ADVERTISEMENT

Postdenitrification Biofilters Can Be Optimized For Bioavailable Dissolved Organic Nitrogen Removal In Wastewater

The outlet water quality of many municipal wastewater treatment plants (MWWTPs) is characterized by high nitrogen strength, which can cause culture eutrophication. Due to the more and more stringent effluent total nitrogen discharge standards in China, MWWTPs need to upgrade and reconstruct. Postdenitrification biofilters (DNFs) have been used for tertiary nitrogen removal in MWWTPs because of their high efficiency and low cost. In this process, oxidized nitrogen is denitrified to nitrogen gas under anoxic conditions, with organic carbon as the electron donor.

Effluent nitrogen is composed of inorganic and organic nitrogen. Dissolved organic nitrogen (DON) can account for 52% and even up to 80% of the effluent nitrogen in low effluent total nitrogen MWWTPs. Effluent DON is the key factor to limit the total nitrogen concentration in the effluent of WWTPs. Moreover, it has been shown that a considerable fraction of effluent DON can be more bioavailable to bacteria and algae than inorganic nitrogen. Bioavailable DON (ABDON) is the component of DON which supports the growth of bacteria and algae. Unfortunately, most researchers and engineers working on DNFs have primarily focused on decreasing the inorganic nitrogen, whereas concern is rarely paid to the DON and ABDON.

ADVERTISEMENT
Image courtesy Haidong Hu

Recently, a team of researchers led by professor Hongqiang Ren from the State Key Laboratory of Pollution Control and Resource Reuse at Nanjing University evaluated the effect of the carbon-to-nitrogen (C/N) ratio (3, 4, 5, and 6) on the removal characteristics of DON and ABDON in the pilot-scale DNFs treating a real secondary effluent. The availability of an electron donor, conveniently expressed in terms of the C/N ratio, is the main control parameter for the DNF process. Optimizing external carbon addition not only improves the NDF process efficiency but also saves chemical costs and reduces secondary pollution (e.g., chemical oxygen demand). The chemical composition of DON in DNF effluent was also investigated with the purpose of facilitating a better understanding of the impact of the C/N ratio on DON bioavailability (ABDON/DON).

Results showed that DNFs effluent DON accounted for 31.2-39.8% of the effluent total nitrogen. The maximum effluent DON and ABDON concentrations both occurred in DNF operated at a C/N ratio of 3. Effluent DON from DNFs did not significantly differ when the C/N increased from 4 to 6; however, effluent ABDON and DON bioavailability significantly decreased with C/N ratios (p ňā 0.05, t-test). Effluent ABDON is an important issue and desirable to be removed by wastewater treatment plants because ABDON can be bioavailable to natural algae and support eutrophication in effluent receiving waters.

Overall, this study supports the benefit of a high C/N ratio during the DNF process in term of controlling the DON forms that readily stimulate algal growth. The results of this study provided a solution to control the eutrophication and would be helpful for the researchers and engineers working on the upgrading of municipal wastewater treatment plants. The work is currently published in the research journal Environmental Science & Technology.

These findings are described in the article entitled¬†Removal characteristics of dissolved organic nitrogen and its bioavailable portion in a postdenitrifying biofilter: effect of the C/N ratio, recently published in the journal¬†Environmental Science & Technology¬†(Environmental Science & Technology, 2018, 52, 757‚ąí764). This work was conducted by Haidong Hu, Kewei Liao, Jinju Geng, Ke Xu, Hui Huang, Jinfeng Wang, and Hongqiang Ren from¬†Nanjing University.

ADVERTISEMENT

Comments

READ THIS NEXT

An Invasive Plant Capable Of Causing Blindness And 3rd Degrees Burns Has Appeared In Virginia

A plant known as giant hogweed, sometimes just hogweed, may be spreading into the state of Virginia. Local plant experts […]

Pain Relief With Interference shRNA Proves Viable

Pain is the number one cause of distress, signaling the onset of tissue damage. In the vast majority of cases, […]

Occupational Interest And The Gender Divide

Published by Najib A. Mozahem College of Business Administration, Rafik Hariri University, Damour, Lebanon These findings are described in the […]

Is The Earth’s Sixth Mass Extinction Upon Us?

The phrase ‚Äėmass extinction‚Äô creates images of meteor strikes, exploding volcanoes and the rapid, brutal, destruction of the nonavian dinosaurs […]

Lead Iodide Nanosheets For Piezoelectric Energy Conversion And Strain Sensing

Harvesting ambient mechanical energy or sensing the mechanical signals based on nanomaterials for self-powered and flexible systems can provide potentially […]

Platelets Are Crucial Regulators Of Tumor Growth And Metastasis

Platelets are anucleate components of the blood, which are derived from megakaryocytes in the bone marrow. Platelets are necessary for […]

High Maternal Intake Of Gluten During Pregnancy Increases Risk Of Type-1 Diabetes In Offspring

A new study recently published in the BMJ provides evidence that high gluten consumption during pregnancy is associated with a […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?