Khadir, Ali

Ali Khadir is an environmental engineer working on emerging pollutants, dyes and pharmaceuticals in aquatic media, and biological wastewater...

Joined:

About Khadir, Ali

Ali Khadir is an environmental engineer working on emerging pollutants, dyes and pharmaceuticals in aquatic media, and biological wastewater treatment, He has published several articles and book chapters in reputed international publishers,

Khadir, Ali

Titles from this speaker

Application of Vacuum Extraction to Anaerobic Digestion for Process Intensification and Resource Recovery

Abstract

The IntensiCarbTM process utilizes the decoupling of SRT and HRT, like recuperative thickening, to increase process capacity while simultaneously reducing the influence of toxic metabolic by products through extraction (ex. ammonia-N) and recover additional methane. This paper summarizes 3 years of research evaluating the efficacy of the process utilizing a side-by-side comparison of conventional mesophilic digestion with varying intensification factors (2x, 3x, 4x, 5x) in bench-scale trials conducted at Western University in London, Ontario digesting blend of primary and secondary sludge collected from the Greenway Wastewater Treatment Plant. Figure 1 provides a process flow diagram of the IntensiCarbTM process simulated in these tests. Figure 2, plots change in volatile solids reduction (VSr) in relation to hydraulic and solids retention times of IntensiCarb to explore its impact on the rate and extent of digestion. Based on this data it can be seen that the primary mechanism of process enhancement is the rate of digestion, rather than extent, being able to operate a higher loading rate, low HRT, with out significant increase in overall destruction at extended SRT. While some instability was observed in the higher loading rates it was transient during transition periods. With the move toward resource recovery, the energy yield of the digestion process is as critical as maximizing methane production per unit volume has potential long-term operating cost benefits as well as sustainability impacts. Figure 3, plots the impact of digester hydraulic retention time on the methane yield of the digester (m3-CH4/m3digester/d). Figure 3, clearly illustrates that with the IntensiCarbTM process the methane yield on an equivalent digester volume basis is more than 4.5 times higher than the conventional digester at 20 days SRT; 1.28 m3-CH4/m3digester/d verses 0.28 m3-CH4/m3digester/d, respectively. Furthermore, conventional mesophilic digestion typically does not operate, at scale, under 15 days of retention time. This is because below this level significant risk to process stability has been historically observed. The accumulation of ammonia has a self-limiting effect on anaerobic digestion. To date, no technology has effectively managed ammonia-N in-situ, resulting in risks for process instability and or significant population shifts, as reported by Mah et al. (2017) for THP. This is significant in that the control of ammonia in the digester could support high loadings without the negative impacts of toxicity and reduce return stream impacts, often a concern with high rate anaerobic digestion processes. The data shows (Figure 4) that as the digester load increased with IntensiCarbTM, the overall total ammonia-N levels remained around 800 mg-N/L or less, while a more conventional system would be expected to be operating at 2,100 to >5,000 mg-N/L. This observation alleviates one of the primary limits to anaerobic digestion. High loadings and high ammonia concentrations have been attributed to shifts in digester populations, as outlined by Mah et al (2017) when evaluating thermal hydrolysis. With similarly high loads but significantly reduced ammonia-N levels, the population profile of several of the test digesters were evaluated and compared to the control. The relative abundance of bacteria and archaea (methanogens) depicted in Figure 6 indicates that the relative abundance of archaea increases with intensification factor, approximately 40% (Figure 5). Looking at the specific methanogenic population present, there is a shift that occurs between the conventional (Control) digester relative to the intensified digesters. As the intensification level increases the methanogenic population shifts from one dominated by the low-growth rate Methanosaeta to one dominated by high-growth rate Methanosarcina (Figure 6). Some have suggested that digesters dominated by Methanosarcina have a higher overall capacity and stability due to their significantly higher maximum specific growth rate. The opposite was reported for thermal hydrolysis based digestion (Mah et al (2017)). Vacuum enhanced anaerobic digestion represents a novel process for the intensification of anaerobic sludge stabilization. Potentially offering unique opportunities for resource recover, ammonia-N and dissolved methane, as well as providing a mechanism to alleviate the current limitations associated with anaerobic digestion, metabolic byproduct toxicity.

The IntensiCarbTM, process is a vacuum enhanced anaerobic digestion process, that separates solids and hydraulic residence time. Resulting in increased process capacity by six times and in-situ removal of ammonia from the digestion process, exceeding the capacity of all commercially available sludge digestion processes on the market today. The process appears to select for increased methanogenic robustness and ammonia tolerance as well as create new opportunities for resource recovery.

SpeakerMuller, Christopher

Presentation time

16:00:00

16:20:00

Session time

15:30:00

17:00:00

SessionAdvances in Anaerobic Digestion

Session number219

Session locationRoom 344

TopicBiosolids and Residuals, Intermediate Level, Research and Innovation

Author(s)

Muller, Christopher, Khadir, Ali, Abdelrahman, Amr, Al-Omari, Ahmed, Jang, Eunkyung, Bell, Katherine, Norton, John, Sheculski, Chris, Santoro, Domenico, Nakhla, George

Author(s)C. Muller1, A. Khadir3, A. Abdelrahman3, A.A. Al-Omari1, E. Jang2, K. Bell1, J. Norton4, C. Sheculski2, D. Santoro2, G.F. Nakhla3

Author affiliation(s)1Brown and Caldwell, 2USP Technologies, 3Western University, 4Great Lakes Water Authority

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159715

Volume / Issue

Content sourceWEFTEC

Word count14

Description: Intensifying Anaerobic Digestion with a Side-Stream Vacuum-Based Biosolids Treatment...

Intensifying Anaerobic Digestion with a Side-Stream Vacuum-Based Biosolids Treatment Technology: Process Validation Exceeding Expectations

Abstract

This study evaluates the application of a novel ex-situ vacuum-enhanced anaerobic digestion technology, referred to as IntensiCarbTM (IC), for process intensification through decoupling SRT from HRT, and ammonia recovery. Findings revealed that the IC sustain almost the same methane yield and COD destruction efficiency as the control at three times the organic loading rate (OLR). Furthermore, the ammonia concentration in IC- digester operating at 3 times higher organic loading was pretty much the same as the control, demonstrating the effectiveness of IC-technology in elutriating a large fraction of ammonia from IC-digester into the condensate. This leads to stable digester operation as well as a potential to generate revenue. The combination of high organic loading and low ammonia concentrations resulted in the prevalence of the higher growth rate Methanosarcinaceae in the IC-digester compared to the low growth rate Methanoseata predominance in the control.

A novel ex-situ vacuum-enhanced anaerobic digestion technology was evaluated for process intensification in anaerobic digesters. This technology, referred to as IntensiCarbTM (IC), could increase the OLR and volumetric loading by 3 times while maintaining stable methane yields and COD destruction. Ammonia recovery, reduced digester size, as well as reduced nitrogen loadings in sidestreams, are the major advantage of IC-technology.

SpeakerKhadir, Ali

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionAdvances in Anaerobic Digestion and Sidestream Treatment

Session locationRoom S404a - Level 4

TopicIntermediate Level

Author(s)

Khadir, Ali

Author(s)A. Khadir 1; F. Omoye 2 ; E. Jang 3; D. Santoro 4; J. Walton 4; C. Muller 5; A. Al-Omari 6; K. Bell 7; G. Nakhla 8;

Author affiliation(s)Western University, Canada 1; Western University, Canada 2 ; USP Technologies, Canada 3; USP Technologies, Canada 4; USP Technologies, Canada 4; Brown and Caldwell, USA 5; Brown and Caldwell, USA 6; Brown and Caldwell 7; Western University, Canada 8;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825158983

Volume / Issue

Content sourceWEFTEC

Word count15

Base text size -

Khadir, Ali

About Khadir, Ali

My Recent Activity