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

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.

• Analytical balance - capable of weighting to 0.1 mg
• Drying Oven for use at 103 – 105°C
• Muffle Furnace for use at 550°C
• Aluminum or ceramic dish (permanently labeled)
• Crucible or evaporating dish tongs
• Heat resistant gloves
• Desiccator and desiccant that contains a color indicator for moisture content
• Cotton gloves

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).

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

The following must be recorded on the data sheet:

• Sample identification (source, name, and date(s) of collection)
• Analyst(s)
• Raw data
• Final results with correct units (reported to nearest 0.1%)
• Description of unusual sample characteristics
• Replicates are to be listed in an orderly cluster

Replicate analyses should yield RSD’s less than 5% for the entire data set.

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.

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.

Where:

• Know safety procedures for solids anlayses
• Know how to fill out raw data sheets
• Know where to find equipment / supplies
• Understand equipment used to perform total solids analyses
• Analytical scales
• Level of sensitivity
• How to tare weights
• Desiccator
• Muffle furnace
• Understand analysis procedures used to perform total solids analyses
• Need for well mixed samples
• Means for taking sample aliquots
• Drying times
• Cooling times
• Know how to calculate total and volatile total solids results
• Understand quality control procedures
• Need for quality control
• Calculation of mean and %RSD
• Know how to clean ceramic or aluminum dishes

• Prepare ceramic or aluminum dish (if not already done)
• Collect the sample
• Obtain dry weight of ceramic or aluminum dish (tare weight)
• Transfer appropriate volume or mass of sample to ceramic or aluminum dish
• Place ceramic or aluminum dish and sample in oven to dry
• Move ceramic or aluminum dish and sample residue to desiccator to cool
• Obtain dry weight (constant if necessary) of ceramic or aluminum dish and sample residue
• Calculate total solids
• Place ceramic or aluminum dish and sample residue into muffle furnace
• Move ceramic or aluminum dish and sample residue to desiccator to cool
• Obtain ashed weight of ceramic or aluminum dish and sample residue
• Calculate volatile total solids
• Prepare ceramic or aluminum dish for next or subsequent use