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Globally, hundreds of millions of people still drink untreated surface water due to the lack of even a basic drinking water service, and urgently need economical off-grid water treatment devices. A passive, single-stage, permeate-side-heated solar thermal membrane distillation system is developed for extracting potable water from seawater, surface water, and municipal wastewater. The carbon black-coated permeate side of 0.45 µm PVDF membrane absorbs solar radiation and evaporates the feed water within the pores of the membrane. Under natural sunlight, the distillate flux was 8.56 kg/(m²∙day) at an average daytime irradiance of 652 W/m², equivalent to the system energy efficiency of 67.5%, the highest so far for single-stage solar distillation under natural sunlight. This system removed all the heterotrophic bacteria, 99.9% turbidity, and 99.6% chemical oxygen demand (COD) from wastewater, and reduced electrical conductivity by 99.9% from seawater, during the first 8 hours of operation under simulated sunlight (1800 W/m²). The operation continued for 32, 18, and 10 days on average for seawater, canal water, and wastewater, respectively, until the feed water penetrated the membrane. Throughout long-term experiments, distillate had decreasing flux within 0.98–1.55 kg/(m²∙h), steady pH of 7.2–7.9, steady turbidity of 0.09–0.21 NTU, steady electrical conductivity within 0.003–0.451 mS/cm, and increasing COD within 1.9–9.2 mg/L regardless of the type of feed water. Comprehensive water quality tests show that <a>the distillate extracted from all types of feed water meets U.S. drinking water standards for total coliform, 22 heavy metals and minerals, 7 anions, 5 physical factors, and 50 volatile organic compounds</a>, and will be safe to drink in real-world applications.

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Background Excess accumulation of heavy metals in frequently consumed food (e.g., vegetables, fruits) is a serious threat to human health. The concentration of heavy metals in four root vegetables and five leafy vegetables collected from the Kawran Bazar fresh vegetable market of Dhaka, Bangladesh, were analyzed. Average daily intake (ADI), hazard quotient (HQ), and hazard index (HI) were also estimated to assess the human health risks posed by the intake of heavy metals from the consumption of the studied vegetables. Apparent differences in the concentration of heavy metals present in different vegetables were observed. Results The presence and degree of contamination was assessed for chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn). Concentrations of Cr, Cd, Ni, and Cu exceeded the maximum permissible limit (MPL) in some root vegetables. Cr, Cd, Pb, Ni, Cu, Zn, and Fe concentration were higher in most studied leafy vegetables. ADI was found to be lower than the maximum permitted tolerable daily intake in most cases except Cr (0.202 mg/person day) and Fe (19.681 mg/person day) for the consumption of turnip and mint, respectively. Hazard quotient of Cr for turnip (1.121) and Zn for spinach (1.104), as well as the hazard indices of turnip (1.541), mustard (1.663), spinach (2.113), coriander (1.925), and mint (2.834), exceeded unit value, signifying potential health hazard from the dietary intake of the studied vegetables. Conclusions Higher concentrations of heavy metals were found in leafy vegetables compared to the root vegetables. Hence, the consumption of leafy vegetables has higher potential health risks than root vegetables. This study suggests that regular monitoring of heavy metals in vegetables is essential to prevent health risks associated with consuming heavy metal contaminated vegetables.

Globally, hundreds of millions of people still drink untreated surface water due to the lack of even a basic drinking water service and urgently need economical off-grid water treatment devices. A passive, single-stage, permeate-side-heated solar thermal membrane distillation system is developed for extracting potable water from seawater, surface water, and municipal wastewater. The carbon blackcoated permeate side of a 0.45 μm PVDF membrane absorbs solar radiation and evaporates the feedwater within the pores of the membrane. Under natural sunlight, the distillate flux was 8.56 kg/(m 2 •day) at an average daytime irradiance of 652 W/m 2 , equivalent to the system energy efficiency of 67.5%, the highest so far for single-stage solar distillation under natural sunlight. This system removed all the heterotrophic bacteria, 99.9% turbidity, and 99.6% chemical oxygen demand (COD) from wastewater and reduced electrical conductivity by 99.9% from seawater, during the first 8 h of operation under simulated sunlight (1800 W/m 2 ). The operation continued for 32, 18, and 10 days on average for seawater, canal water, and wastewater, respectively, until the feedwater penetrated the membrane. Throughout longterm experiments, the distillate had a decreasing flux within 0.98−1.55 kg/(m 2 •h), a steady pH of 7.2−7.9, a steady turbidity of 0.09−0.21 NTU, a steady electrical conductivity within 0.003−0.451 mS/cm, and an increasing COD within 1.9−9.2 mg/L regardless of the type of feedwater. Comprehensive water quality tests show that the distillate extracted from all types of feedwater meets U.S. drinking water standards for total coliform, 22 heavy metals and minerals, 7 anions, 5 physical factors, and 50 volatile organic compounds and will be safe to drink in real-world applications.

A systematic N 2 -based assay was developed to evaluate the denitrification kinetics of 23 different carbon sources, including C1−C8 organic acids in salt forms, alcohols, monosaccharides, and disaccharides under ambient anoxic conditions. The cumulative N 2 gas production volume was recorded in real time by respirometry for each carbon source through a series of denitrifying batch tests. Compared to the nitrate utilization rate (NUR) method for denitrification rate measurement, the N 2 -based assay was simple and easy to perform because of its real-time N 2 recording. By capturing all of the CO 2 using a KOH trap, no other gases such as H 2 and N 2 O were produced during the assay except for sucrose (0.002% N 2 O) as the carbon source. Acetate had the fastest specific denitrification rate (9.86 ± 1.00 mg-N/g volatile suspended solids (VSS)•h) among all of the carbon sources tested. Formate exhibited slower denitrification kinetics (2.82 ± 0.18 mg-N/g VSS•h) than most of the carbon sources tested, likely because few microorganisms could directly use this C1 chemical (valence of carbon = +2). The use of succinate resulted in incomplete denitrification as it inhibited microbial growth. Carbohydrates had relatively slow denitrification rates because they were used for denitrification and fermentation simultaneously, where possible metabolic pathways were proposed for producing volatile fatty acids such as propionate and valerate in addition to N 2 production. Glucose only had a maximum specific denitrification rate of 3.78 ± 0.09 mg-N/g VSS•h. Disaccharides had even slower denitrification kinetics (2.75− 3.43 mg-N/g VSS•h) than glucose, indicating that slow hydrolysis of disaccharides may be involved in denitrification.

Globally, hundreds of millions of people still drink untreated surface water due to the lack of even a basic drinking water service, and urgently need economical off-grid water treatment devices. A passive, single-stage, permeate-side-heated solar thermal membrane distillation system is developed for extracting potable water from seawater, surface water, and municipal wastewater. The carbon black-coated permeate side of 0.45 µm PVDF membrane absorbs solar radiation and evaporates the feed water within the pores of the membrane. Under natural sunlight, the distillate flux was 8.56 kg/(m²∙day) at an average daytime irradiance of 652 W/m², equivalent to the system energy efficiency of 67.5%, the highest so far for single-stage solar distillation under natural sunlight. This system removed all the heterotrophic bacteria, 99.9% turbidity, and 99.6% chemical oxygen demand (COD) from wastewater, and reduced electrical conductivity by 99.9% from seawater, during the first 8 hours of operation under simulated sunlight (1800 W/m²). The operation continued for 32, 18, and 10 days on average for seawater, canal water, and wastewater, respectively, until the feed water penetrated the membrane. Throughout long-term experiments, distillate had decreasing flux within 0.98–1.55 kg/(m²∙h), steady pH of 7.2–7.9, steady turbidity of 0.09–0.21 NTU, steady electrical conductivity within 0.003–0.451 mS/cm, and increasing COD within 1.9–9.2 mg/L regardless of the type of feed water. Comprehensive water quality tests show that <a>the distillate extracted from all types of feed water meets U.S. drinking water standards for total coliform, 22 heavy metals and minerals, 7 anions, 5 physical factors, and 50 volatile organic compounds</a>, and will be safe to drink in real-world applications.

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