Producing free nitrous acid – A green and renewable biocidal agent – From anaerobic digester liquor

Law, Yingyu; Ye, Liu; Wang, Qilin; Hu, Shihu; Pijuan, Maite; Yuan, Zhiguo

doi:10.1016/j.cej.2014.07.138

Cited by 101 publications

(60 citation statements)

References 34 publications

(39 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Free Nitrous Acid (FNA) has been demonstrated to be very effective in improving biomethane produced from digester liquor through complete conversion of ammonium to nitrite with alkalinity addition in a partial nitrification reactor (Law et al, 2015;Wang et al, 2014b). However when a source of nitrite is not available in wastewater treatment plants (WWTPs), this pre-treatment can become expensive due to the costs associated with the purchase of commercial nitrite and hydrochloric acid to achieve high FNA concentrations (Zahedi et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

Exploring alternatives to reduce economical costs associated with FNA pre-treatment of waste activated sludge

Zahedi¹,

Icaran

Yuan

et al. 2017

Bioresource Technology

View full text Add to dashboard Cite

Please cite this article as: Zahedi, S., Icaran, P., Yuan, Z., Pijuan, M., Exploring alternatives to reduce economical costs associated with FNA pre-treatment of waste activated sludge, Bioresource Technology (2017), doi: http:// dx.doi.org/10. 1016/j.biortech.2017.06.140 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractRecent studies have shown the effectiveness of Free Nitrous Acid (FNA) pre-treatment in enhancing sludge biodegradability and improving its methane production potential. FNA is regarded as an environmental friendly pre-treatment which can be easily applied when a source of nitrite is present in wastewater treatment plants. However, when nitrite is not available and needs to be purchased, this treatment can become less attractive due to the costs associated to nitrite. In order to overcome this possible limitation, two different strategies to optimize the use of nitrite during FNA treatment were investigated: i) Recovering NO2-after the pre-treatment is completed; and ii) Concentrating the sludge before FNA pre-treatment. Results show that recovering NO2-from the pre-treated sludge is not suitable due to the loss of soluble organic matter present in the supernatant after the pre-treatment. However, concentrating the sludge before the pre-treatment seems a good strategy to optimize the use of nitrite.

show abstract

Section: Introductionmentioning

confidence: 99%

Exploring alternatives to reduce economical costs associated with FNA pre-treatment of waste activated sludge

Zahedi¹,

Icaran

Yuan

et al. 2017

Bioresource Technology

View full text Add to dashboard Cite

show abstract

“…The first one took into consideration the fact that FNA can be produced on site. Previous study demonstrates that FNA can be produced in-situ as a by-product of wastewater treatment on site in a WWTP using anaerobic digestion liquor (Law et al, 2015). The ammonium (~ 1 g N/L) in the anaerobic digestion liquor can be converted into nitrite through partial nitritation resulting in a nitrite concentration of up to 1 g N/L at pH ~6, equivalent to an FNA concentration in the order of ppm level.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, it has been demonstrated that both FNA and H 2 O 2 can be produced as by-products of wastewater treatment through partial nitritation of anaerobic digestion liquor, with low chemical and energy input , Law et al, 2015, and through a bio-electrochemical system (Rozendal et al, 2009), respectively. In order to assess the potential economic feasibility of the proposed combined pre-treatment at full-scale, a desktop scaled-up study on a full-scale WWTP with a population equivalent (PE) of 400,000 and an anaerobic sludge digester with a hydraulic retention time (HRT) of 20 days was performed (Table 10).…”

Section: Combination Of Fna and Oxidants As A Potential Pre-treatmentmentioning

confidence: 99%

“…FNA, a renewable and low cost chemical that can be produced on site by nitritation of the anaerobic digestion liquor (Law et al, 2015), has been demonstrated to be a strong biocidal agent and effective in enhancing WAS biodegradability and methane production as discussed in section 1.3.3.4 (Pijuan et al, 2012, Wang and Yuan, 2015.…”

Section: Introductionmentioning

confidence: 99%

“…Though, biological nitritation could efficiently convert ammonium into nitrite (Law et al, 2015), acids are still required to achieve the pH that yields FNA at a desirable concentration for the sludge pre-treatment. With the assistance of electrochemical system, acids can be produced in the anode and the nitrite in the partially nitrated digested liquor can be concentrated into anode chamber as well, in which FNA can be formed.…”

mentioning

confidence: 99%

See 2 more Smart Citations

FNA-based pre-treatment of primary, secondary and digested sludge

Zhang¹

View full text Add to dashboard Cite

Wastewater treatment plants (WWTP) are widely applied in practice to remove nutrients from wastewater and to minimize its impact when discharged to the environment. However, approximately 1/3 of the total organic carbon is converted into waste activated sludge (WAS), the treatment and disposal of which accounts for up to 20~60% of the overall costs of the wastewater treatment due to its poor biodegradability. In order to achieve sludge reduction and maximize the methane production from WAS, pre-treatment is often required. The overall objective of this thesis is to investigate the effects of free nitrous acid (FNA, i.e. HNO2) pre-treatment on the biodegradability of primary, secondary and digested sludges in WWTPs and also to reveal the mechanisms by which FNA works to improve the sludge degradability.The feasibility of a novel pre-treatment strategy using combined FNA and hydrogen peroxide (H2O2) to enhance methane production from WAS was investigated. WAS from a full-scale plant was treated with FNA alone (1.54 mg N/L), H2O2 alone (10~80 mg/g TS), and their combinations followed by biochemical methane potential (BMP) tests. Combined FNA and H2O2 pre-treatment substantially enhanced methane potential of WAS by 59~83%, compared to 13~23% and 56% with H2O2 pretreatment alone and FNA pre-treatment alone respectively. Model-based analysis indicated the increased methane potential was mainly associated with an increase of up to 163% in rapidly biodegradable fraction with combined pre-treatment. In some WWTPs, primary sludge (PS) and WAS are commonly mixed and digested simultaneously in the anaerobic digester. In order to reveal whether and how the PS and WAS should be jointly II treated by FNA in WWTPs, the effects and mechanisms of FNA pre-treatment on methane production from PS was studied. Full-scale derived PS was pre-treated with FNA at concentrations of 0~3.85 mg N/L followed by BMP tests. FNA treated PS was then centrifuged to separate the supernatant from the solid phase and BMP tests were performed on both fractions. The FNA pre-treatments resulted in methane potential reductions of 1~7%. The methane production from both supernatant and solid phases had also decreased. The molecular weight and chemical structure analysis of components of the soluble phase showed very limited release of readily biodegradable substances from PS with the FNA pre-treatment. As the FNA pre-treatment compromised the methane production from PS, this indicates that FNA-based sludge pre-treatment technology should be implemented solely on WAS to maximise the methane production from the two sludge streams.The ever increasing production of the two sludge streams occurring due to increased population will create challenges for handling, treatment and disposal of the sludge at current capacity, making it difficult to achieve the desirable sludge reduction efficiency in anaerobic digestion. Post anaerobic digestion of anaerobically digested sludge (ADS) has been applied to enhance sludge reduction, however, so far this has had on...

show abstract