THE ENVIRONMENTAL IMPACT OF VIRKON S

Introduction

As part of Antec's commitment to supporting its customers, we are delighted to provide an overview of the environmental issues relating to the use of our disinfectants. There can be no doubt that this is an increasingly important issue to all our customers, and such a document is vital for informed decision making.

Following the results of independent analysis performed by the Water Research Council, Marlow, Buckinghamshire, UK a report on Virkon S is presented. To the best of our knowledge no other manufacturer has submitted its products to such rigorous independent analysis.

The independent data uses international protocols and should be acceptable to regulatory bodies such as the Environment Agency.

A comparison is made with peracetic acid as this type of disinfectant is considered to be environmentally friendly. In all three tests performed by the WRC, Virkon S proved to be even less ecotoxic than peracetic acid.

The other aspect of a product's environmental impact is its biodegradation. Data to show the independently assessed biodegradation is presented at the end of the report.
 

A. Eco-toxicity
 

1. Effect on the performance of Sewage Treatment Facilities
 

Summary

Antec Virkon S was the least toxic to anaerobic sludge and should not pose a threat to Sewage Treatment Facilities. This confirmed earlier independent work performed by Anglian Water.

Materials and Methods

This was performed using standard OECD protocols. Assessment of the toxicity of the disinfectants to the anaerobic gas production from sewage sludge was carried out as detailed in the Methods for the Examination of Waters and Associated Materials 1986 (HMSO 1987). Primary digesting sludge (obtained from Wargrave, Sewage treatment works, Henley, Oxon) was incubated alone (control) and simultaneously with a range of concentrations of test material in sealed bottles for 3 days at 35^OC. The increase in headspace volume resulting from the production of carbon dioxide and methane was measured, and the amount of gas calculated by means of a calibration graph. The inhibition of gas production by the test material was calculated from the volumes produced in the test and control bottles and is expressed as percentage inhibition, calculated as follows:

Each disinfectant was applied to digested sludge to give the following concentrations: 0.2, 0.5, 1.0, 2.5 and 5.0 g/l. Each test was carried out in triplicate. The EC₅₀ value was calculated from a plot of percentage inhibition against the log concentration of the test chemical.

Results

Antec Virkon S demonstrated an EC₅₀ of 920 (+/- 19) mg l^-1 , which is 20% better than the value of 770 (+/- 28) mg l^-1 for peracetic acid.

Interpretation

This is the equivalent of 1 litre of 1% Virkon S solution in just 10.87 litres of water. At this level would not be a major problem for sewage system. However, as an extreme the European Union states that an environmentally safe, or 'predicted no effects concentration', is 1% of the EC₅₀ value. Thus, the theoretical predicted no effects level for 1 litre of 1% Virkon S solution would be 1087 litres, as against 1299 litres for peracetic acid.

This finding is entirely consistent with findings by Anglian Water. In a 5 day Biochemical Oxygen Demand test a 1% solution of Virkon S subsequently diluted to a level typically found in effluent streams did not inhibit the BOD test. From this it can be concluded that Virkon S was degradable under the conditions of test and as such would not affect the functioning of sewage treatment plants. Anglian Water stated;

"In the dilution normally encountered all of the (Virkon S) ingredients are either decomposed and/or biodegraded and are comparatively harmless. The triple salt of potassium monopersulphate will decompose into harmless by-products. In the aqueous environment the product will eventually degrade and should pose no problems to sewage treatment processes."
 

2. Soil toxicity test using the earthworm, Eisenia foetida

Summary

Antec Virkon S shows low toxicity to earthworms and can be described as being 'non-toxic' according to EU guidelines.

Materials and Methods

Acute tests using Eisenia foetida were carried out according to OECD method 207 'Earthworm Acute Toxicity Tests' (OECD 1984b). In summary the protocol involves exposing earthworms to the test substance through contact with treated filter paper in order to determine the LC50 i.e. the interpolated concentration which would result in a mortality of 50% of an exposed population within the test period (48 hours). Test organisms were obtained from a commercial supplier, Original Organics.

In the definitive tests exposure concentrations for Antec Virkon S and peracetic acid were;

0, 3,6,12,24,48 mg cm^-2

Cleaned depurated worms of standard size and age were placed in sealed, ventilated glass tubes lined with filter paper to which 1 ml of test solution (made from deionised water) had been applied. Ten worms , each held individually, were exposed per treatment. They were held in the dark at 20 +/- 2⁰C for 48 hours after which the number of dead worms was used to calculate the LC₅₀, calculated by Probit analysis.

Results

Antec Virkon S demonstrated an LC₅₀ of 1872 mg kg^-1 , which is 53% better than the value of 1224 mg kg^-1 for peracetic acid.

Interpretation

Both Antec Virkon S and peracetic acid can be interpreted as being 'non-toxic' according to EU standards.

The LC₅₀ is equivalent to adding 1 kg of Antec Virkon S to just 5.34 kg of soil. However, as an extreme the European Union states that an environmentally safe, or 'predicted no effects concentration', is 1% of the lC₅₀ value. Thus, the theoretical predicted no effects level for 100l of 1% Virkon S solution would 534 kg of soil.
 

3. Freshwater toxicity using Daphnia magnia (water flea) as the test organism
 

Summary

The effect on aquatic life is likely to be an issue of concern. The Environment Agency (formerly National Rivers Authority) may expect data to be provided in respect of aquatic organisms for a disinfectant. The data below should be acceptable to the Environment Agency.

Materials and Methods

Acute tests using Daphnia magna were carried out according to OECD method 202 part I 'Daphnia sp. Acute Immobolisation Test' (OECD 1984a). In summary the protocol involves exposing waterfleas to the test substance in solution in order to determine an EC50 i.e. the interpolated concentration which would result in loss of mobility of 50% of an exposed population within the test period (48 hours).

The tests were carried out according to WRc's standard operating procedure (WRc 1991). Test organisms were obtained from WRc's long term culturing facility. In the definitive tests concentrations used were as follows;

0,1,2.2,4.6,6.0,10 mg ^-l

Juvenile (<24 hours old) Daphnia were used in each case, with exposure in groups of 5 and each test concentration duplicated (i.e. 10 individuals per exposure). All tests were conducted using clean groundwater at 22+/- 2⁰C to make up test dilutions. Numbers of immobile Daphnia i.e. those which were dead or 'functionally dead' were recorded after 2, 24 and 48 hours exposure, and the 48 hour EC₅₀ was calculated by Probit analysis.

Results

All water control quality values (pH, dissolved oxygen, temperature and hardness) were within acceptable test boundaries in the definitive Daphnia tests, and control immobilisation was 0% in every case.

Antec Virkon S demonstrated an EC₅₀ of 6.5 mg l^-1 , against 5.9 (95% Confidence Interval 5.3-6,5) mg l^-1 for peracetic acid.

Interpretation

Classification of products according to acute toxicity are designed to be relative rather than absolute. According to the EU Directive 67/548/EEC (Dangerous Substances Directive) Antec Virkon S is classified as toxic, though using the same system a standard Quaternary Ammonium compound, would be classified as very toxic. Indeed the latter has an EC₅₀ of less than 1 mg l^-1 making it at least more than 6.5 times more toxic.
 

B. Biodegradation
 

Virkon S consists mainly of inorganic salts which decompose into harmless by-products. The surfactant is a salt of straight chain alkyl benzene sulphonate complying with EU directive 82/243 giving more than 90% biodegradability under OECD test conditions.

For completeness of presentation the data from Anglian Water is presented again. In a 5 day Biochemical Oxygen Demand test a 1% solution of Virkon S subsequently diluted to a level typically found in effluent streams did not inhibit the BOD test. From this it can be concluded that Virkon S was degradable under the conditions of test and as such would not affect the functioning of sewage treatment plants. Anglian Water stated;

"In the dilution normally encountered all of the (Virkon S) ingredients are either decomposed and/or biodegraded and are comparatively harmless. The triple salt of potassium monopersulphate will decompose into harmless by-products. In the aqueous environment the product will eventually degrade and should pose no problems to sewage treatment processes."