Bench Top Digestion Test for Sludge Reduction
(9 August 2015)
Purpose
To measure the reduction in accumulated sludges and scums in on-site treatment systems.
Materials
Liquid effluent:
20 L of wastewater liquid from a municipal wastewater system essentially collecting and treating residential wastewaters. The liquid should be taken upstream of the final screens before treatment.
The pH of the wastewater liquid should be between 6 and 9 - adjust the pH if necessary.
Measure and record the TSS of the wastewater liquid.
The liquid should be passed through a [5 mm screen] to ensure the removal of larger pieces of solid materials
Sludge:
10 L of sewage sludge from a municipal wastewater system essentially collecting and treating residential wastewaters.
Test equipment
Six 2.8 L flasks with foam stoppers
Six US Standard #18 testing sieve, 20 cm in diameter
One Orbital shaker table with a 1” or 2” orbit, capable of 0 -100 rpm speed with clamps
Procedure
Take 40 mL of sewage sludge and dry it to determine the dry weight using a drying pan (see Drying Process).
Place 40 mL of undried sewage sludge in each of six 2.8 L flask with 1.5 L of wastewater liquid.
Place a sample of the additive (in accordance with the mixing instructions of the manufacturer to achieve the expected dilution ratio) in each of three 2.8 L flasks and mark those flasks as the test flasks. Take three other flask and mark them as control flasks.
Flasks should be clearly numbered or otherwise identified by treatment.
Stir the contents of each flask to create a dispersion of the sludge within the wastewater liquid.
Place and secure the six flasks on the orbital shaker table, set the orbital speed at [20] rpm for a 2” orbital shaker
Incubate with continuous shaking for 14 days at room temperature (22 ± 3°C).
Periodically, inspect the flasks and rinse any solids entrapped on the sides back into the mixed liquor using a squirt bottle with tap water. Additionally, replace any water that has been lost to evaporation. If rinsing is insufficient to remove a build-up of solids, use a scraper to return the solids to the mixed liquor.
After 14 days, remove the flasks from the orbital shaker table.
Pour the contents of contents of each flask through the Standard #18 sieve.
Collect the liquid portion of the contents separately and measure the TSS.
Remove solid materials from the sieve and place into labelled (tared) drying pans.
Drying Process
Dry the samples in an oven between 40 and 50 o C for several hours or overnight.
Transfer the samples from the oven to a desiccator and allow to them to cool.
Weigh the samples and record the sample weights.
Return the samples to the oven for approximately 30 minutes and once again allow them to cool in desiccator and determine their weight.
Repeat this process as necessary until they reach constant weights.
Record the dry weight of the 6 samples (three with additives treatment, three control samples).
Compare the results with the originally dried sludge sample.
Measure of performance
All six dried samples should have a weight lower than the originally dried sludge sample.
The average weight of the dried material of the additive treated samples should be [10%] lower than the average dried weight of the control samples.
The TSS levels of the liquid should be less than the original TSS level of the wastewater liquid (fluctuation measured and reported in %).
Note
This method does not propose to collect gases released through the incubation/digestion process.
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