Sustainable production in circular economy: aerogel upscaling production

Environmental Science and Pollution Research -     

Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers

In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with ¹³C and ¹⁵N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60 days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44 % after 60 days, respectively, and about 22 and 43 % of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60 days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.     

Spectroscopic Distribution of Dissolved Organic Matter in a Dam Reservoir Impacted by Turbid Storm Runoff

Spectroscopic characteristics of dissolved organic matter (DOM) in a large dam reservoir were determined using ultraviolet absorbance and fluorescence spectroscopy to investigate spatial distribution of DOM composition after turbid storm runoff. Water samples were collected along a longitudinal axis of the reservoir at three to four depths after a severe storm runoff. Vertical profiles of turbidity data showed that a turbid water layer was located at a middle depth of the entire reservoir. The spectroscopic characteristics of DOM samples in the turbid water layer were similar to those of terrestrial DOM, as demonstrated by the higher specific UV absorbance (SUVA) and the lower fluorescence emission intensity ratio (F ₄₅₀/F ₅₀₀) compared to other surrounding DOM samples in the reservoir. Synchronous fluorescence spectroscopy revealed that higher content of humic-like DOM composition was contained in the turbid water. Fluorescence excitation–emission matrix (EEM) showed that lower content of protein-like aromatic amino acids was present in the turbid water DOM. The highest protein-like fluorescence was typically observed at a bottom layer of each sampling location. The bottom water DOM exhibited extremely high protein-like florescence near the dam site. The particular observation was attributed to the low water temperature and the isolation of the local bottom water due to the upper location of the withdrawal outlet near the dam. Our results suggest that the distribution of DOM composition in a dam reservoir is strongly influenced by the outflow operation, such as selective withdrawal, as well as terrestrial-origin DOM inputs from storm runoff.     

Effects of mineral surfaces on pyrene partitioning to well-characterized humic substances

Mineral surfaces can alter the ability of humic substances (HS) to bind hydrophobic organic contaminants. In this study, complete adsorption (i.e., to avoid HS adsorptive fractionation effects) of a small subset of well-characterized terrestrial and aquatic HS on kaolinite and hematite significantly changed their subsequent organic carbon-normalized partition coefficients K(ads)(oc) for pyrene relative to their original respective dissolved organic carbon-normalized partition coefficients K(dis)(oc). Parallel experiments with ultrafiltration (UF) fractions obtained from purified Aldrich humic acid (PAHA) (Aldrich Chemical, Milwaukee, WI) gave similar results. The heterogeneity among the PAHA UF fractions was examined via their mineral surface adsorption characteristics and their subsequent ability to bind pyrene. As expected, variations in maximum adsorption densities (q(max)), Langmuir adsorption constants (K(q)), and pyrene K(ads)(oc) values were observed among the PAHA UF fractions. However, general trends of q(max), K(q), and pyrene log K(ads)(oc) values for the PAHA UF fractions versus the logarithm of their weight-average molecular weights (MW(w)) did not typically match the corresponding trends obtained with the four aquatic and terrestrial HS. In general, an ideal mixture competitive adsorption model gave reasonable predictions for PAHA sorption to kaolinite and hematite based on their corresponding UF isotherm parameters. Ideal mixture predictions of pyrene partitioning to adsorbed PAHA from the corresponding UF fraction results were better for kaolinite versus hematite, indicating that the underlying mineral surface can alter the effects of HS heterogeneity on hydrophobic organic contaminant sorption.     

Assessing microbial and chemical exposure risks of Giardia in indoor swimming pool water disinfected by chlorine

Swimming pools adopt chlorination to ensure microbial safety. Giardia has attracted attention in swimming pool water because of its occurrence, pathogenicity, and chlorine resistance. To control Giardia concentrations in pool water and reduce the microbial risk, higher chlorine doses are required during disinfection. Unfortunately, this process produces carcinogenic disinfection byproducts that increase the risk of chemical exposure. Therefore, quantitatively evaluating the comparative microbial...     

Importance of nutrient availability for soluble microbial products formation during a famine period of activated sludge: Evidence from multiple analyses

Much remains unknown about compositional variations in soluble microbial products (SMP) with the shift of the substrate condition from a feast to a famine phase in biological treatment systems. This study demonstrated that the formation of SMP could be suppressed by up to 75% during the famine phase with the addition of essential nutrients. In contrast, presence of electron acceptor did not play any significant role during the stress condition, showing the similar amounts of SMP (r?=?0.98, p?<?0.05) formation between the bioreactors supplied with air and N₂. The SMP formed in the famine phase was more bio-refractory in the famine versus the feast phase with a linear correlation shown between the production and their aromatic structures in the composition (R²?>?0.95). The fluorescence excitation–emission matrix coupled with parallel factor analysis (EEM-PARAFAC) revealed the presence of four different fluorescent components, including two protein-like (C1 and C4), fulvic-like (C2), and humic-like (C3) components, in the SMP and bEPS formed at different conditions. Both C1 and C4 showed increasing trends (R²?>?0.95) with the length of starvation in the bioreactors without essential nutrients. Nutrient availability was found to be a key factor to quench the production of large-sized biopolymers. This study provides a wealth of information on operation conditions of activated sludge treatment systems to minimize large sized SMP molecules (particularly proteins), which typically exert many environmental concerns to effluent organic matter quality.