Biodegradation Of persistent organic pollutants

Effluents generating from different industrial activities contain persistent, difficult to biodegrade pollutants in it. These pollutants have complex molecular structure and varying degree of biodegradability. The wastewater matrix is also of challenging nature due to presence of high salinity, toxic inhibitory substances which reduces biological activities of micro organisms a lot resulting in lower reduction efficiencies.

Biodegradation of persistent organic pollutants under such inhibitory and suboptimal conditions poses a principal issues as complex molecules require typically a consortia of micro organisms having different roles and tasks to perform for the biodegradation of the target molecule. Often these organisms have non flocculating nature and thus their retention in the reactor is a challenging task due to frequent wash out because of poor settling. This wash out results in very low removal efficiencies, lower process stability and thus lower reactor loading for suspended growth systems resulting in very large reactor volumes associated with bulking and other problems.

Levapor Carriers: An Ideal Habitat For Non Flocculating Organisms

Due to very high adsorption capacity of Levapor carriers resulting in very high surface area, the non flocculating microorganisms responsible for the degradation of complex molecules can be immobilized on Levapor carrier surface and thus can be retained within the biological reactor. The inner porosity of Levapor carriers also facilitate growth of microorganism within the inner pores which protect them against toxic shock loads and thus their complete wash out and inhibition can be prevented.

Reversible Adsorption: A Unique Feature Of Levapor Carriers

Due to impregnation of PU foam matrix with activated carbon, Levapor carriers provides a unique advantage of Powdered Activated Carbon Technology (PACT) in combination with attached growth process.

When a toxic organic substance enters Levapor based reactor, it initially gets adsorbed on the carrier material due to activated carbon. This adsorption reduces the bulk liquid concentration of the toxic substance significantly which reduces its toxic effect on the suspended growth microorganisms.

Moreover, the carrier material also allows higher growth of microorganisms responsible for the biodegradation of the attached pollutant. Thus, the attached pollutants are effectively and efficiently biodegraded by the microorganisms reducing the concentration of adsorbed pollutant. This degradation of pollutants regenerates the activated carbon restoring the adsorption capacity of the carrier material termed as “reversible adsorption and regeneration’’ . It is unique feature of Levapor carriers offering remarkable process stability against toxic shock loads and effective biodegradation of toxic substances present in the industrial effluents.

As shown in the above figure, when high amount of 2 Chloro Aniline (2CA) is added to Levapor reactor, within few minutes of addition, its concentration in the liquid phase is reduced a lot confirming adsorption on the carrier and reducing its toxicity in the liquid phase. Over next few hours, the biodegradation of 2CA is initiated which is confirmed by the release of Chloride ion in the liquid phase.

Advantages of Levapor Carriers

  • Efficient biodegradation of persistent pollutant
  • Higher COD reduction efficiencies
  • Higher volumetric loading resulting in smaller reactor volumes
  • Remarkable process stability against toxic shock loads and wide range of reactor conditions

We provide complete process engineering from concept to commissioning of the process for your complex effluent treatment requirement. Connect with Levapor team for developing optimal process for your complex effluent treatment.

Large voids tend to cause detachment of biofilms due to high shear forces and thus would increase the biofilm formation time during the initial colonization. During the event of toxic shock loads, a larger fraction of the biofilm is exposed to the toxicity which may cause performance deterioration.

Smaller and deeper voids allow for rapid formation of biofilms within the deeper pores due to lower sloughing during start up process. Fine pore structure with deeper voids also protects bacteria against toxic shock loads.  So MBBR media with fine pore structure provide much better protection against shock loads and quicker start up compared to the element having large and exposed voids.  

Finer voids also allow for growth of thinner biofilms which keeps a large fraction of biomass present in the biofilm exposed to the bulk liquid of the reactor for substrate uptake. This provide better diffusion gradients allowing better reduction efficiencies.   

Finer and deeper cavities allow for growth of specific type of microorganisms such as Anammox bacteria and Denitrifying bacteria within the inner pores increasing the process efficiency and reliability over the period of operation. However, too fine pore structure may tend to clog the carrier material with excessive biofilm formation within the inner pore and make it heavier. Further due to poor accessibility of the inner pore for substrate, the inner biofilms become less active and redundant over period of operation.

Thus, a MBBR media material having adequate fine pore structure and inner porosity is very much desirable as it provides numerous benefits such as:

  • Faster and better colonization
  • Protection of bacteria against shock loads at the same time provides adequate accessibility to inner biofilms for better substrate diffusion.
  • Adequate detachment, shearing and erosion of biofilms on continuous basis to prevent excessive growth and clogging.
  • Thinner biofilm growth with better diffusion gradients allowing better substrate uptake and reduction efficiencies.

On the contrary present plastic material based MBBR media element have larger voids which has many disadvantages such as:

  • Poor initial colonization due to shearing of biomass during start up.
  • Minimal protection against toxic shock loads before thick biofilms are formed with EPS to protect them.

Poor diffusion gradient with less accessibility to inner biofilms under thick biofilm formation.

Author Bio

Amit Christian is a MSc graduate in Environment Science from Middlesex University, London, UK. He has been active in the field of water and wastewater treatment since 1998. He specializes in design, engineering, and management of various biological wastewater treatments such as Activated Sludge Process (ASP), Sequencing Batch Reactor (SBR), Moving Bed Bio Reactor (MBBR), Integrated Fixed Film Activated Sludge (IFAS). He has helped various Industrial and Municipal clients in troubleshooting , optimizing their biological wastewater treatment processes to achieve latest Stringent norms for Ammonia Removal.