Sewage Effluent Testing
Sewage pollution from shipping has always been in the spotlight. Without comprehensive checks on Sewage Effluent, it can have catastrophic effects on the environment and the wellbeing of both human and aquatic life. To combat this, Sewage Effluent regulations have been in effect for over a hundred years and they will continue to get more and more stringent in the future as public awareness grows.
However, some of the terminology and procedures involved with sewage effluent testing can seem impenetrable to anyone not familiar with the inside of a laboratory. To help with this we’ve put together a quick guide to help with the key elements that you need to know.
We’ve also compiled an ebook, ‘A Guide To Marine Sewage Effluent Testing’ which explores the topic, regulations and solutions in more detail. If you would like to claim a free copy please fill in this form
The Permanganate Value (PV) helps to determine the oxygen requirement of sewage and sewage effluent before it’s discharged. The waste can then be classified to make sure it’s within the necessary limits.
The PV test is designed to show the oxidation of organic material that occurs in natural waters by using potassium permanganate under acidic conditions to accelerate the process. The measurement is usually represented as the quantity of oxygen consumed per litre of water: mg/L O2 or ppm O2.
COD, BOD and TOC
Chemical Oxygen Demand (COD) measures the amount of dissolved oxygen needed to break down the organic material in a water sample.
The Biological Oxygen Demand (BOD) is similar – both measure the presence of compounds – but the BOD value is more detailed as it provides a value for the oxygen needed specifically by bacteria. The higher the BOD value, the larger the amount of food available for oxygen-consuming organisms.
TOC stands for Total Organic Carbon and measures the amount of decaying matter in water. It has been used to analyse water quality and sewage effluent since the early 1970s.
You can estimate a sample’s COD, BOD and TOC values by converting the results of the PV test. Although the results are not definitive, it’s a simplified and low-cost way of carrying out the most essential quality control checks.
Chemical and biological reactions in sewage greatly depend on the amount of acid or alkaline present – the pH. Therefore, regular checks on the pH in your sewage effluent are essential.
These tests are carried out with a Universal test tablet and a printed colour strip that covers a pH range between four and ten. The expected level for your sewage effluents should fall between six and eight.
Free, Combined and Total Chlorine
Chlorine is useful for disinfection as it kills bacteria and viruses – it’s been used in water treatment since the early 1900s. However, it can have a harmful effect on the environment and marine life when released in wastewater.
Free Chlorine is residual chlorine contained in water either as dissolved gas, acid or ions. Combined Chlorine is the concentration of chlorine that has already gone through a chemical reaction – usually with ammonia or organic materials. The Total Chlorine is made up of both of these measurements together.
Bacteria Plate Test
As bacteria aren’t generally visible to the naked eye, a plate test is a way to estimate how many are present in a water sample.
It uses a plate containing a nutrient which allows bacteria to colonise and grow. These will show as a red colour which can then be counted. By using a specific measured amount as a sample, you can then scale up the results to infer the overall content of the effluent.
Escherichia coli (E. coli) is a type of bacteria found in the stomachs of humans and other warm-blooded animals. There are many different strains – most of which are harmless – but some can cause diarrhoea, abdominal pain, fever and vomiting. It can also be fatal for people with weakened immune systems. Checking for E.Coli in sewage effluent is therefore vital.
Testing works in a similar way to the bacterial plate. You take a sample, add specially designed chemicals and then wait for the results which will be either positive or negative. If they’re positive, you should super-chlorinate your water supply and seek further guidance.
Turbidity and Suspended Solids
The turbidity of liquid means how clear it is. Individual particles of suspended solids will cause water to lose its transparency and become murky in a similar way to smoke in the air.
The suspended solids may not be visible to the naked eye so testing the turbidity will give a measure of their content. The test will also keep you informed about the day to day variations in the quality of your wastewater and sewage effluent.
The Royal Commission Standards for Effluents recommend that the suspended solids content of sewage effluent should not be more than 30 mg/l.
Sewage Effluent discharge should always be as close as possible to ambient temperatures as some biological processes are dependent on heat. Chemical reactions – as well as marine life – are very sensitive to even minor variations in temperature.
Checking the temperature of your wastewater is particularly important when it comes to industrial processes as well as the use of hot water in showers, dishwashers, washing machines and other regular domestic appliances.
Sewage Test Kit
If you carry out regular tests of your vessel’s sewage, you can identify issues much earlier and correct them with the minimum of difficulty. This is much more efficient than waiting until a problem develops as repairing faults could have a major impact on your operations.
The equipment in our onboard Sewage Effluent Kit makes sure you meet the regulations in the most simple and effective way possible – the tests are based on those recommended by the Department of the Environment and the Water Research Centre.
The kit provides you with only the most vital components that will allow you to carry out essential quality control checks, saving you time and money and increasing your productivity. The procedures are quick and easy to perform and don’t use complicated equipment so they’re suitable for everyone to use.
Testing your sewage effluent needn’t be complicated or expensive. Martek’s Sewage Effluent Kit makes it easy.
Contact us to find out more.