Water & Liquid Compost Analysis Methods

PARAMETER

METHOD

Principle

Water pH

Potentiometric

pH is determined by using a high impedance voltimeter. The potential between two electrodes is measured using the voltmeter on a water/liquid

sample

Water EC

Potentiometric

The electrical conductivity indicates the amount of soluble (salt) ions in soil. The determination of electrical

conductivity (EC) is made with a conductivity cell bymeasuring the electrical resistance water sample

Water P, Ca, Mg, K, Na, Mn, Fe, Cu, Mo, B, Zn, S,

Si +Heavy metals (As, Cd, Cr, CO, Pb, Hg, Ni,

Se)

Atomic Emission spectrometry (ICP- OES)

When plasma energy is given to an analysis sample from outside, the component elements (atoms) are excited. When the excited atoms return to low energy position, emission rays (spectrum rays) are released and the emission rays that correspond to the photon wavelength are measured. The element type is determined based on the position of the

photon rays, and the content of each element is determined based on the rays' intensity.

Ammonium

Colorimetric

Ammonia reacts with hypochlorite ions generated by the alkaline hydrolysis of sodium dichloro-isocyanurate to form monochloramine. This reacts with salicylate ions in the presence of sodiumnitroprusside at around pH 12.6 to

form a blue compound. The absorbance of this compound is measured

spectrophotometrically at wavelength 660nmand is related to the ammonia

concentration by means of a calibration curve.

Nitrate Nitrogen

Colorimetric

Nitrate is quantitatively reduced to Nitrite (NO2) by a redox reaction with a granulatedcadmium metal in the presence of a suitablebuffer. The nitrite thus produced is then reacted with the griess reagents to form a

strongly coloured azo dye that is measured spectrophotometrically at 540nm.

Chloride

Colorimetric

Chloride reacts with mercury (II) thiocyanateto form a soluble non ionic

compound. The thiocyanate ions released reactin acid solution with iron (III)

nitrate to form a red/brown iron (III) thiocyanate complex. The resulting intensity of the stable colour produced ismeasured spectrophotometrically at

a wavelength of 480nm and is related to the chloride concentration by means

of a calibration curve.

Bicarbonate

Colorimetric

Alkalinity is determined by measuring the absorbance of the complex formed when a sample is reacted with bromophenol blue in a pH 3.5 phthalate

buffer, spectrophotometrically

at 400nm.

Fluoride

Colorimetric

Fluoride is allowed to react at a pH of 4.5 withthe red chelate formed between cerous nitrateand alizarin fluorine blue. The absorbance of the resulting blue complex is measured at wavelength 620nm.

Turbidity

Turbidimeter

Turbidity in a liquid is caused by the presenceof finely divided suspended particles. When a beam of light is passed through a sample, theloss of intensity of transmitted light due to thescattering effect of particles suspended in it ismeasured and reported as turbidity.

Total Coliforms & Faecal E.Coli

ISO 9308-2:2012

method - Enumeration

Enumeration of Escherichia coli and coliform bacteria -- Part 2: Most probable number method

BOD

5 days incubation

BOD is measured using a respirometer, whereby measurement using OxiTop is basedon pressure measurement in a closed system.Microorganisms in the sample consume the oxygen and form CO2; the CO2 is absorbed byNaOH, creating a vacuum that can be

measured as a mg/l BOD value over a five (5)day period

COD

Closed Reflux Colorimetric method

Measurement of organic constituents which are oxidized during a heating of 2 hours at 150 °C by chromosulfuric acid with silver sulfate as a catalyst. The dichromate present in the reaction mixture is the oxidative agent. Duringthe reaction the green chromate ion is formed from yellow dichromate.

This increase in absorption at 600 nm is in relation to the amount of oxidizable substances in the sample.

Oil & Grease

Partition- Gravimetric Method

Dissolved or emulsified oil and grease is extracted from water using an organic solvent, in this case petroleum ether.

TDS & TSS

Gravimetric

The total dissolved solids is determined by filtering a measured volume of sample through a standard glass fiber filter. The filtrate (i.e., filtered liquid) is then added to a pre- weighed ceramic dish that is placed in a drying oven at a temperature of 103 C.

To measure TSS, the water sample is filtered through a pre-weighed filter. The residue retained on the filter is dried in an oven at

103–105°C until the weight of the filter no longer changes.