Organic waste and effluents characterisation

The chemical demand for oxygen is the quantity of oxygen necessary to oxidize by chemical way the organic matters contained in one liter. It is expressed out of Mg O2/L or kg. This measurement enables us to appreciate the organic load of an effluent or a waste to be developed



Dry matter

The dry matter is the remaining matters after the passage of a sample to 105°C during 24 hours. The dry matters include at the same time the suspended matter and salt

Volatile matter

The volatile matter corresponds to the proportion of dry matter of a given sample, evaporating between 105°C and 550°C in a 4 hours interval. This measurement represents the quantity of organic matter of the dry residue.

Hard organic load

The “hard organic load” is the share of organic load known as “residual” i.e. which cannot be metabolized by the bacteria. The principle of the measurement of the “organic load” lies on the capacity of aerobic bacteria to degrade a given substrate. The protocol of the experiment consists in the follow-up of the organic load of an effluent during time in an agitated and aired engine, in contact with activated sludge.

Nitrogen (NTK)

The NTK, also called Kjeldhal nitrogen, corresponds to phosphatous nitrogen (NH4+) and organic nitrogen. It does not take into account, contrary to total nitrogen, nitrogen resulting from nitrates and nitrites.This value is important to appreciate the balance of the nutrients (ratio Carbon/Nitrogen/Phosphorous) for the anaerobic degradation of a given waste.

Phosphorous

The proportioning of total phosphorus of a waste is carried out by means of a destruction of the organic matter in sulphuric medium with a nitro-perchloridric mixture. As the nitrogen concentration, the concentration out of phosphorus must be appreciated according to the percentage of carbon of waste to determine good balance in nutrient of a waste.


Fibres

The fibres are proportioned according to the method of VAN SOEST (fractions ADF, NDF and lignin) as well as the extraction and proportioning of rough fibres (cellulose WEENDE). This characterization makes it possible to have the first measurement of the bio deterioration of a waste.

Grease (Extractable Matters with Hexane)

Greases are lipids mainly made up of fatty-acids (acid aliphatic the number of carbon is higher than 4) and of glycerines. The glycerines are fatty-acids related to a glycerol molecule by bonds esters. The proportioning of the MEH makes it possible to estimate the quantity of greases contained in a waste. The technique used consists of an extraction of the total lipids by a mixture of hexane and methanol.

Protein

A protein is an assembly of amino-acids bound by peptide connections. We speak about protein when more than 100 amino-acids are dependent within a chain of amino-acids. Proportioning is carried out thanks to the method of Lowry which makes it possible to quantify the peptide connections. Based on the biuret reaction, it uses the reduction of Cu2+ in Cu+.

Sugar

The content in glucids is determined by the anthrone method. This proportioning makes it possible to measure reducing total sugars. Proportioning with the enthrone (or oxo-9-dihydro-10-anthracene) measurement the functions carbonyl (C=O). It is based on the intermolecular dehydration of the oses in hot medium acid. The furfuralic derivatives obtained (5-hydroxyméthyl-furfural for hexoses) condense with the anthrone for given coloured products (green for hexoses).

Agronomic value of the sludge

With the aim of knowing the agronomic value of sludge, the following measurements are taken: Sulphur, Copper, Sodium, Magnesium, Potassium, Phosphorus, Calcium. These measurements are compared with the values thresholds to which the organic soil conditioners must answer according to standard NF U-44-051.

The Volatile Fatty-acids correspond to the following acids: acetic, propionic, butyric, etc…. They are intermediaries of the reaction of anaerobic digestion but they can be also inhibitors with certain concentrations (generally beyond 2 - 3 g.L-1). The nature and the concentration of the volatile fatty-acids (AGV) are given using a chromatograph GC800 (Fisons Instruments) equipped with a detector with ionization of flame and with an automatic frontier runner of samples AS800 (Fisons Instruments).

DBO5

The DBO5 is the quantity of oxygen necessary to the aerobe micro-organisms to ensure the oxidation and the stabilization of the biodegradable organic matters present in 1 liter. By convention, the DBO5 is the value obtained after 5 days of incubation to 20°C within darkness, expressed in milligrams per liter.