Page 62 - March 2020 - WT Site

2. Calculate the amount of nitro- gen that can be denitrified
with the wastewater: With upstream denitrification and a V :V
AT
D
ratio of 0.5, the denitrification capacity (according to Table 7) is Inflow [m /d]
3
C = 0.15 kg NO -N /kg BOD .
Deni 3 D 5
BOD 5 infl aer [mg/L]
S , = C × BOD = 0.15 × 110 mg/L = 16.5 mg/L
NO3-N D Deni 5 inflaer TN [mg/L]
infl aer LATON
This means that 16.5 mg/L NO -N can be denitrified with the P tot infl aer [mg/L]
3
existing biological treatment.
BOD : TN = 110:45 =
5 infl aer. infl aer
Causes/Origin of Possible Corrective Action Table 5: Average Daily Values of a Municipal Wastewater
wastewater consequences Treatment Plant
• Landfill leachate, • Inadequate • Addition of C sources
wastewater from denitrification to improve Average
composting and residual (high nitrate values denitrification daily values
waste treatment facilities in the outflow) • Use chemicophysical
and the chemical industry • High COD in the methods (ozone N incorporated in biomass (5 % of BOD infl aer) 5.5mg/L
5
• Considerable reduction outflow of the treatment, activated N (e = assumed target quantity in the outflow) 2mg/L
in BOD5 in the long wastewater carbon filter, membrane org.e
sewage net work in treatment plant technology) for poorly NH -N (e = target quantity in the outflow) 0mg/L
e
4
summer biodegradable and
• Deterioration of NO -N (e = target quantity in the outflow) 8mg/L
• Intensive primary bio-P non-biodegradable 3 e
treatment of the substances Sum 15.5 mg/L
wastewater
Table 6: Calculation of Amount of Nitrogen that is not to be
Table 4: Causes and Effects of Unfavourable COD:BOD Ratios
∑
5 Denitrified (Σ Nn.d.)
Regulating the substrate dosage by means of C Deni (Denitrification capacity in
NO -N measurements V /V AT kg NO -N /kg BOD )
D
5
D
3
3 Volume Deni /
Volume Aeration
Upstream Simultaneous and
3. Calculating the external substrate requirement denitrification intermittent denitrification

The still to be denitrified N content is the total added nitrogen 0.2 0.11 0.06
minus the amount of nitrogen that is not to be denitrified minus 0.3 0.13 0.09
the amount of nitrogen that the plant can denitrify:
0.4 0.14 0.12
S = TN - ∑N - S = 45 mg/L - 15.5 mg/L - 0.5 0.15 0.15
NO3-N, D, Ext Inflow n.d. NO3-N, D
16.5 mg/L = 13 mg/L
Table 7: Denitrification Capacity in Accordance with ATV-A131
0
To denitrify the remaining 13 mg/L nitrogen, the microorganisms (guideline values for dry weather and temperatures from 10 to 12 C)
in the activated sludge must be provided with an additional
source of carbon. A daily wastewater volume of 10,000 m has a Acetic acid Methanol Ethanol
3
nitrogen load of 130 kg. According to DWA Work Sheet A131, kg/kg 1.07 1.50 2.09
COD
the external carbon requirement is 5 kg COD/1 kg NO -N. This
3 TOC kg/kg 0.40 0.38 0.52
means that, for complete denitrification to occur, 650 kg COD BOD kg/kg 0.70 0.96 1.35
are needed per day. If the additional carbon is provided in the 5
form of acetic acid, the data provided in Table 8 indicate that 607 Density kg/m 3 1,060 790 780
kg would have to be added each day. The targeted dosage is based
Table 8: External Carbon Sources for Calculating the
on the NO -N values.
3 Necessary Dosage

64 Water Today - The Magazine March 2020