Sludge ozonation and intermittent aeration through the OSCAR controller: A combined strategy for OPEX minimization in wastewater treatment

Transcription

1 Engineering Conferences International ECI Digital Archives Wastewater and Biosolids Treatment and Reuse: Bridging Modeling and Experimental Studies Proceedings Spring Sludge ozonation and intermittent aeration through the OSCAR controller: A combined strategy for OPEX minimization in wastewater treatment G. Guglielmi Ozono Elettronica Internazionale, giuseppe.guglielmi@etc-eng.it G. Riva Ozono Elettronica Internazionale C. Bancher Ozono Elettronica Internazionale F. Gelmini Ozono Elettronica Internazionale M. Vian Ozono Elettronica Internazionale See next page for additional authors Follow this and additional works at: Part of the Environmental Engineering Commons Recommended Citation G. Guglielmi, G. Riva, C. Bancher, F. Gelmini, M. Vian, and A. Bettinardi, "Sludge ozonation and intermittent aeration through the OSCAR controller: A combined strategy for OPEX minimization in wastewater treatment" in "Wastewater and Biosolids Treatment and Reuse: Bridging Modeling and Experimental Studies", Dr. Domenico Santoro, Trojan Technologies and Western University Eds, ECI Symposium Series, (2014). This Conference Proceeding is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion in Wastewater and Biosolids Treatment and Reuse: Bridging Modeling and Experimental Studies by an authorized administrator of ECI Digital Archives. For more information, please contact franco@bepress.com.

2 Authors G. Guglielmi, G. Riva, C. Bancher, F. Gelmini, M. Vian, and A. Bettinardi This conference proceeding is available at ECI Digital Archives:

3 Sludge ozonation and intermittent aeration through the OSCAR controller: A combined strategy for OPEX minimization in wastewater treatment G. Guglielmi *, G.Riva #, C. Bancher *, F. Gelmini *, M. Vian *, A. Bettinardi # * E.T.C. Engineering srl and E.T.C. Sustainable Solutions srl Via Praga, Trento (TN) - Italy # Ozono Elettronica Internazionale srl, Via Pavia, Muggiò (MB) - Italy info@etc-eng.it Ph: +39 (0) giuseppe.guglielmi@etc-eng.it Ph: Wastewater and Biosolids Treatment and Reuse: Bridging Modeling and Experimental Studies Otranto, June 8 14, 2014

4 Overview of the work OPEX in wastewater treatment: some figures General goal: to achieve operational costs saving in two mid-size extended aeration WWTPs Materials and methods 2 full scale WWTPs The OSCAR controller for N removal and energy saving Ozonolysis for surplus sludge reduction Performance assessment criteria Results: pre-oscar vs post-oscar Conclusions

5 Sludge disposal and energy consumption: how much do they impact on OPEX? Costs for wastewater treatment in Italy: 3.7 billion /y (ca. 0.8% GNP) Energy consumption: Germany: 4.4 billion kwh/y for WWTPs (roughly 0.7% of the overall Germany electricity consumption) UK: 2.3 billion kwh/y USA: 40 billion kwh/y (1% of the overall electricity consumprion in USA) Italy: 3.3 billion kwh/y, kwh/pe/y The sludge «paradox»: about 1% of the volume of treated water does impact for up to 40-50% of the OPEX EU: some 10 MtonDM/y, with severe limitations to disposal in agriculture and landfill Typical Italian figures: Sludge disposal: /tondm Electricity: /kwh

6 Materials and methods The WWTPs WWTP A: Nominal capacity: 50,000 PE 2.7 Mm 3 /y, 3.1 toncod/d 4 identical parallel lanes (overall bio-process volume: 3440 m 3 ) Extended aeration process Discharge in lake Strong seasonal fluctuations due to tourism Specific sludge production: 17.3 kgdm/pe COD /y Specific energy consumption for the bio-process: 88.2 Wh/PE COD /d (32.2 kwh/pe COD /y) Seven single-speed rotatory blowers feeding a main collector then splitted into four WWTP B: Nominal capacity: 30,000 PE 1.3 Mm3/y, 1.75 toncod/y 2 identical parallel lanes (overall bio-process volume: 2000 m 3 ) Extended aeration process Reject water from a poorly performing sludge dryer where dewatered sludge from 20 WWTPs is treated Specific sludge production: 29.1 kgts/pe COD /y Specific energy: 121 Wh/PE COD /d (44.3 kwh/pe COD /y) Two double-speed blowers per lane Basin scale optimization with 24 plants converted to intermittent nitrification/denitrification, where A and B are the largest installations

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8 Materials and methods The OSCAR controller Optimal Solutions for Cost Abatement in nutrients Removal Early developed on 2008, after several demo- and full-scale experimentations at Uni Trento Integrated SCADA and automation controller for real-time monitoring and operation Many SW packages The strenght points: Direct measurement of N forms Multi-level aeration criteria Real-time Fault Detection and Isolation 20 running installations in the range 2, ,000 PE

9 Materials and methods The OSCAR controller Intermittent aeration for single-tank nitrification/denitrification driven by rela-time nitrogen forms measurement Compared to other apporaches (ORP- or ph-based): Higher flexibility in terms of N (and N foms) required effluent quality and energu saving Rough estimation of N concentration in the effluent

10 Power consumprion (kw) Materials and methods - Sludge ozonation Well-proven and long-term established technology which promotes the cryptic growth mechanism O 3 production from air in a containerized scheme 5-8% of the recirculation flow is fed to the contact reactor, where O 3 is dosed to the sludge by means of a pump-venturi-ejector system Nominal O 3 capacity: 2 kgo 3 /h Dosage: 5-16 go 3 /kgtss fed to the contact reactor Overall installed power: 51 kw, including Air compressor: 18.5 kw Dryer: kW Pump/ejector system: 1 kw O 3 destroyer: 2.5 kw O 3 generator: 20 kw Air conditioning: 3 kw Air compressor Molecular sieve Storage tank O3 generator Bioprocess Recycle flow Secondary settling y = x R² = Surplus sludge O3 production rate (kgo3/h)

11 Results Effluent quality h grab samples collected weekly in both influent and effluent streams measurement according to APHA Standard Methods Average TN removal efficiency: from 69.9% up to 85.9% (A), from 67% to 90% (B) WWTP - A Parameter Unit Pre-OSCAR Post-OSCAR COD g m ± ± 2.1 N-N 4 + g m ± ± 1.3 N-NO 2 - g m ± ± 0.3 N-NO 3 - g m ± ± 2.2 TN g m ± ± 2.6 WWTP - B Parameter Unit Pre-OSCAR Post-OSCAR COD g m ± ± 8.6 N-N 4 + g m ± ± 0.6 N-NO 2 - g m ± ± 0.06 N-NO 3 - g m ± ± 1.1 TN g m ± ± 1.6

12 May-12 Jun-12 Jul-12 Aug-12 Sep-12 Oct-12 Results Energy saving Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 May-12 Jun-12 Jul-12 Aug-12 Sep-12 Oct-12 Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 WWTP A and WWTP B Parameter Unit Pre-OSCAR Post-OSCAR A: Energy consumption for kwh y ,743 1,059,384 bioprocess A: Specific energy consumption for bioprocess kwh PE COD -1 y (-25.1%) B: Energy consumption for kwh y , ,232 bioprocess B: Specific energy consumption for bioprocess kwh PE COD -1 y (-14.6%) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% -50.0% -60.0% -70.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% -50.0% -60.0%

13 May-12 Jun-12 Jul-12 Aug-12 Results Sludge production Sep-12 Oct-12 Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 May-12 Jun-12 Jul-12 Aug-12 Sep-12 Oct-12 Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 WWTP A and WWTP B Parameter Unit Pre-OSCAR Post-OSCAR A: Sludge production tondm y A: Specific sludge production kgdm PE -1 COD y (-35.8%) B: Sludge production tondm y B: Specific sludge production kgdm PE -1 COD y (-35.8% ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% -50.0% -60.0% -70.0% 0.0% -10.0% -20.0% -30.0% -40.0% -50.0% -60.0% -70.0% -80.0%

14 Results Impact on OPEX WWTP - A WWTP - B HW+SW ,00 Mixer + probes ,00 Electrical equipment ,00 Ozone ,00 Total CAPEX ,00 Energy saved kwh/y Cost per kwh 0,15 /kwh Money saved for energy /y Sludge not produced 185 tondm/y Cost per ton of DM 500 /tondm Money saved for sludge disposal /y Extra costs for maintenance /y Energy consumption for ozonation kwh/y Cost for O3 energy /y Net saving /y Pay-back time 5.4 y HW+SW ,00 Mixer + probes ,00 Electrical equipment ,00 Ozone ,00 Total CAPEX ,00 Energy saved kwh/y Cost per kwh 0,15 /kwh Money saved for energy /y Sludge not produced 171 tondm/y Cost per ton of DM 500 /tondm Money saved for sludge disposal /y Extra costs for maintenance /y Energy consumption for ozonation kwh/y Cost for O3 energy /y Net saving /y Pay-back time 7.0 y The overall net benefit results in a actual shorter pay-back time due to intermittent aeration process installed also in smaller WWTPs

15 Conclusions The OSCAR controller was successfully coupled with sludge ozonation process in two mid-scale WWTPs Improved nitrogen removal efficiency was observed in both cases The energy consumption for the bio-process was cut of 15 to 25% Sludge production was reduced of some 35% Single-installation pay-back time: 5.4 and 7 years, but a shorter return on investment can be achieved on a basin-scale application of the OSCAR Still to be clarified the actual effect of intermittent aeration on sludge reduction (in extremely under-loaded WWTP Y obs dropped down of some 26%) Further optimization by synchronizing anoxic phases with sludge ozonation

16 In memoriam of Dr. Giancarlo Riva CEO and founder of OEI, great expert in O 3 technologies. And friend