///How it works
How it works 2017-09-19T19:15:21+00:00

How it works

OMA App provides a rapid field indicator of effluent quality to assist Council in the management of onsite facilities by providing a guide of the presence of suspended solids (Turbidity/TSS – Total Suspended Organic Solids).*

The Science

OMA App does not replace the need for laboratory testing for those facilities Council may consider high risk.

The most accurate method of measuring suspended solids is a laboratory process that is expensive, time-sensitive, time-consuming (transporting samples to the laboratory) and impractical for application in the field. A long-established and accepted alternative utilises a Secchi disk and visual interpretation by the person conducting the test.**

OMA draws on the principals of the conventional Secchi tube, which needs to be filled to a depth of 1 metre, for the OMA sample tube that requires only 100mm.

The Basic Process

  • A small sample of effluent is placed in the OMA tube to the level indicator on the side of the tube.

  • A cap is placed on the top of the tube with a focal distance of 150mm to the Secchi disk. This allows a smart device camera to focus on the Secchi disk in the base of the tube through a consistent depth sample.

  • The OMA app instantly analyses a photo of the Secchi disk and calculates a grey-scale percentage relative to a baseline photo of the empty tube.

  • This value is correlated against a known TSS sample of effluent prepared by a NATA laboratory with accurate mg/litre of TSS to the values of 5, 10, 15, 20, 25, 30, 35 and 40.***

Note: Results can be impacted by operation and field conditions.

* The presence of suspended solids is also an important marker of biochemical oxygen demand (BOD5). The test for BOD5 is a bioassay procedure that measures the oxygen consumed by bacteria from the decomposition of organic matter over 5 days.

The existence of organic matter facilitates the presence of bacteria that can be a source of transmission of harmful organisms that pose a risk to human and environmental health.

NOTE: The presence of high TSS/organic matter can result in masking during the sterilization process by both Chlorine and Ultra Violet Light by shielding bacteria from the sterilization method. A high TSS indicator would warrant the need to ensure effective dosing, retention time for chlorine and condition, operation of the UV lamp, especially where the disposal method used is above-ground irrigation.

 ** The Secchi disk was created in 1865 by Angelo Secchi, and evolved into a black and white disk in the bottom of a Secchi tube. The Secchi tube is filled with sample water to a depth of 1 meter, with the sample water released slowly from the bottom until the Secchi disk is visible with the naked eye looking down through the water sample. The measurement of the depth of water is then used to calculate a turbidity/ TSS percentage in the water by correlation with laboratory data.

*** Multiple sample runs were analysed by the OMA app to develop a percentage of TSS mg/l to grey-scale value for each of the TSS loading rates to provide a much more reliable field value. By correlating the new sample grey-scale value against the TSS grey-scale values derived from the laboratory samples, OMA returns an indicator result of estimated TSS in the field sample.

Disclaimer: The OMA app does not and is not intended to replace the requirement for laboratory testing to provide an accurate TSS and BOD5. It is to provide a more reliable and consistent indicator of TSS when compared to a visual interpretation by the licenced technician servicing the facility.