The Ozmotics Insider

The rapid global increase of the population as well as the industrialization of the global economy have put the human population in direct or indirect exposure with waste water.

The exposure to waste water and microbiological organisms found within it is one of the biggest concerns in third world countries. Interestingly, the issue of accidental exposure and contamination of  drinking water with microbiological organisms commonly found in waste water, has not eluded even developed countries.

The commonly found organisms in domestic wastewater include enteric bacteria, viruses, and protozoan cysts. Most of these organisms had been closely linked to the outbreak of illnesses that range in severity from minor to most serious or even deadly.

The following is a short-list of bacteria and the associated illnesses each is responsible for:

Bacteria

• - Escherichia coli (enterotoxigenic) – Causes Gastroenteritis
• - Leptospira (spp.) – Causes Leptospirosis
• - Salmonella typhi – Causes Typhoid fever
• - Salmonella (≈2,100 serotypes) – Causes Salmonellosis
• - Shigella (4 spp.) – Causes Shigellosis (bacillary dysentery).
• - Vibrio cholerae -  Causes Cholera

Protozoa

• - Balantidium coli  – Causes Balantidiasis
• - Cryptosporidium parvum – Causes Cryptosporidiosis
• - Entamoeba histolytica – Causes Amebiasis (amoebic dysentery)
• - Giardia lamblia – Causes Giardiasis

Helminths

• - Ascaris lumbricoides – Causes Ascariasis
• - T. solium -  Causes Taeniasis
• - Trichuris trichiura – Causes Trichuriasis

Viruses

Enteroviruses (72 types, e.g.,  polio, echo, and coxsackie virus) – Cause Gastroenteritis, heart anomalies, meningitis.

• - Hepatitis A virus – Cause Infectious hepatitis
• - Norwalk agent  – Cause Gastroenteritis
• - Rotavirus – Cause Gastroenteritis

> Source: National Small Flow Clearinghouse: http://www.nesc.wvu.edu

Waste Water Treatment:

Historically, three distinct technologies have been used to treat waste water and destroy the microbiological contaminants within it.

1. UV Radiation - UV radiation is generated using an electrical discharge through a mercury vapor medium. The resulting UV radiation is used to incapacitate and destroy the microbiological growth inside the waste water.
2. Chlorination – Perhaps the most widely-used method for disinfecting waste water. Chlorine is a strong oxidant that destroys microbiological growth by oxidizing cellular material.
3. Ozonation – Ozone is also known as a strong oxidizing agent. In fact, the oxidation potential of ozone is much higher than the oxidation potential of chlorine (2.07 versus chlorine oxidation potential of 1.36).

Ozone versus Chlorine (Pros and Cons):

Perhaps the largest advantage of chlorine is the initial cost of the system. Chlorine is typically produced off-site and brought on-site for the treatment. As such the initial costs are typically lower.

Ozone treatment may on the other hand require a larger initial capital investment since ozone is typically produced on-site (due to the short life of the ozone, which is highly reactive) will quickly revert to more stable oxygen molecule.

However, once the technology is procured and installed the only additional cost of operating it is the cost of electricity and scheduled maintenance costs of the equipment therefore making the ozone less costly to use in the long-term.

Unlike chlorine, ozone leaves no residual trace elements once the treatment has been completed (any unused ozone will simply revert back to the more stable oxygen molecule). As such ozone is preferred where the water will be discharged back into the environment as it produces no trace residual pollutants.  The main downside of ozone, however is that it must be constantly introduced into the water being treated (even after the treatment) to prevent the recontamination of the water. Chlorine on the other hand can be dissolved and remain in the treated water therefore no follow-up treatment is needed.

The Method of Ozone Disinfection:

It is widely believed that ozone kills viruses, bacteria and other microbiological organisms by attacking the inner membrane wall of the microbiological organism’s cellular structure.

The effectiveness of ozone to destroy bacteria viruses and other microbiological organisms had been tested and results published in several scientific papers and other journals. The following is a summary of results published to date:

• - E. coli – Destroyed with 0.02 mg.min/l of O3 at pH: 6 to 7
• - Poliovirus 1 – Destroyed with 0.1-0.2 mg.min/l of O3 at pH: 6 to 7
• - Rotavirus  – Destroyed with 0.006-0.06 mg.min/l of O3 at pH: 6 to 7
• - Giardia lamblia cysts  – Destroyed 0.5-0.6 mg.min/l of O3 at pH: 6 to 7
• - Giardia muris cysts – - Destroyed 1.8-2.0 mg.min/l of O3 at pH: 6 to 7

The same experiment repeated at the same pH level using the chlorine as a disinfection agent:

• - E. coli – Destroyed with 0.034-0.05 mg.min/l of Cl at pH: 6 to 7
• - Poliovirus 1 – Destroyed with 1.1-2.5 mg.min/l of Cl at pH: 6 to 7
• - Rotavirus  – Destroyed with 0.01-0.05 mg.min/l of Cl at pH: 6 to 7
• - Giardia lamblia cysts  – Destroyed 47->150 mg.min/l of Cl at pH: 6 to 7
• - Giardia muris cysts  – Destroyed 30-630 mg.min/l of Cl at pH: 6 to 7

Note – For the destruction of the Giardia muris cysts, chlorine dioxide (ClO2) is reported as more effective although for all other biological organisms reported above, the concentration of chlorine dioxide was at par or significantly higher compared to simple chlorine molecule.

• - Giardia muris cysts  – Destroyed 7.2-18.5 mg.min/l of ClO2 at pH: 6 to 7

> Source: Ozonia Ltd – Switzerland

Using Ozone for Waste Water Treatment (Conclusion):

With the exception of the initial cost to deploy the technology, ozone has proven to be more effective, more environmentally friendly and has longer-term economical benefits to use in the waste water treatment process.  Unlike chlorine, ozone is effective in destroying a wide spectrum of microbiological organisms including some protozoa (Giardia lamblia and giardia muris cysts) which have been shown to be extremely resistant to chlorine.

If you have an application that requires waste water disinfection or treatment and need help sizing a unit please contact your Ozmotics representative at 1-877-386-3763.