Excessive greenhouse gas emissions from wastewater treatment plants by using the chemical oxygen demand standard

Abstract

Chemical oxygen demand (COD) is widely used as an organic pollution indicator in wastewater treatment plants. Large amounts of organic matter are removed during treatment processes to meet environmental standards, and consequently, substantial greenhouse gases (GHGs) such as methane (CH4) are released. However, the COD indicator covers a great amount of refractory organic matter that is not a pollutant and could be a potential carbon sink. Here, we collected and analysed COD data from 86 worldwide municipal wastewater treatment plants (WWTPs) and applied a model published by the Intergovernmental Panel on Climate Change to estimate the emission of CH4 due to recalcitrant organic compound processing in China’s municipal wastewater treatment systems Our results showed that the average contribution of refractory COD to total COD removal was 55% in 86 WWTPs. The amount of CH4 released from the treatment of recalcitrant organic matter in 2018 could have been as high as 38.22 million tons of carbon dioxide equivalent, which amounts to the annual carbon sequestered by China’s wetlands. This suggests that the use of COD as an indicator for organic pollution is undue and needs to be revised to reduce the emission of GHG. In fact, leaving nontoxic recalcitrant organic matter in the wastewater may create a significant carbon sink and will save energy during the treatment process, aiming at carbon neutrality in the wastewater treatment industry.

Simple Genomic Traits Predict Rates of Polysaccharide Biodegradation

“…14 indicator of organic pollution. 15,16 However, in modern polymer engineering, BOD measurement faces limitations in high-throughput industrial settings dealing with a diverse range of synthesized polymers. Methods to assess biodegradation that are scalable and applicable to a wide variety of substrates are crucial to meet the demands of rapid synthetic biopolymer production in the modern chemical industry.…”

“…Originating from wastewater treatment practices in the late 19th century, BOD measures the oxygen consumed by microorganisms breaking down organic matter in water . In environmental engineering, especially in bioreactors and wastewater treatment plants, BOD serves as a widely used indicator of organic pollution. , However, in modern polymer engineering, BOD measurement faces limitations in high-throughput industrial settings dealing with a diverse range of synthesized polymers. Methods to assess biodegradation that are scalable and applicable to a wide variety of substrates are crucial to meet the demands of rapid synthetic biopolymer production in the modern chemical industry.…”

Energy-Efficient AnMBRs Technology for Treatment of Wastewaters: A Review

“…Indeed, WWTPs provide the wastewaters treatment from chemical oxygen demand (COD), nitrogen (N) and phosphorous (P), as well as the production of an effluent free of pathogens [16]. Unfortunately, WWTPs contribute to the production and emission of CO 2 , CH 4 and N 2 O, resulting in the greenhouse effect [17][18][19][20][21], which was recognized as one of the major negative impacts on the environment. It was noted that each kWh of produced electricity leads to release of 0.9 kg CO 2 [22].…”

Cometabolic bacterial and fungal remediation as a promising strategy for recycled paper and cardboard mill wastewater treatment

“…These industries discharge reddish-brown colored wastewater containing hazardous pollutants such as chemical oxygen demand (COD) and color derived from lignin (Zwain and Dahlan, 2014;Abedinzadeh et al, 2018). COD represents the concentration of organic matter in wastewater, including biodegradable and nonbiodegradable organic compounds (Lv et al, 2022), leading to adverse effects on receiving aquatic environments, including photosynthesis restriction, pH change and dissolved oxygen (DO) content reduction (Patel et al, 2021). The color is also a challenge for treatment units and water reuse (Abedinzadeh et al, 2018).…”