Municipal wastewater treatment with pond technology : historical review and future outlook

Facing an unprecedented population growth, it is difficult to overstress the assets for wastewater treatment of waste stabilization ponds (WSPs), i.e. high removal efficiency, simplicity, and low cost, which have been recognized by numerous scientists and operators. However, stricter discharge standards, changes in wastewater compounds, high emissions of greenhouse gases, and elevated land prices have led to their replacements in many places. This review aims at delivering a comprehensive overview of the historical development and current state of WSPs, and providing further insights to deal with their limitations in the future. The 21st century is witnessing changes in the way of approaching conventional problems in pond technology, in which WSPs should no longer be considered as a low treatment technology. Advanced models and technologies have been integrated for better design, control, and management. The roles of algae, which have been crucial as solar-powered aeration, will continue being a key solution. Yet, the separation of suspended algae to avoid deterioration of the effluent remains a major challenge in WSPs while in the case of high algal rate pond, further research is needed to maximize algal growth yield, select proper strains, and optimize harvesting methods to put algal biomass production in practice. Significant gaps need to be filled in understanding mechanisms of greenhouse gas emission, climate change mitigation, pond ecosystem services, and the fate and toxicity of emerging contaminants. From these insights, adaptation strategies are developed to deal with new opportunities and future challenges

Greenhouse gas emissions from municipal wastewater treatment facilities in China from 2006 to 2019

Wastewater treatment plants (WWTPs) alleviate water pollution but also induce resource consumption and environmental impacts especially greenhouse gas (GHG) emissions. Mitigating GHG emissions of WWTPs can contribute to achieving carbon neutrality in China. But there is still a lack of a high-resolution and time-series GHG emission inventories of WWTPs in China. In this study, we construct a firm-level emission inventory of WWTPs for CH4, N2O and CO2 emissions from different wastewater treatment processes, energy consumption and effluent discharge for the time-period from 2006 to 2019. We aim to develop a transparent, verifiable and comparable WWTP GHG emission inventory to support GHG mitigation of WWTPs in China

Can constructed wetlands be more land efficient than centralized wastewater treatment systems? A case study based on direct and indirect land use

Compared with centralized wastewater treatment systems, constructed wetlands are generally regarded as not suitable for wide deployment due to the comparatively larger direct land area. Much of the traditional thinking is based on an onsite perspective, while the offsite information is left out. By a comparative case study with systems accounting of both onsite and offsite land use, this study questioned the traditional picture and found that constructed wetlands can be more land use efficient than centralized wastewater treatment systems. On a unit of wastewater treated basis, the land use induced by a typical constructed wetland in China is revealed to be less than half of that by the case of a centralized wastewater treatment plant or a hybrid system. On a unit removal basis for biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solid (TSS) and ammonia‑nitrogen (NH3−N), the land use induced by a constructed wetland is only around 61%, 67%, 73% and 64% of that by a centralized wastewater treatment system, respectively. Meanwhile, the indirect effect is demonstrated to be significant for these three systems: this magnitude amounts to three times the direct land occupation for a constructed wetland, and one order of magnitude higher of that for the a centralized wastewater treatment system. By a scenario analysis for China in 2017, it is preliminarily estimated that over two billion square meters of land use could be reduced if all the centralized wastewater treatment systems are replaced by constructed wetlands. The outcome may serve a benchmark and offers a new way of thinking for management of wastewater treatment systems

A novel aerated surface flow constructed wetland using exhaust gas from biological wastewater treatment: Performance and mechanisms

© 2017 In this study, a novel aerated surface flow constructed wetland (SFCW) using exhaust gas from biological wastewater treatment was investigated. Compared with un-aerated SFCW, the introduction of exhaust gas into SFCW significantly improved NH4+-N, TN and COD removal efficiencies by 68.30 ± 2.06%, 24.92 ± 1.13% and 73.92 ± 2.36%, respectively. The pollutants removal mechanism was related to the microbial abundance and the highest microbial abundance was observed in the SFCW with exhaust gas because of the introduction of exhaust gas from sequencing batch reactor (SBR), and thereby optimizing nitrogen transformation processes. Moreover, SFCW would significantly mitigate the risk of exhaust gas pollution. SFCW removed 20.00 ± 1.23%, 34.78 ± 1.39%, and 59.50 ± 2.33% of H2S, NH3 and N2O in the exhaust gas, respectively. And 31.32 ± 2.23% and 32.02 ± 2.86% of bacterial and fungal aerosols in exhaust gas were also removed through passing SFCW, respectively

A cost benefit analysis for the denitrification of waste water utilizing wetlands versus wastewater treatment facilities

The purpose of this project was to not only identify current regulatory issues, as they pertain to water and denitrification, but also could be used to assist policy makers with identifying other factors to be considered when choosing the appropriate advanced treatment systems for their facilities

Greenhouse gas emissions associated with urban water infrastructure:What we have learnt from China's practice

Municipal water and wastewater services have complicated sources of greenhouse gas (GHG) emissions, and quantifying their roles is critical for tackling global environmental challenges. In this study we provide a systematic review of the state-of-the-art on GHG emission characterizations of China's urban water infrastructure with the aim of shedding light on global implications for sustainable development. We started by synthesizing a framework on GHG emissions associated with water and wastewater infrastructure. Then we analyzed the different sources of GHG emissions in drinking water and wastewater treatment systems. In drinking water services, electricity consumption is the largest source of GHG emissions. A particular concern in China is the common use of secondary pumping for high-rise buildings. Optimized pressure management with an efficient pumping system should be prioritized. In wastewater services, non-CO 2 emissions such as methane (CH 4) and nitrous oxide (N 2O) emissions are substantial, but vary greatly depending on regional and technological differences. Further research directions may include GHG inventory development for urban water systems at the plant level, quantifications of GHG emissions from sewer systems, emission reduction measures via water reclamation, renewable energy recovery, energy efficiency improvement, cost–benefit analyses, and characterizations of Scope 3 emissions. This article is categorized under: Engineering Water &gt; Sustainable Engineering of Water Science of Water &gt; Water and Environmental Change Engineering Water &gt; Planning Water. </p

Modeling Greenhouse Gas Emissions from Conventional Wastewater Treatment Plants in South Carolina

Wastewater treatment is an essential part of life in the urbanized world. As global climate change becomes a more pressing issue, the greenhouse gas emissions created through wastewater treatment will become a more prominent concern. Tertiary treatment will likely be standard for wastewater treatment plants in the near future, and therefore must be included in a model of greenhouse gas emissions. Also, the geographic location of a WWTP will change the mix of power types (e.g., coal, nuclear, biomass) used to run the plant. Although GHG emissions from the waste sector are small compared to the emissions of the United States as a whole, they should still be managed and reduced. CO2e-WWTP, the model produced, is based largely on the work of Monteith et al. (2005) and was written using Visual Basic within Microsoft Excel to allow for a simple user interface. Modifications included removing a fitting factor for solids, generating a method for estimating the amount of nitrous oxide produced, and allowing for the calculation of greenhouse gas emissions from power from different sources. Eleven wastewater treatment plants, having capacities of 0.5 to 2.5 million gallons per day, were modeled for emissions of carbon dioxide, methane, and nitrous oxide. The plants were modeled with their current treatment systems and with the addition of tertiary treatment such as activated carbon, rapid sandfiltration, and an activated lagoon/wetland. The average carbon dioxide equivalent emissions for the treatment processes were found to be 0.410 g/L. It was found that in conventional wastewater treatment systems that nitrous oxide production does not contribute significantly to overall greenhouse gas emissions (about 2-4% of carbon dioxide equivalent emissions), however, when solids treatment is considered nitrous oxide emissions are a more significant contribution (about 4-13% of carbon dioxide equivalent emissions). Several of the power sources created GHG emissions that were statistically different from the other power sources found through the use of an ANOVA. Greenhouse gas emissions from wastewater treatment processes and plants can vary greatly depending on the processes employed which is why CO2e-WWTP is a valuable tool for those both in academia and the wastewater treatment field. However, more field research into wastewater treatment and its mechanisms for producing GHG emissions needs to be done.