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Large-scale and rapid improvement in wastewater treatment is common practice in developing countries, yet this influence on nutrient regimes in receiving waterbodies is rarely examined at broad spatial and temporal scales. Here, we present a study linking decadal nutrient monitoring data in lakes with the corresponding estimates of five major anthropogenic nutrient discharges in their surrounding watersheds over time. Within a continuous monitoring dataset covering the period 2008 to 2017, we find that due to different rates of change in TN and TP concentrations, 24 of 46 lakes, mostly located in China’s populated regions, showed increasing TN/TP mass ratios; only 3 lakes showed a decrease. Quantitative relationships between in-lake nutrient concentrations (and their ratios) and anthropogenic nutrient discharges in the surrounding watersheds indicate that increase of lake TN/TP ratios is associated with the rapid improvement in municipal wastewater treatment. Due to the higher removal efficiency of TP compared with TN, TN/TP mass ratios in total municipal wastewater discharge have continued to increase from a median of 10.7 (95% confidence interval, 7.6 to 15.1) in 2008 to 17.7 (95% confidence interval, 13.2 to 27.2) in 2017. Improving municipal wastewater collection and treatment worldwide is an important target within the 17 sustainable development goals set by the United Nations. Given potential ecological impacts on biodiversity and ecosystem function of altered nutrient ratios in wastewater discharge, our results suggest that long-term strategies for domestic wastewater management should not merely focus on total reductions of nutrient discharges but also consider their stoichiometric balance.
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Critical evaluation of heat extraction temperature on soluble microbial products (SMP) and extracellular polymeric substances (EPS) quantification in wastewater processes
Abstract While soluble microbial products (SMP) and extracellular polymeric substances (EPS) in wastewater bioprocesses have been widely studied, a lack of standard quantification procedures make it difficult to compare results between studies. This study investigated the effect of temperature on SMP and EPS profiles for biological nutrient removal (BNR) sludges and aerobic membrane bioreactor sludge by adapting the commonly used heat extraction and centrifugation scheme, followed by colorimetric quantification of the carbohydrate and protein fractions using the phenol-sulfuric acid (PS) and the bicinchoninic acid (BCA) methods, respectively. To overcome known inconsistencies in colorimetry, total carbon (TC), total nitrogen (TN), and fluorometry analyses were performed in tandem. SMP samples marginally benefitted from heat extraction, owing to their mostly soluble nature, while EPS profiles were greatly influenced by temperature. 60 °C appears to be a suitable general-purpose extraction temperature near the lysis threshold for the sludges tested. The PS method's misestimation due to lack of specificity was observed and contrasted by TC analyses, while the TN analyses corroborated the BCA assays. Fluorometry proved to be a sensitive and rapid analytical method that provided semi-quantitative information on SMP and EPS constituents, particularly its proteinaceous components, with positive implications for robust wastewater process control.
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- Award ID(s):
- 1805631
- PAR ID:
- 10366575
- Publisher / Repository:
- DOI PREFIX: 10.2166
- Date Published:
- Journal Name:
- Water Science and Technology
- Volume:
- 85
- Issue:
- 8
- ISSN:
- 0273-1223
- Page Range / eLocation ID:
- p. 2318-2331
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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