Next Article in Journal
Estimation of CN Parameter for Small Agricultural Watersheds Using Asymptotic Functions
Previous Article in Journal
Exploring the Modifiable Areal Unit Problem in Spatial Water Assessments: A Case of Water Shortage in Monsoon Asia
Article Menu

Export Article

Open AccessArticle
Water 2015, 7(3), 918-938; doi:10.3390/w7030918

Carbon Footprint Analyses of Mainstream Wastewater Treatment Technologies under Different Sludge Treatment Scenarios in China

1
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, No. 73 Huanghe Road, Nangang District, Harbin 150090, China
2
School of Marine Science and Technology, Harbin Institute of Technology at Weihai, No. 2 Wenhua West Road, High-tech New District, Weihai 264209, China
3
School of Chemical Engineering and Technology, Harbin Institute of Technology, No. 92 West Dazhi Street, Nangang District, Harbin 150001, China
4
Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong
*
Authors to whom correspondence should be addressed.
Academic Editor: Miklas Scholz
Received: 10 December 2014 / Revised: 7 January 2015 / Accepted: 19 February 2015 / Published: 5 March 2015
View Full-Text   |   Download PDF [463 KB, uploaded 9 June 2015]   |  

Abstract

With rapid urbanization and infrastructure investment, wastewater treatment plants (WWTPs) in Chinese cities are putting increased pressure on energy consumption and exacerbating greenhouse gas (GHG) emissions. A carbon footprint is provided as a tool to quantify the life cycle GHG emissions and identify opportunities to reduce climate change impacts. This study examined three mainstream wastewater treatment technologies: Anaerobic–Anoxic–Oxic (A–A–O), Sequencing Batch Reactor (SBR) and Oxygen Ditch, considering four different sludge treatment alternatives for small-to-medium-sized WWTPs. Following the life cycle approach, process design data and emission factors were used by the model to calculate the carbon footprint. Results found that direct emissions of CO2 and N2O, and indirect emissions of electricity use, are significant contributors to the carbon footprint. Although sludge anaerobic digestion and biogas recovery could significantly contribute to emission reduction, it was less beneficial for Oxygen Ditch than the other two treatment technologies due to its low sludge production. The influence of choosing “high risk” or “low risk” N2O emission factors on the carbon footprint was also investigated in this study. Oxygen Ditch was assessed as “low risk” of N2O emissions while SBR was “high risk”. The carbon footprint of A–A–O with sludge anaerobic digestion and energy recovery was more resilient to changes of N2O emission factors and control of N2O emissions, though process design parameters (i.e., effluent total nitrogen (TN) concentration, mixed-liquor recycle (MLR) rates and solids retention time (SRT)) and operation conditions (i.e., nitrite concentration) are critical for reducing carbon footprint of SBR. Analyses of carbon footprints suggested that aerobic treatment of sludge not only favors the generation of large amounts of CO2, but also the emissions of N2O, so the rationale of reducing aerobic treatment and maximizing anaerobic treatment applies to both wastewater and sludge treatment for reducing the carbon footprint, i.e., the annamox process for wastewater nutrient removal and the anaerobic digestion for sludge treatment. View Full-Text
Keywords: carbon footprint; energy recovery; greenhouse gas emission; nitrous oxide; wastewater treatment; sludge treatment carbon footprint; energy recovery; greenhouse gas emission; nitrous oxide; wastewater treatment; sludge treatment
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Supplementary material

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Chai, C.; Zhang, D.; Yu, Y.; Feng, Y.; Wong, M.S. Carbon Footprint Analyses of Mainstream Wastewater Treatment Technologies under Different Sludge Treatment Scenarios in China. Water 2015, 7, 918-938.

Show more citation formats Show less citations formats

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Water EISSN 2073-4441 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top