Enhancing sludge biodegradability through free nitrous acid pre-treatment at low exposure time

Zahedi, S.; Icaran, Pilar; Yuan, Zhiguo; Pijuan, Maite

doi:10.1016/j.cej.2017.03.120

Cited by 37 publications

(19 citation statements)

References 28 publications

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“…Thus, the pretreatments disrupted cell walls and EPS in waste activated sludge due to their biocidal effect, which affects protein much more than polysaccharide. This agrees with previous studies, in which a similar trend is observed [12,33]. All three input variables, with p-value<0.05, had a significant effect on the model, while the effect of the input parameters on each other will be ignored due to p-value > 0.05.…”

Section: Discussionsupporting

confidence: 92%

Process optimization and effect of thermal, alkaline, H2O2 Oxidation and combination pre-treatment of sewage sludge on solubilisation and anaerobic digestion

Siami

Aminzadeh

Karimi

et al. 2020

Preprint

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Background This study investigated the feasibility of enhancing anaerobic digestion of sewage sludge with triple, dual, and individual pre-treatment of waste activated sludge with heat, alkalinity, and hydrogen peroxide. These pre-treatments disrupt sludge flocs, organisms’ cell walls, extracellular polymeric substance, and intracellular organic matter, which increase biodegradability and hydrolysis rate of organic matter. In addition, the influence of various variables on methane production was analyzed using the response surface methodology with the quadratic model. Eventually, an optimized temperature and chemical concentration for the highest methane production and lowest chemical usage is suggested.Results The highest amount of methane production was obtained from the sludge pretreated with triple pretreatment (heat (90°C), alkalinity (pH=12), and hydrogen peroxide (30 mg H2O2 /g TS)), which had better performance with 96% higher than that of the control sample with Temperature of 25°C approximately and alkalinity of pH=8. Response surface methodology with the quadratic model was also used for analyzing the influence of temperature, pH, and hydrogen peroxide concentration on anaerobic digestion efficiency. It was revealed that the optimized temperature, pH, and hydrogen peroxide concentration for maximizing methane production and solubilisation of organic matter and minimizing thermal energy and chemical additives of the pre-treatments are 83.2°C, pH=10.6 and 34.8 mg H2O2 /g TS, respectively, has the desirability of 0.67.Conclusion This study reveals that triple pre-treatment of waste activated sludge performs better than dual and individual pre-treatment, Respectively. The enhanced methane production can be used as an important renewable energy resource in wastewater treatment plants for producing electrical and thermal energy. Furthermore, exploiting a higher amount of methane in the anaerobic digestion stage decreases methane emission to the atmosphere in dewatering and landfilling stages and enhances the quality of digested sludge, bringing about environmentally friendly and economically attractive sewage sludge treatment process.

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Section: Discussionsupporting

confidence: 92%

Process optimization and effect of thermal, alkaline, H2O2 Oxidation and combination pre-treatment of sewage sludge on solubilisation and anaerobic digestion

Siami

Aminzadeh

Karimi

et al. 2020

Preprint

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“…The higher efficiency of combined pre-treatments in SCOD enhancement is attributable to the synergistic effect of radicals and oxidative chemicals released by FNA and Fenton reagent simultaneously. The SCOD enhancement from FNA pre-treatment, in this study, is in agreement with, but slightly higher than the research carried out by Zahedi et al [17] and Wang et al [26], which could be attributed to sludge specifications employed in this study.…”

Section: Degradation Of Organic Matterssupporting

confidence: 92%

“…It generates hydrogen peroxide (H2), peroxynitrite (ONOO-), nitrogen dioxide (˙NO2), hydroxide ion (˙OH -) and nitric oxide (˙NO) which have inhibitory impacts on key microorganisms in wastewater treatment plants at part per billion (ppb) levels [16]. Zahedi et al [17] demonstrated that after 5 hours of exposure time at 2.49 mg N-HN2/L, cells' viability in waste activated sludge declined by 80%, and methane production increased by 20%.…”

Section: Introductionmentioning

confidence: 99%

“…Considering that, this study aimed for assessing the synergistic effect of combined FNA and Fenton pre-treatments on 1) methane production from anaerobic digestion of waste activated sludge, 2) solubilisation of organic matter and 3) destruction of organic matter during the digestion. For FNA pre-treatment, two concentrations (1.5 and 2.5 mg HNO2/L) at 5 hours exposure time were considered [17] and for Fenton pre-treatment, two concentrations of H2 (25 and 50 g H2/kg TS) with a constant ratio of H2/Fe+2 (1/0.067) at 1 hour exposure time were employed [20,[23][24][25]. Combination of these conditions was also used for assessing the synergistic effects of FNA and Fenton.…”

Section: Introductionmentioning

confidence: 99%

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The synergy of combined free nitrous acid and Fenton technology in enhancing anaerobic digestion of real sewage waste activated sludge

Karimi

Hallaji

2019

Preprint

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Background Recently, free nitrous acid (FNA) pre-treatment of sewage waste activated sludge has been introduced as an economically attractive and environmentally friendly technique for enhancing methane production from the anaerobic digestion process. Fenton pre-treatment of sewage sludge, as an advanced oxidation process, has also been introduced as a powerful technique for methane improvement in a couple of studies. This study, for the first time, investigates the synergy of combined FNA and Fenton pre-treatment technologies in enhancing the methane production from the anaerobic digestion process and reducing waste sludge to be disposed of. Actual secondary waste activated sludge in laboratory-scale batch reactors was used to assess the synergistic effect of the pre-treatments. The mechanisms behind the methane enhancement were also put into perspective by measuring different microbial enzymes activity and solubilisation of organic matter. Result This study revealed that the combined pre-treatments release organic matter into the soluble phase significantly more than the bioreactors pre-treated with individual FNA and Fenton. For understanding the influence of pre-treatments on solubilisation of organic matter, soluble protein, soluble polysaccharide and soluble chemical oxygen demand (SCOD) were measured before and after the treatments and it was shown that they respectively increased by 973%, 33% and 353% after the treatments. Protease and cellulose activity, as the key constituents of the microbial community presenting in activated sludge, decreased considerably within the combined pre-treatments (42% and 32% respectively) and methane production enhanced by 43-69%. Furthermore, total solids and volatile solids destruction improved by 26% and 24% at the end of anaerobic digestion, which can reduce transport costs of sludge and improve the quality of sludge for application in farms and forests. Conclusions The results obtained from the experiments corroborate the synergic effect of the combined FNA and Fenton pre-treatment technologies in degrading the organic and microbial constituents in waste activated sludge, which improved methane production accordingly. This is of paramount importance because the total costs of wastewater treatment plants operation and greenhouse gas emission from sludge treatment and disposal processes would reduce considerably, which pave the way for the implementation of these technologies.

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“…These conditions have been demonstrated to significantly enhance methane production (Zahedi et al, 2017a(Zahedi et al, , 2017b(Zahedi et al, , 2016). …”

Section: Fna Pre-treatment and Bmp Testsmentioning

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

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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.

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Enhancing sludge biodegradability through free nitrous acid pre-treatment at low exposure time

Abstract: The effectiveness of low free nitrous acid (FNA) pre-treatment times (PTs) (<8 h) on waste activated sludge (WAS) is not known. This study explores the effectiveness of four different FNA concentrations (0, 2.49, 3.55 and 4.62

Cited by 37 publications

References 28 publications

Process optimization and effect of thermal, alkaline, H2O2 Oxidation and combination pre-treatment of sewage sludge on solubilisation and anaerobic digestion

Process optimization and effect of thermal, alkaline, H2O2 Oxidation and combination pre-treatment of sewage sludge on solubilisation and anaerobic digestion

The synergy of combined free nitrous acid and Fenton technology in enhancing anaerobic digestion of real sewage waste activated sludge

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

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