1 IV. Wastewater Treatment Topic IV. 4. Pollution Loads on the Receiving Water. Wastewater Quality Parameters - BOD, COD, TOC, PE. Oxygen Balance in the Receiving Water Pollution Load Definition: Mass of a definite pollutant, released in definite period (day, month, year) into the receiving water with the wastewater emissions. Kinds of pollution loads: §Suspended solids - SS §Organic substances containing carbon - BOD, COD, TOC §Substances containing nitrogen - N tot, N org, NH 4 -N, NO 3 -N §Substances, containing phosphorus - P tot, P org, PO 4 -P, P 2 O 5 -P

2 Wastewater Quality Parameters - BOD, COD, PE Biochemical Oxygen Demand - BOD, g/m 3 Definition: Mass of dissolved oxygen utilised in definite time by the aerobic micro-organisms during processes of dissimilation of organic substances, containing carbon. Particularities: §BOD is a complex measure, indicating indirectly availability of biodegradable pollutants mass concentration §BOD reflects only biodegradable part of carbonaceous organic substances §BOD reflects only such a part of carbonaceous organic substances, which is utilised in processes of dissimilation (breathing) §Biodegradable organic substances utilised by the aerobic micro- organisms in the processes of assimilation (cell mass building) is not reflected by BOD

3 Biochemical Oxygen Demand - BOD Fazes of aerobic oxidation of organic substances

4 Biochemical Oxygen Demand - BOD BOD Kinetics;

5 Chemical Oxygen Demand - COD, g/m 3 Definition: Mass of the oxidiser utilised in oxidation of (almost) all the organic substances in water. Particularities: §COD is associated with potassium dichromate - K 2 Cr 2 O 7 as an oxidiser in presence of silver sulphate - AgSO 4 as a catalyzer §Similar parameter, called oxidability is associated with potassium permanganate - KMnO 4 as an oxidiser

6 Total Organic Carbon - TOC, g/m 3 Definition: Carbon mass of the organic substances in water/wastewater Analytical determination: §Procedure as for COD determination §Procedure for C-fixing in BaCO 3 Particularities: §TOC is a general measure for organic pollutants mass in water/wastewater (similar to COD function, but more precise) §TOC reflects both biodegradable and biorefractory organic substances in water/wastewater

7 People Equivalent - PE Definition: Number of population releasing the same pollution load as the one released with definite industrial wastewater emission Q ind - industrial water quantity, m 3 /d Q dom - domestic water quantity, m 3 /d C ind - pollutant concentration in industrial wastewater, g/m 3 a - pollutant daily mass per citizen (pollutant norm), g/d.ca Particularities: §PE differ according to the kind and norm of the pollutant §PE is a general and common measure of industrial pollution load

8 People Equivalent - PE Pollutants norms §Suspended solids l Non-settled wastewater- a = 65 g/d.ca l Settled wastewater - a = 40 g/d.ca §BOD 5 l Non-settled wastewater- a = 60 g/d.ca l Settled wastewater - a = 40 g/d.ca §Nitrogen - a = g/d.ca §Phosphorus (as PO 4 + ) - a = 4,4 g/d.ca

9 Oxygen Balance in the Receiving Water §Rate of dissolved oxygen consumption for biodegradable organic pollutants dissimilation in the receiving water (BOD kinetics) §Rate of dissolved oxygen recovering in the receiving water (reaeration) §Net rate of dissolved oxygen concentration change in the receiving water

10 Oxygen Balance in the Receiving Water Streeter - Phelps Equation (integral of the last differential equation)

11 Oxygen Balance in the Receiving Water Graphical Interpretation of the Streeter-Phelps Equation