Dobrna, Slovenia
Dobrna, Slovenia, 2009
The Dobrna Wastewater Treatment Plant (WWTP) ensures preliminary mechanical and secondary biological treatment of sewage from 4000 Population Equivalents (P.E.). The raw sewage is collected from the area of DOBRNA and conveyed to the WWTP by a combined sewerage system.
WWTP consists of mechanical pre-treatment section, two sections for biological treatment – older one with capacity of 1 800 P.E. and one new designed and executed by Hydrotech with capacity of 2 200 P.E.. For separation of treated water and activation sludge new sedimentation tank was constructed with hydraulic capacity of 4 000 P.E.. Existing sludge holding tank is used for surplus sludge. The treated final effluent is conducted to the river.
For nutrients removal pre-denitrification and phosphorus precipitation processes are included in the biological treatment process.
Graph: Design (legislative requirements) and operational removal efficiencies parameters
Inlet
COD
TSS
Ntotal
Ptotal
Design parameters
400 mg/l
233 mg/l
37 mg/l
8,4 mg/l
Operational phase
390 mg/l
214 mg/l
37,4 mg/l
5,7 mg/l
Outlet
COD
TSS
Ntotal
Ptotal
Legislative requirements
75 mg/l
30 mg/l
15 mg/l
2 mg/l
Operational phase
20 mg/l
4 mg/l
2 mg/l
3,8 mg/l
Efficiency
COD
TSS
Ntotal
Ptotal
Legislative requirements
81,3 %
87,1 %
59,5 %
76,2 %
Operational phase
94,9 %
98,1 %
94,7 %
33,3 %
Parameters
Project
Capacity:
4 000 PE
1 200 m3/d
Type of wastewater:
Municipal WWTP
Technology:
-
Mechanical pre-treatment: combined unit for mechanical pre-treatment
-
Secondary treatment: Selector, denitrification, and nitrification tanks followed by secondary sedimentation tank
-
Phosphorus precipitation
References
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