Rabea-Luisa, Schubert Kompetenzzentrum Wasser Berlin 16/05/2018, POWERSTEP Conference, Munich

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1 YOUR FLUSH, OUR ENERGY FULL SCALE DEMONSTRATION OF ENERGY POSITIVE SEWAGE TREATMENT PLANT CONCEPTS TOWARDS MARKET PENETRATION Rabea-Luisa, Schubert Kompetenzzentrum Wasser Berlin 16/05/2018, POWERSTEP Conference, Munich Funded by the Horizon 2020 Framework Programme of the European Union Grant agreement No

2 Alternative Nitrogen Strategies for small WWTPs

3 Case Study 1: WWTP Westewitz Small WWTP < 5000 PE Inflow < 500 m³/d Biological treated in 2 SBRs (parallel) Sludge is thickened by gravity on site Advanced Nitrogen Control + Nitrogen Removal with Duckweed are tested on site 3

4 Design Parameters WWTP Daily inflow volume Peak inflow volume Water quality parameter Influent Concentrations Influent Loads [m³/d] [m³/h] [mg/l] [kg/d] BOD COD SS TKN TP COD/N = 10:1 Parameter [mg/l] Threshold values for effluent quality for the OEWA Threshold values for effluent quality (AbwVO) BOD 5 [mg/l] <40 <25 COD [mg/l] <70 <110 TN [mg/l] <18 (for T >= 12 C) - TP [mg/l] <8-4

5 WWTP incl. POWERSTEP upgrades 5

6 Advanced Nitrogen Control Advanced primary treatment Low (4:1) COD/N ratio in influent SBR Neccesity of advanced nitrogen control Advanced nitrogen control consisting of: Optimised aeration and feeding regime of the SBRs in standard operation Special mechanisms in case of increased nitrate concentrations in the WWTP effluent 6

7 Depletion based oxygen control Standard operation Advanced control Total aeration time is fixed High oxygen level is always maintained during aeration time Aeration time depeds on oxygen depletion ( c ) and set min. t aeration time (avoiding inhibited nitrification) Oxygen level adjusted between upper and lower set point Less COD oxidation 7

8 Optimised Feeding Regime SBRs are mainly fed during denitrification phase When exceeding the max. drum filter inflow volume Wastewater is directly fed into SBRs (bypass of filtration) 8

9 Special Mechanisms In case of enhanced nitrate concentrations in the SBRs (Sampling point 3) Special mechanisms to temporarily increase COD/N ratio are automatically triggered: 1. Reduction polymer dose 2. Bypass filtration 3. Supernatant withdrawal 4. Acetate dosing 9

10 Advanced Nitrogen Control in Operation Av. COD extraction in primary treatment over a period of 2-3 weeks COD / N ratio influent WWTP (before COD extraction) COD / N ratio influent SBRs (after COD extraction) SBR 1 Av. Denitrification rate SBR 2 Av. Denitrification rate [%] mg NO 3 -N/ (h*g MLVSS) mg NO 3 -N/ (h*g MLVSS) 0 (Reference) Denitrification rates decreased to endogenous level 10

11 Advanced Nitrogen Control in Operation Even at low denitrification rates sufficient denitrification capacity was observed In term of special mechanism for nitrogen removal no acetate dosing, supernatant withdrawal or bypass of filtration was triggered due to insufficient denitrification WWTP is slightly overdesigned: Sufficient denitrification capacity due to reactor volume (low N / DN time) Nitrate concentration effluent WWTP 6 3 Screenshot from PCS 0 POWERSTEP is funded under the European Union Horizon Nitrate 2020 Framework Programme mg/l 11

12 Nitrogen Fractions Effluent SBR 1 Operational issues caused by shortening of aerated times Effluent threshold value: 18 mg/l 12

13 Nitrogen Removal with Duckweed Goals of pilot plant operation: Inoculation Automatization Proof of duckweed concept 13

14 How the Pilot plant was operated Feed to the duckweed reactor => Filtrate from the drum filter Feed (Filtrate) stored in 1m³ IBC over a distribution Treated WW was pumped back to the WWTP Operation of 4 lines (5m² area each) -> 120 L/d (2min/2h) Pump: 5L/min The duckweeds are collected on the sieve 14

15 Results Influent Effluent ph ph: 7,5 8,2 Temp: 12,4 15,1 ph: 7,8 9,5 Temp: 18,8 25,8 ph: 8,1 9,5 Temp: 14,0 20,2 ph: 8,0 8,8 Temp: 8,3 17,0 15

16 Summary and Recommendations Advanced nitrogen control was implemented successfully Stable operation and denitrification achieved for more than one year No exceeding of threshold values due to insufficient denitrification even at high COD extraction (~70%) Aeration control has to be optimised carefully and installation of ammonium probes is recommended Nitrogen removal with duckweed is a promising approach, but the process still needs to be optimised // read more Deliverable 2.1 and

17 Acknowledgement POWERSTEP is an innovation action project supported by the European Union under the Horizon 2020 Framework Programme. Contract no Duration: 1/07/15 30/06/18 17

18 FULL SCALE DEMONSTRATION OF ENERGY POSITIVE SEWAGE TREATMENT PLANT CONCEPTS TOWARDS MARKET PENETRATION Rabea-Luisa Schubert Kompetenzzentrum Wasser Berlin Funded by the Horizon 2020 Framework Programme of the European Union Grant agreement Nr

19 Back up 19

20 Operation Trouble Shooting Planning High COD extraction leading to insufficient denitrification capacity Feeding of SBRs with filtrated wastewater only: Detoriation of settlerablilty anticipated Not expected to that extent Not expected Operation Decrease in denitrification rates observed, but capacity was still sufficient Slight increase in SVI, but no operational issues due to that Depletion based oxygen control with low minimum aeration time leading to inhibited nitrification and an erratic increase in ammonium concentrations Turbidity peaks and blockage of the filter caused by supernatant withdrawal 20