How to determine MLSS

First measure a certain volume of water sample, then filter it with filter paper, and then put the filter paper into an oven to dry it to a constant weight. Subtracting the weight of filter paper is the weight of sludge, divided by the volume of water sample.

Specific operation:

Instruments and laboratory supplies

1. quantitative filter paper

2. muffle furnace

Step 3: oven

4. Dryer, desiccant is indicated by color.

5. Analytical balance with sensitivity of 0. 1mg.

Experimental steps (actual operation in brackets)

1. The quantitative filter paper is dried at 103- 105℃, cooled during drying, weighed, and repeated until a constant weight is obtained or the weighing loss is less than 4% of the previous weighing; Weight is m0; (After drying for 8 hours, put it into a dryer for cooling, and weigh it as the final value or directly count it as 1g with φ 12.5 filter paper. )

2. Filter the sample 100ml with filter paper in 1, put it in the oven of 103- 105℃, take it out, cool it to the equilibrium temperature in the dryer, weigh it, and repeatedly dry it so that the constant weight or weight loss is less than 5% or 0.5mg of the previous weighing (.

SS=(m 1- m0)/0. 1 (after drying for 8 hours, put it in a dryer for cooling, and then weigh it to the final value).

3. Put the clean crucible into the oven to dry for one hour, take it out and put it into the drying room to cool to the equilibrium temperature, and weigh it with the weight m2;

4. Put the filter paper and mud in 2 into the crucible in 3, then put it into a cold muffle furnace, heat it to 600℃ and burn it for 60 minutes, then put it into a dryer for cooling and weighing, m3; (Starting from a temperature of 600℃)

VSS =[(m 1+m2-m0)-m3]/0. 1

MLSS: the total amount of activated sludge solids in unit volume mixed liquor (mg/L), and MLVSS refers to volatile suspended solids in mixed liquor. Domestic sewage generally MLVSS/MLSS=0.7. Measuring MLSS requires qualitative filter paper (non-quantitative), electronic analytical balance, oven, dryer, etc. Take 100ml mixed solution and filter it with filter paper. After the temperature in the oven rises to the set value between 103- 105, put the filtered filter paper in the oven for 2 hours, take it out and put it in the dryer for half an hour. After weighing, subtract the weight of the filter paper, and measure the weight of the filter paper by the same steps as above. The experiment must be carried out in strict accordance with the above operations, otherwise it will be biased.

Common determination methods of MLSS and MLVSS

1. Definition:

MLSS: mixed liquid suspended solid. Refers to the concentration of activated sludge in the mixed liquor of aeration tank, that is, the total weight of activated sludge solids in the mixed liquor per unit volume.

MLVSS: indicates volatile suspended solids in mixed liquid. The amount of organic matter (mixed liquor suspended solids) in MLSS is called MLVSS.

2. The meaning of indicators:

MLSS and MLVSS are indicators for indirectly measuring microbial biomass of activated sludge.

3. Collection, preservation and matters needing attention of water samples

The sampling position is located at the outlet of the aeration tank; The water depth of the aeration tank is 3. 1m, so sampling should be taken at 0.78m below the liquid surface, and the actual sampling position should be in the center of the sampling section.

4. Detection method: (residue)

Principle: Dry the evenly mixed mixed liquid in a constant weight evaporating dish with steam bath or water bath, and then dry it to constant weight in an oven at 103 ~ 105℃, and the added weight is MLSS. MLSS samples were determined and burned at 600℃ in muffle furnace, and the converted weight was MLVSS.

5. Method steps:

⑴ MLSS:

① Weigh the evaporating dish with constant weight as W 1 (constant weight: the evaporating dish is dried in an oven at 105℃ 1h and cooled in a drying dish for 30min).

② Measure a certain volume of mixed liquid (50ml), put it in a centrifuge, and centrifuge at 2500rpm for 65438±05min.

(3) Carefully remove the supernatant, and then transfer it to a constant weight evaporating dish.

(4) Evaporating the evaporating dish in the water bath at 100℃, moving it to the air drying oven at 103 ~ 105℃ for 2 hours, standing in the drying oven for 30 minutes, and recording the weight W2.

⑵ MLVSS:

(1) Put the dry sludge of MLSS and the evaporating dish on the electric furnace for carbonization until there is no smoke.

(2) Burning in a muffle furnace at 600℃ for 30-40 minutes, and then cooling to 1 10℃.

(3) Put it in an oven at 105 ~ 1 10℃ for 30 minutes.

(4) put it into a dryer and cool it for 30 minutes.

⑤ Weighing record W3

6. Data collation

Calculation formula: mlss = (w2-w1)/v *1000.

MLVSS=(W2-W3)/V* 1000

The results show that:

MLSS and MLVSS are represented by g/l.

MLVSS/MLSS is expressed as a percentage.

7. Error analysis

The residue after drying at 103 ~ 105℃ retains crystal water and partially absorbs water. Organic matter volatilizes less, so MLSS can be expressed more accurately.

(1) The evaporating dish has a constant weight, and the difference between the two weighing is ≤ 0.0005g..

(2) mlss has constant weight, and the difference between the two weighing is ≤ 0.0005g.