This method describes how to measure the surface tension of wastewater using a tensiometer.
Wastewater generated in the industrial production of beer and food
The force measured in this analysis is exerted by the surface tension. The surface tension can be measured either as the force on a plate oriented perpendicular to the surface of the liquid and thoroughly wetted by it (static method) or the force that is required in order to pull out a horizontally suspended rod or ring from the liquid surface (quasi-static method).
Wastewater generated in the industrial production of beer and food
The water sample is diluted with oxygen-rich water “free of oxidizable organic substances” so that after the incubation period there is still at least 2 mg oxygen per liter left in the water. Afterward, the dissolved oxygen in the diluted sample should be determined immediately and then again after five days using an iodometric method or with oxygen electrodes. The difference between the two values yields the BOD5 (taking into account the dilution factor).
Determination of organic acids using ion chromatography
This method is suitable for beer, wort, green beer, NAB, water and wastewater
Separation by ion chromatography followed by conductivity detection.
Wastewater generated in the industrial production of beer and food
Well-mixed wastewater is poured into an Imhoff funnel, and the volume of sludge is recorded using the volumetric scale on the graduated cylinder after a settling time of two hours.
After decanting the supernatant, the deposits are quantitatively transferred to a platinum dish in which, after drying at 105 °C, the dry residue after evaporation is determined by weight.
After annealing in a muffle furnace at 550 °C for 30 min, the ash content is determined gravimetrically.
The annealing losses are calculated from the difference in weight between the dry residue after evaporation and the ash content.
This method describes how to determine the chemical oxygen demand in wastewater through oxidation with potassium dichromate.
Potassium dichromate is added to the acidified sample as an oxidizing agent along with silver sulfate as a catalyst; mercury sulfate is also added to prevent the formation of elemental chlorine from chlorides. After oxidation of the organic substances in the sample (the dichromate ion is reduced to the chromium(III) ion in an acidic solution), the chromate required to achieve this is determined through reverse titration of the excess potassium dichromate with iron(II) solution (adjusted) against ferroin as an indicator [1].
Cr2O72- + 6 e- + 14 H3O+ → 2 Cr3+ + 21 H2O
Cr2O72- + 6 Fe2+ + 14 H3O+ → 2 Cr3+ + 6 Fe3+ + 21 H2O