1. OXYGEN BALANCE OF RIVERS

2. BALANCE ORGANIC MATTER (C, N) DECAY SEDIMENT DEMAND RESPIRATION ATMOSPHERIC DIFFUSION PHOTOSYNTHESIS TRIBUTARIES V dC/dt = IN – OUT + Diffusion – Organic C Decay – Nitrification – Sediment demand + Photosynthesis – Respiration ± Tributaries TRIBUTARIES SOURCES SINKS

3. IMPACTS OF WASTE WATER INLETS BOD 5 emission is increasing, BOD 5 concentration is increasing, dissolved oxygen (DO) concentration is decreasing DO: important indicator element of organic pollution TYPICAL DO CONCENTRATION VALUES Raw waste water: O mg/l Saturation concentration in unpolluted water (based on Henry’s Law): ~ 10 mg/l (at 20 °C ) Protecting fish reproduction:  6 mg/l Different sensitivity of the species and age groups: (e.g. trout: 6-7 mg/l, carp: 4 mg/l) Water quality standards: criterias according to different water uses Classification: in an integrated way (BOD, COD, DO conc., etc.)

4. SIMPLE O 2 BALANCE WASTE WATER ORGANIC CARBON (BOD) HETEROTROPHIC BACTERIA (MINERALIZATION) O 2 DIFFUSION DISSOLVED O 2 CO 2 TWO VARIABLES IN THE TRANSPORT EQUATION (BOD AND O 2 )

5. MINERALIZATION OF ORGANIC CARBON Time (days) O 2 consumption (BOD, mg/l) BOD  5 BOD 5 Organic C content (L, mg/l) Organic carbon content: in term of DO consumption (BOD – Biochemical Oxygen Demand) ~ 2.7 organic C L – Organic C content = remaining oxygen demand L, BOD L 0 = BOI  First order equation L = L 0 exp(- k 1 t) BOD 5 = BOD  - BOD  exp(- k 1 5) = BOD  (1- exp(- k 1 5)) BOD = L 0 - L 0 exp(- k 1 t) = L 0 (1 - exp(- k 1 t)) L0L0

6. DECAY COEFFICIENT (k 1 ) Characterization of intensity of mineralization processes, constant Dimension: 1/day  = 1.04 T k1k1 20 °C 1 Validity! DEPENDENCE ON WASTE WATER TREATMENT TECHNOLOGY 3.20.08Biological treatment 2.00.15CEPT technology 1.60.2Mechanical treatment 1.20.35No treatment fk 1 (T=20 °C)Technology DEPENDENCE ON TEMPERATURE

7. OXYGEN REAERATION (ATMOSPHERIC DIFFUSION) C < C s, diffusion from the atmosphere, C approximates C s C C s – saturation concentration (at a given temperature) Henry’s Law: p = H e C s p – partial pressure of the gas H e – Henry number, function of (T, P, ionic content, etc.) T CsCs Salt content 7.630 920 1015 14.60 C s (mg/l)T (°C) Summer hot periods, heat pollution!

8. C V hh D mol : Molecular diffusion coefficient (m 2 /s) K L : Oxygen transmission coefficient (m/day) k 2 : Specific oxygen reaeration coefficient (1/day) OXYGEN REAERATION (ATMOSPHERIC DIFFUSION) contd. C – DO concentration

9. AFFECTING FACTORS Water depth Flow properties (velocity, turbulence) EMPIRICAL FORMULA Validity, dimension (m/s and m)!!! EPA procedure: k 2  0.1.. 100 1/day (nomogram series) MEASUREMENT Local experiments with injection of volatile gas (ethilene, propane, propilene, krypton) OXYGEN REAERATION COEFFICIENT

10. FOR A RIVER SECTION Q, v L b, C b q, L w, C w Conditions: permanent flow and emission (Q(t), E(t)=const.), far from the source (1D) ORGANIC C Or:Travel time (travelling with the water), assumption: v(t) = const. Calculation of L 0 (1D): Instant mixing !!!

11. DISSOLVED OXYGEN D = C s - C oxygen deficit, assumption: C s = const. Q, v L b, C b q, L w, C w FOR A RIVER SECTION contd.

12. BOD (L) x, t* LbLb L0L0 DO (C) x, t* CbCb C0C0 CsCs C min x crit, t* crit D0D0 D max Q, v L b, C b q, L w, C w FOR A RIVER SECTION contd. BOD AND DO PROFILES L C Exponential decrease Oxygen sag

13. LOCALIZATION OF THE CRITICAL DISTANCE Minimum  0  2  1.5 – 2 days Role of dilution: L 0, D 0  D max, C min !!! More than one pollution source: superposition (because of the linear basic equations) Regulation: iterative calculations (efficiency of removal, decay coefficient)

14. MORE SOURCES Q, v L b, C b q 1, L w,1, C w,1 x, t* L L b,1 L 0,1 C C b,1 C 0,1 CsCs C min x crit, t* crit D 0,1 D max L b,2 q 2, L w,2, C w,2 C b,2 L 0,2 D 0,2 Superposition C 0,2 L C

15. REAERATION STREETER & PHELPS MODEL (1925, OHIO RIVER) BOD DO EMISSION Condition for planning: permanent low flow period Impact assessment of flow dynamics (t crit *, D max )

34. ECOLOGICAL IMPACTS

35. Example: Impact of wastewater discharge on the river oxygen concentration (assumption: 1 D, steady state) Wastewater data:PE 120 000 BOD 5 : 600 mg/lk 1 = 0.42 1/day Kjeldahl N: 120 * 4.57 = 548 mg/l q = 120 000 * 0.1 = 12000 m 3 /day = 0.14 m 3 /s Stream:Background concentration: L b = 5 mg/l, C b = 8 mg/l T = 25 C, v = 0.5 m/s, Q = 15 m 3 /s, Cs = 8.4 mg/l k 2 = 0.7 1/nap Initial concentration: L 0 = 16.6 mg/l, D 0 = 0.47 mg/l Critical distance: t crit = 1.9 nap, x crit = 82 km C min = 3.6 mg/l Dilution effect

36. Minimum oxygen contrentation (mg/l) No treatmentHigh loadedLow loaded Total oxidation activated sludge

37. STREETER-PHELPS (1925) EXTENSIONS 1.Separation of dissolved and particulate organic matter fractions 2.Sediment oxygen demand 3.Nitrification 4.Photosynthesis, respiration DETAILED DESCRIPTION OF DO BALANCE

38. SEPARATION OF DISSOLVED AND PARTICULATE ORGANIC MATTER FRACTIONS L p = f p Lparticulate (settling due to gravity) L d = f d Ldissolved (biological decay) t* L0L0 settling decay L Extension of DO equation: dC/dt = - k d L

39. SEDIMENT OXYGEN DEMAND CAUSES -Settling particles of the waste water -Dead aquatic animals and plants and leaves at the bottom -Algae settling IMPACTS OF SEDIMENT HAVING HIGH ORGANIC C CONTENT -Upper part of the sediment: aerob decomposition  oxygen abstraction from pore water  hihgh concentration gradient  diffusion -Lower part: continuous oxygen lack, anaerob conditions  CO 2, CH 4, H 2 S formation -Gas formation  rising bubbles, sediment flotation -Aesthetic problems DESCRIPTION constant, area-specific demand – S (g O 2 / m 2,day) 0.05-0.1 (0.07)River mouth sediments 0.2-1 (0.5)Sandy sediments 1-2 (1.5)Sediments far from the source 2-100 (4) Sediments near the pollution source S (g O 2 / m 2,day) Sediment character Extension of DO equation:

40. NITRIFICATION 5 20 days BOD LCLC LNLN KJELDAHL-N (Organic N, NH 4 -N, NO 2 -N) Two steps: Nitrosomonas2NH 4 + + 3O 2  2NO 2 - + 2H 2 O + 4H + Nitrobacter2NO 2 - + O 2  2NO 3 - 3.43 g O 2 1.14 g O 2  4.57 g O 2 L N = 4.57 Kjeldahl-N CONDITIONS Nitrification (obligate aerob, autotrophic) bacteria, Non-acid environment (pH > 6), Presence of oxygen, DO > 1-2 mg/l, Absence of toxic substances Simplest description: L C+N = L C + L N – integrated BOD Extension of DO equation: dC/dt = - k 1 L C+N

41. 1 2 SIMPLE (TN) DETAILED (N forms) N1N1 N2N2 N3N3 Settling Denitrification Assimilation by plants Hydrolysis, Ammonification Nitrification O2O2O2O2 N 1 – organic N, N 2 – NH 4 -N N 3 – NO 2 -N, NO 3 -N N1N1 N2N2 N3N3 Extension of DO equation: dC/dt = - k 23 4.57 N 2 NITRIFICATION contd. Extension of DO equation: dC/dt = - k N L N L N = 4.57 TKN t t t

42. PHOTOSYNTHESIS, RESPIRATION 6CO 2 + 6H 2 0  C 6 H 12 O 6 + 6O 2 Light, chlorophyll PHOTOSYNTHESIS (P, m O 2 / m 3, day) RESPIRATION (R, mg O 2 / m 3, day) t (h) P, R 24 t (h) O2O2 24 CsCs supersaturation CC t1t1 t2t2 PaPa PmPm Daily average oxygen production: photoperiod Extension of DO equation: Measuring: method of „dark-light bottle” Calculation: based on the Chl-a content Respiration of aquatic plants RaRa

43. BASIC DIFFERENTIAL EQUATIONS ORGANIC CARBON DECAY NITRIFICATION (simple description) OXYGEN CONCENTRATION

44. OXYGEN DEFICIT AND DISSOLVED OXYGEN CONCENTRATION INITIAL DEFICIT ORGANIC CARBON DECAY NITRIFICATION SEDIMENT OXYGEN DEMAND PHOTOSYNTHESIS RESPIRATION OXYGEN CONCENTRATION

45. CALCULATION OF ANAEROB CONDITIONS High waste loads Temporary or permanent anaerob conditions Anaerob decay, gas formation, dissolution of metals C t* L x1x1 1. Start of anaerob stage: x 1 (C ~ 0) 2. Anaerob stage (dC/dt = 0, C = 0): x1x1 L1L1 3. End of anaerob stage: x 2 x2x2 L2L2 x2x2 Linear function