A novel method for valuable resource recovery from biosolids (waste activated sludge) and it's safe return into circular economy as a fertilizer substitude

OZOLIZ is a proprietary and patented method for accelerating the conventional aerobic digestion (lysis) of biosolids and providing total disinfection of pathogens along with the substantial removal of man-made anthropogenic compounds and contaminants of emerging concern (CECs).


Approximately 2/3 of existing water pollution control plants (WPCPs) employ aerobic digestion for sludge treatment. Until replacing all of these small plants with contemporary anaerobic digestion, there is an essential need for disinfecting aerobically digested sludges to minimize
re-contamination risks after disposal.



The patented method intermittently applies ozone gas (O3) to biosolids, to destruct only a small portion of micro-organisms (in the biosolids) to make them "readily digestible food" for the remainder micro-organisms by promoting aerobic digestion; continuously repeating: "partial microbial destruction with ozone" and then "aerobically digesting the food", achieving superior disinfection of biosolids accumulated in wastewater treatment plants, generating a fully-stabilized product as a fertilizer sustitude with a commercial value.



  • Kills pathogens to at least 6-log removal (99.9999%) providing active disinfection of biosolids
  • Produces a fully-stabilized earth-like final product, achieving "USEPA Class A" biosolids standard with a commercial value as a fertilizer-aid
  • Destructs up to 95% man-made complex compounds like EDCs and PAHs and eliminating concerns for contamination of drinking water resources
  • Reduces the final biosolids volume by up to 70% (in comparison to  40% removal with conventional aerobic digestion)
  • Achieve the above results in 3 to 5 days hydraulic retention time (in comparison to 15 to30 days with conventional aerobic digestion)
  • Achieve the above results while utilizing approx. 25% less energy than the conventional aerobic digestion

Advance on State of the Art 

As the novel method for "sequentially intermittent ozone-assisted aerobic biosolids digestion" is new and surpasses the benefits of previously "tried" ozone methods for sludge destruction. Application of ozone in biological treatment has been well documented to date, therefore introduction of ozone into a main stream biological treatment tank is not unique on its own as claimed by [R1]. However, sequentially intermittent ozone application, OZOLIZ process, in a dedicated tank, “aerobic digester”, is a unique and has not been reported as yet. OZOLIZ is specifically implemented in the excess sludge (biosolids) digestion reactor which is segregated from the mainstream aeration reactor.


In contrast to OZOLIZ, LIBING CHU et al. [R2] mentions in the literature that: “The ideal solution to the problem of sludge disposal is to combine sludge reduction with the removal of pollution at the source (i.e. at mainstream aeration reactor which is NOT at a segregated aerobic sludge digester”. Using ozone in the mainstream process trainm as claimed by [R1], are "old" methods that have NOT been widely adopted due to shortcomings in design and operation. These shortcomings are overcome by OZOLIZ using newly developed know-how and associated intellectual property backed by multiple patents complimentary to each other.



[R1] Fei-yun Sun, Xiao-mao Wang, Xiao-yan Li, Effect of biopolymer clusters on the fouling property of sludge from a membrane bioreactor (MBR) and its control by ozonation. Process Biochemistry, Volume 46, Issue 1, January 2011


[R2] LIBING CHU et al.: "Progress and perspectives of sludge ozonation is a powerful pretreatment method for minimization of excess sludge production" WATER RESEARCH, 2009-02-20, vol. 43, no. 7.


Biological wastewater treatment generates organic residuals called “biosolids”, which contain essential nutrients that, when properly treated, can be applied as fertilizer to farmland. However, only 37% of treated biosolids currently go to farmlands in the EU, due to insufficient or no treatment at all. We’d like to properly treat and convert this wasted resource into a sanitized, nutrient-rich, bio-fertilizer product that replaces synthetic chemical fertilizers.

Another reason is incidents like the following:  Antidepressants found in fish brains in Great Lakes region: http://aware-simcoe.ca/2017/08/antidepressants-found-in-fish-brains-in-great-lakes-region/

There are municipalities who have already adopted premium biosolids treatment processes and achieving high quality biosolids; however, numbers are limited to only a handful. For example: DC Water (Washington, DC, USA) has a biofertilizer product (anaerobically treated) which is sold to the public at approx. 7.5 $US/cubic yard (~10 $US/m3) and they are planning to bag and sell the product in small quantities.

Ref: Chris Peot, Director of Resources Recovery, September 2017

Full-Scale Pilot Demonstration

To demonstrate, in full scale, the feasibility and performance of the patented ozone-assisted aerobic-digestion process at University laboratory. The full-scale operating data will validate the bench-scale performance results. Successful scale-up will provide conclusive proof to potential customers that the technology will create a sanitized, nutrient-rich, bio-fertilizer product with a competitive commercial value to replace synthetic chemical fertilizers.

Returning biosolids to farmland completes a natural food-cycle: farm’s produce is consumed by humans who then produce waste, which, when treated appropriately, is returned back to the farms to offset input costs and deliver remarkable yield results. In this way, nutrients such as nitrogen and phosphorus are returned farms for use in crop production, sod farming, soil remediation, horticulture, and more. 

Side-by-side Technology Comparison

Need for Biosolids Disinfection Regulations

As a passionate advocate for biological biosolids sanitation and safe recovery of biosolids, MixAnox believes that there is an urgent need for new biosolids sanitation guidelines. While disinfection of treated wastewater effluent is strictly legislated, why not legistate disinfection of biosolids before disposal or land application?


For biosolids sanitation, it is about time to move on from Biosolids Pathogen and Vector Attraction Reduction Guidelines from two decades ago to a "New Biosolids Disinfection and Safe Reuse Guideline". New and emerging technologies are available for both enhancing conventional aerobic-digestion and anaerobic-digestion. However, any new technology comes with a cost and no one seems to be adapting these technologies volunterily. Regulators must review available technologies and accordingly update the existing guidelines and legislations. 

Man-made anthropogenic compounds and contaminants of emerging concern (CECs) aside, pathogen accumulation and subsequent re-activation in sewage sludge storage after conventional aerobic digestion seems to be a big problem. The following article may also help increase public awareness for the pathogens and other unwanted subsances accumulating in biosolids. Interest in this topic will only grow and spark further research and perhaps push the envelope for a new Biosolids Disinfection Legislation.


The following Linkedin article talks further about why existing conventional aerobic digestion systems should be improved: 

Post COVID-19 Biosolids: Discard or Recover How?


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