their heavy metal adsorption. Effects of solution pHs and temperatures on adsorption reactions were investigated. Because of a larger BET surface area, presence of oxygen-containing function groups, and smaller crystallinity, the heavy metal adsorption capacities of BPBs are significantly larger than those of CPBs. Among Cu (up to 791.48 mg⋅kg-1), Ni (up to 60.88 mg⋅kg-1), Pb (up to 1414.58 mg⋅kg-1), and Zn (up to 295.17 mg⋅kg-1), Pb and Ni show the largest and the lowest extents of adsorption onto the plastic bags, respectively. In the different waterbodies in nature, Pb adsorption on the CPBs and the BPBs were 318.08-379.91 and 528.41-764.22 mg⋅kg-1, respectively. Consequently, Pb was selected as the target contaminant in the desorption experiments. After Pb was adsorbed onto the CPBs and the BPBs, Pb could be completely desorbed and released into simulated digestive systems in 10 h. In conclusion, BPBs could be potential vectors of heavy metals, and their suitability as a substitute for CPBs must be thoroughly investigated and confirmed.

Water meter measurement error is considered as one important component of non-revenue water (NRW) by International Water Association (IWA). Its magnitude depends combinedly on users’ consumption behaviors (intake spectrum) and metrological characteristics of water meters (meter error curve). Most published researches have only analyzed the meter error curves without taking the users’ consumption behaviors into consideration. This study developed a practical approach by using the relative error chart of master-meters and sub-meters groupings (i.e., R M -chart) to identify average metering errors for a major water utility company in Taiwan. About 120,000 sets of “master-meter and sub-meter grouping” data of Taipei Water Department (TWD) were analyzed. The approach successfully estimated average metering errors of its 99.6% domestic meters (around 1.58 million water meters), the results are 9.85%, 6.11%, and 10% less than the actual water consumption recorded by the sub-meters, master-meters, and direct-meters, respectively.

Thermally-activated persulfate (PS) has been recognized as one of the most effective advanced oxidation processes (AOPs) to oxidize persistent perfluorooctanoic acid (PFOA). Applications of carbon aerogel (CA)-activated PS for PFOA decomposition at 25, 40, 50 and 60°C were evaluated. With the presence of CA in PS oxidation, 85.7% of PFOA was decomposed to fluoride ions and intermediates of short-chain perfluorinated carboxylic acids (PFCAs) with a 34.5% defluorination efficiency at 60°C after 8 h. PFOA was decomposed and mineralized to fluoride ions in the CA+PS system following a stepwise degradation process of C6F13COOH→C5F11COOH→C4F9COOH→C3F7COOH→C2F5COOH→CF3COOH at 60°C. The decomposition and defluorination rates of the combined CA+PS system at 60°C were approximately 1.83 and 1.61 times faster than those of the PS-only system, respectively. With CA in the PS system, activation energies of PFOA removal and defluorination were significantly reduced from 66.8 to 37.2 and 97.3 to 49.2 kJ/mol, respectively. It implies that applying CA could effectively promote the PFOA degradation that leads to significant savings in energy consumption and reductions in process time. Characteristics of CA used were evaluated by using N2 adsorption, zeta potential, Raman, SEM, XRD, XPS and FT-IR techniques. A quenching test was conducted by using methanol as an inhibitor and electron spin resonance (ESR) spectra of free radicals were analyzed for development of proposed reaction mechanisms.

Microplastics are frequently found in many environmental media. Polypropylene (PP) is one of the plastics commonly used, resulting in more and more PP fragments in natural waters. Contaminants, such as lead (Pb), could get adsorbed onto microplastics after the exposure to sunlight, and pose a larger threat to aquatic species. In this study, the oxidative indices of PP pellets after different exposure times to a Xenon lamp were evaluated by Fourier transform infrared (FTIR) and energy-dispersive X-ray spectrometry. The results show that the percentage of oxygen content increased from 2.80 to 20.95 wt% and changes of characteristic peaks of the FTIR pattern, implying that the exposure to the Xenon lamp could initiate oxidation. Due to the changes of functional groups after the exposure to the Xenon lamp for 28 days, the adsorption capacities of the PP pellets were up to 274.4 mg⋅kg⁻¹, 1.7 to 2.5 times higher than that of the raw PP pellets depending on the solution pHs. The adsorption behavior can be described by a pseudo-second-order model with rate constants of adsorption of 0.00212–0.01404 kg⋅mg⁻¹⋅h⁻¹. The increase of adsorption capacity due to changes of the PP pellets after the Xenon lamp exposure increased the potential risk to the aquatic species.

Using persulfate (PS) oxidation to remove the persistent perfluorooctanoic acid (PFOA) in water typically requires an elevated temperature or an extended reaction time. Under relatively ambient temperatures (15–45 °C), feasibility of employing PS with iron-modified activated carbon (AC) for PFOA oxidation was evaluated. With presence of Fe/AC in PS oxidation, 61.7% of PFOA was decomposed to fluoride ions and intermediates of short-chain perfluorinated carboxylic acids (PFCAs) with a 41.9% defluorination efficiency at 25 °C after 10 h. Adsorption of PFOA onto Fe/AC can be regarded as a pre-concentration step prior to subsequent oxidation of PFOA. Fe/AC not only removes PFOA through adsorption, but also activates PS to form sulfate radicals that accelerate the decomposition and mineralization of PFOA. With Fe/AC in the PS system, activation energies (Ea) of PFOA removal and defluorination were significantly reduced from 66.8 to 13.2 and 97.3 to 14.5 kJ/mol, respectively. It implies that PFOA degradation and defluorination could proceed at a lower reaction temperature within a shorter reaction time. Besides, the surface characteristics of AC and Fe/AC before and after PS oxidation were evaluated by XPS and SEM. A quenching test used MeOH as an inhibitor and EPR spectra of free radicals were conducted to develop the proposed reaction mechanisms for PFOA oxidation.