Journal of Environmental Engineering

Fouling control and operation below critical fluxes are relevant for operating membrane bioreactors (MBRs). Within this study, the long-term performance of a pilot-scale MBR was characterized with the aim of achieving maximum operating time without chemical cleaning. The MBR was fed with the effluent from a full-scale anaerobic reactor from a brewery and, combined with an upstream flotation unit, the MBR reduced chemical oxygen demand by 93.6%. During operation, the permeate flux was varied and a dependency of the fouling rate on permeate flux was found, which was not affected by the fluctuations caused by treatment with real wastewater. The fouling was controlled by intermittent 1-min relaxation phases followed by 4-min filtration. Applying this method, the MBR was operated at a flux of $9.5–11.5\mathrm{L}/({\mathrm{m}}^2\mathrm{h})$ and a fouling rate below $0.06\mathrm{kPa}/\mathrm{day}$ for 329 days without chemical cleaning until the permeability decreased by $>50\%$ to $0.8\mathrm{L}/({\mathrm{m}}^2\mathrm{h}\mathrm{kPa})$. Based on monitoring the relaxation phases alone, a sudden increase in blockage was found by Day 280, while transmembrane pressure and permeability readings continued without registering major variation for more than 40 days later. This early indication is in industrial scale of special importance because it can be used as an additional method for detecting fouling.

The International Ultraviolet Association (IUVA) recommended a method to measure the ultraviolet (UV) output of monochromatic (254 nm) UV lamps. In that method, the lamp is operated in open air and it is not applicable to the underwater UV lamp because temperature influences the UV output of a UV lamp. In this work, a method to measure the UV output of a UV lamp inside a quartz sleeve that is fully immersed in water was established. First, the quartz sleeve was set to be partially immersed in water and the UV output was determined by the IUVA method for a lamp in open air. Second, the measured value was modified by the ratio of the measured relative UV outputs in the cases that the lamp and quartz sleeve was fully and partially immersed in water. The measurement outcome was the UV emission from the quartz sleeve, which is the concern in UV application, rather than that from the lamp. When applying the measurement method, it is key to control the water level to be lower than a threshold. A formula to calculate the threshold of the water level was derived.

The transport of virus-laden particles was investigated numerically in an archetypical supermarket configuration of area ${\mathrm{1,200}\mathrm{m}}^2$ and ceiling height of $4.5\mathrm{m}$. The particles were tracked using a Lagrangian particle tracking code coupled with the computational fluid dynamics (CFD) model Ansys Fluent. Air transport was assumed to occur due to indoor ventilation. Flow dynamics were simulated using the Reynolds-averaged Navier Stokes (RANS) approach. The movement and spreading of 5- and $20\text{-}\mathrm{\mu m}$ particles were studied with 0%, 25%, and 100% attachment efficiencies on surfaces in the supermarket. We found that the indoor airflows can significantly enhance the transport of particles (e.g., $>15\mathrm{m}$ for $5\mathrm{\mu m}$, and $>5\mathrm{m}$ for $20\mathrm{\mu m}$); therefore, the $6\text{-}\mathrm{ft}$ ($2.0\mathrm{m}$) social distance recommended by health experts would not be sufficient to prevent the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We found that the attachment on surfaces reduces the transport of particles significantly within the supermarket, and that an attachment efficiency of 25% results in transport similar to that resulting from 100% efficiency. This suggests that the type of surfaces is not crucial in terms of air transport of particles. We support the existing approaches for reducing exposure between people through the adoption of one-way movement within an aisle. However, we also propose placing display shelves within the aisles in a staggered way to form baffles that would both increase the surface area and block the transport of airborne particles. We found that virus-laden particles could be sucked into the ventilation system through return vents, and could pose potential infection risks for the buildings connected to the same ventilation system. Hence, high-efficiency particulate air (HEPA) filters and pleated filters with a minimum efficiency reporting value (MERV) greater than 12 are recommended.

Since the 1990s, a major Australian water agency has monitored the concentrations of Cryptosporidium and Giardia in eight tributaries to its principal water supply reservoir. The accumulated data have recently been made available for analysis, resulting in this paper. The eight catchments total over $\mathrm{7,700}{\mathrm{km}}^2$ ($\sim \mathrm{3,000}{\mathrm{mi}}^2$) producing an average of approximately 1,800 ML/day (475 mgd) of water treated downstream to supply a population of nearly 4 million. Beginning in 2002, weekly 10 L samples from each of the eight sites were analyzed. Significantly, recovery efficiency of both organisms was measured for every sample. Data analyzed in this project encompassed all samples from 2002 through 2014. Data were analyzed to identify chronological variations in the concentration of both organisms and in terms of cumulative frequency analysis. These analyses permitted the identification of differences in concentration patterns related to catchment characteristics, including identification of temporal patterns related to season or weather, estimation of the most common (median) concentrations, and the degree of variation typical of each sampling location. Clear differences were apparent between typical concentrations and variabilities among the eight stations. Giardia concentrations were characteristically higher than Cryptosporidium. The data clearly illustrate the continuous long-term presence of Cryptosporidium and Giardia, despite the many nondetect analytical results. The concentrations and variabilities of both organisms were in the midrange of what has been reported at locations throughout the US. These comparisons, made possible by measurement of true concentration by including recovery efficiency measurement for every sample, will form the basis for further investigation of individual catchment characteristics and conditions in an effort to account for differences in observed concentration patterns.

Bioretention media plays a vital role in bioretention systems for controlling rainfall runoff volume and removing pollutants. In this work, three different types of modified media used in bioretention including a mixture of river sand, soil, biochar, and volcanic (BV), and BVS (BV + iron-coated sand) were assessed. To evaluate the purification efficiency, the removal of total nitrogen (TN), total phosphorus (TP), ammonium (${\mathrm{NH}}_4^{+}–\mathrm{N}$), and chemical oxygen demand (COD) in rainfall runoff were measured under different rainfall intensities and antecedent dry times (ADTs). As a result, the bioretention system with BVS was more beneficial to the removal of TP under variable ADT and rainfall intensity. The bioretention system with BVZ possessed much better performance in TN removal, which was more than 2.2 times that of BV and BVS, and lower nitrogen leaching during long ADT due to its great affinity for nitrogen. All three bioretention systems have better removal efficiency of ${\mathrm{NH}}_4^{+}–\mathrm{N}$ during a longer ADT for the occurrence of nitrification. The three bioretention systems also exhibited excellent COD removal that could even reach over 95% after the microorganisms multiplied. Based on the analytic hierarchy process (AHP) with cost, purification, and infiltration, the comprehensive performances of modified media were as follows: $\mathrm{BVZ}(0.926)>\mathrm{BV}(0.723)\text{\hspace{0.17em}>\hspace{0.17em}}\mathrm{BVS}(0.696)$.

Food waste has become an increasing concern across the globe. Anaerobic digestion (AD) has been recognized as an effective approach for handling this waste while generating biogas. AD’s performance could be enhanced by improving the carbon conversion efficiency and leading to the lowest amount of residuals possible. For this purpose, various pretreatment approaches have been investigated. This study focuses on optimizing thermal pretreatment of food waste. In particular, three parameters, namely temperature, treatment time, and total solid content, were evaluated statistically for their effects on the increase of soluble chemical oxygen demand (SCOD). It was found that temperature and time had statistically significant impacts on the SCOD increase compared with the untreated controls. The optimal condition of 170°C, 60 min, and $118\mathrm{g}/\mathrm{L}$ solid content led to a 1.92-fold increase of SCOD. After a 5-day fermentation, the pretreated slurries produced $17.1\mathrm{g}/\mathrm{L}$ of volatile fatty acids. Results from this study could be used at large scale for pretreating food waste before AD for producing biogas or other valuable products.

During outbreaks, contaminated surfaces can contribute to the spread of cholera; as such, surface disinfection with chlorine is widely recommended. However, confirmation of surface disinfection efficacy against Vibrio cholerae requires testing for the V. cholerae bacteria, which is not commonly completed in outbreak settings. We investigated whether culturable Escherichia coli (commonly measured in outbreak settings) is an appropriate surrogate for culturable V. cholerae by conducting experiments using 0.02% chlorine made with sodium dichloroisocyanurate (NaDCC) on six nonporous and porous surfaces. Across all test conditions, culturable E. coli were reduced by 1.3 to $>6.9\log$ and culturable V. cholerae by 4.9 to 7.0 log. Results suggest culturable E. coli is a conservative surrogate for culturable V. cholerae, and it is recommended that E. coli can be used in households and health care facilities in cholera outbreaks as a conservative indicator of adequate disinfection. Further research is recommended on the relative importance of fomite transmission in cholera contexts, the role that viable but nonculturable (VBNC) V. cholerae (not tested herein) might have in transmission, and potential surrogates for VBNC V. cholerae.