% Total Solids, % Volatile Total Solids

Reference:

Standard Methods; 2540 A, 2540 B, 2540 E, 2540 G

Scope and Applications

Total solids are the sum of suspended solids and dissolved solids. Total solids analyses are important for assessing wastewater treatment processes such as digester efficiencies and sludge cake processing parameters. These tests are commonly performed on sludge samples when the concentration of solids is greater than 10,000 mg/L or 1%, thus making them very difficult to filter.

The total solids are composed of two components, volatile and fixed solids. The volatile solids are organic compounds of animal or plant origin. Biological processes can treat these. When volatile solids are referred to in this manual, we are actually referring to the volatile total solids, or the portion of the total solids that are volatile. The fixed solids are things such as sand, gravel, and salt.

Apparatus

Reagents

The only reagent that may be needed for % total solids analysis would be deionized water, but even this is not necessary. This is because there is not a filtering step and any material in or on the dish at the start of the analytical procedure can be expected to remain constant through the process, (after the initial ashing of the dish during dish preparation).

Storage / Preservation

Samples may be stored in a plastic or glass container and kept for 7 days at 4 C. See sample storage and preservation table.

 

Raw Data Sheet Format

The following must be recorded on the data sheet:

Quality Control Requirements

Replicate analyses should yield RSDs less than 5% for the entire data set.

Procedure

Dish Preparation

  1. Pre-wash the aluminum or ceramic dish.
  2. Place the dish in a 103 -105 C oven to dry. If volatile total solids are to be analyzed, move the dry dishes into a 550 C muffle furnace for 15 minutes; if the volatile portion does not need to be determined, place the dishes into a desiccator to cool and skip step 3.
  3. Remove the dishes from the muffle furnace and place on a heat resistant surface. The surface temperature of the dish must be greater than 103 C when placed into the desiccator.
  4. Cool the dishes thoroughly in a desiccator before use. Prepared dishes should be stored in a desiccator.

Sample Analysis % Total Solids

  1. Weigh the dish (at room temperature) on an analytical balance. Use crucible tongs or wear lint free cotton gloves to transfer the dish from the desiccator to the balance pan. Handling the dish with your bare fingers may transfer oils and moisture from the skin.
  2. Record the weight of the dish.
  3. Thoroughly mix the sample to be analyzed. Carefully measure the mass of sample transferred to the dish.
  4. Place the dish in the oven to dry for one to two hours at 103 C. Depending on the mass of the sample and the amount of water in the sample, it may take longer for the sample to dry.
  5. When the sample is dry, transfer the dried dish to a desiccator to cool. When the dish has cooled sufficiently it should not feel warm to the touch on the inside of your forearm.
  6. Weigh the dried and cooled dish on an analytical balance. Record the weight. If the sample is not going to be used for regulatory purposes, it may be acceptable to use this weight as the final dry weight.
  7. Return the dish to the drying oven for another thirty minutes. Cool, desiccate, reweigh and record weight. Repeat this procedure until the change in the weight of the residue remains within 4% or less than 0.5 mg from one weighing to the next. (This is referred to as constant weight.) Record the final weight on the benchsheet and calculate the % total solids.

Calculations

Where:

Sample Analysis % Volatile Solids (or % Volatile Total Solids)

  1. Place the dish and residue produced by %TS analysis in a muffle furnace at a temperature of 550 C for 15 to 30 minutes. The process is not complete until the heat has removed any carbon or soot deposit (black glaze) on the dishes.
  2. Remove dish with ash from muffle furnace, cooling partially, then placing in a desiccator until cooled.
  3. Weigh cooled dish and ash on an analytical balance and record weight. Be careful when opening the desiccator. The cooled air (gas) inside the desiccator will have created a vacuum, sudden opening of the desiccator may cause the loss of some of the ash or fixed solids from the dish.
  4. Repeat ignition, cooling and weighing until a constant weight is obtained or until weight loss is less than 4% of the previous weight.
  5. Record the final ashed weight on the benchsheet and calculate the % volatile total solids.

Calculations

Where:

 

Goals for a New Analyst Performing %TS / %VTS Analyses

 

% Total Solids Analysis; the Tips for Techs version