Passive, Two-stage Nitrogen Reduction Systems for Onsite Wastewater Treatment

Transcription

1 University of Florida Water Institute Symposium February 15-16, 2012 Passive, Two-stage Nitrogen Reduction Systems for Onsite Wastewater Treatment by Damann L. Anderson, P.E. 1 1

2 Acknowledgements Many thanks to colleagues on this work: Josefin Edeback Hirst, P.E., Hazen and Sawyer Daniel Smith, Ph.D., Applied Environmental Technology Eberhard Roeder, Ph.D., Florida Dept. of Health Elke Ursin, Envir. Health Program Consultant, Florida Dept. of Health UF Gulf Coast Research and Education Center, Hillsborough County, Florida Craig Stanley, Ph.D. Gurpal Toor, Ph.D. 2

3 Presentation Outline Onsite Wastewater Nitrogen Reduction Passive Nitrogen Reduction Systems Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Project Background Pilot Scale Results What s Next? Questions and Answers 3

4 Onsite Wastewater Nitrogen Reduction Overview 4

5 Conventional onsite sewage treatment and disposal systems (OSTDS) 5

6 Bio-N removal is a two-stage process 1. nitrify nitrogen compounds to NO 3 (nitrification) 2. denitrify NO 3 to nitrogen gas (denitrification) Organic N NH 4 + NO 2 - NO 3 - N 2 Ammonification Nitrification (Aerobic) Denitrification (Anoxic) 6

7 Two types of denitrification reactions Denitrification: reduction of nitrate to N 2 gas: Heterotrophic NO CH 3 OH H C 5 H 7 O 2 N N H CO 2 Autotrophic NO S o CO H 2 O C 5 H 7 O 2 N + SO N 2 + H + 7

8 What are passive onsite nitrogen reduction systems? Current N-removing onsite systems are mechanical treatment units Passive Nitrogen reducing OSTDS that are more similar to conventional onsite systems in their operation and maintenance Passive nitrogen removal systems achieve TN concentrations of <10 mg/l using a reactive media for denitrification, and 1 pump, if necessary 8

9 Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Study 9

10 FOSNRS project initiated by Florida legislature Laws of Florida, , FDOH study to further develop passive & cost-effective nitrogen reduction strategies for OSTDS Florida Onsite Sewage Nitrogen Reduction Strategies (FOSNRS) Project began in 2009 This presentation focuses on preliminary project results from selected two-stage passive biofiltration systems. 10

11 Presentation today focuses on sulphurbased denitrification systems Previous Studies of Sulphur-based Denitrification Reference Denitrification Media Results Kanter, Tyler and Converse (1998) Sengupta and Ergas (2006) Brighton (2007) Smith et al. (2008) Sulphur/Dolomite Sulphur: <2.5 mm Sulphur/Oyster Shell (75/25% by volume) Sulphur: 4.7 mm Sulphur/Oyster Shell (75/25% by volume) Sulphur: 2-5 mm Sulphur/Oyster Shell (75/25% by volume) Sulphur: 2-5 mm TN Removal: 87.9% Nitrified Influent: 23.5 mg-n/l Effluent: 3.0 mg-n/l NO 3 -N Removal: 80% Influent: 2-32 mg NO 3 -N/L Effluent: 4.2 mg NO 3 -N/L TN Removal: 81.7% Nitrified Influent: 23 mg-n/l Effluent: 4.2 mg-n/l TN Removal: 93.8% Nitrified Influent: 35.2 mg-n/l Effluent: 2.2 mg-n/l 11

12 Pilot study to further the concepts developed by Smith, et. al (2008) Objectives: Follow up to previous study with larger, pilot scale units and various media combinations Develop detailed performance data for passive biofiltration designs Produce scalable design criteria from pilot scale biofilters for subsequent full-scale testing 12

13 A unique pilot facility was constructed at UF research center University of Florida, Institute for Food & Agricultural Sciences (IFAS) 475 acres of land in SE Hillsborough County Facility conducts agricultural research & trials for vegetables, fruit and ornamental plants Experts in soil and water science onsite Source: 13

14 Test facility includes numerous treatment trains All use two-stage biofilters: Stage 1 Nitrification Stage 2 Denitrification Stage 1 unsaturated filters 2 media layers evaluated 15 and 30 media depths Evaluated single pass vs recirculating stage 1 biofilters Evaluation of both lignocellulosic and sulphur denitrification biofilters Also testing reactive media in a more in-situ/in-ground system approach 14

15 Test facility construction Setting up tanks Mixing Media Batches Gravel Underdrain 15

16 Various nitrification media are being studied Examples of Stage 1 Media Zeo-Pure clinoptilolite Expanded polystyrene 16 Filter sand Expanded clay

17 Various denitrification media are being studied Examples of Stage 2 Media Lignocellulosics Expanded Clay Elemental Sulphur 17

18 Two stage single pass biofilters 18

19 Two-stage single pass biofilters Stage 1 Unsaturated Biofilters - Nitrification Stage 2 Saturated Upflow Biofilters - Denitrification 19

20 We are also evaluating Stage 1 recirculating biofilters 20

21 Stage 1 recirculating biofilters & Stage 2 horizontal saturated biofilters Stage 2 Saturated Biofilters Stage 1 Recirculating Biofilters 21

22 Pilot Scale Results 22

23 Results show consistent treatment at very low N levels Stage 1 Treatment Media Stage 2 Treatment Media Effluent TN 1 (mg N/L) TN Reduction (%) MEAN STE STD DEV MIN MAX MEAN 2.60 Single Pass Clinoptilolite Sulphur STD DEV 0.52 MIN MAX 3.02 MEAN 2.54 Recirculation Clinoptilolite Sulphur STD DEV 0.40 MIN MAX Continuous operation for 367 days 23

24 TN Reduction Efficiency, % Results of sulphur based denite systems are excellent 100% 90% 80% 70% 60% 50% 40% 30% Both Systems: Stage 1 Nitrification: Clinoptilolite Biofilter Stage 2 Denitrification: Sulphur Biofilter 20% 10% Single Pass System Recirculating System 24 0% Experimental Day

25 Single Pass System Stage 1 Nitrification: Clinoptilolite Biofilter Stage 2 Denitrification: Sulphur Biofilter 25

26 Recirculating System Stage 1 Nitrification: Clinoptilolite Biofilter Stage 2 Denitrification: Sulphur Biofilter 26

27 Sulfate, mg/l TKN or NOX-N, mg/l Single pass vs recirculating biofilters: sulfate 500 Influent Single Pass Recirculating Sulfate TKN NOx-N STE Stage 1 Stage 2 Stage 1 Stage 2 0

28 Total Nitrogen, mg N/L Comparison with other N-reduction studies Mechanical Systems PBTS - Wakulla County Florida Keys OWNRS La Pine Study La Pine - Nitrex Single Pass - PNRS II Recirculating - PNRS II Results are Mean +/- SD Passive Biofilter Systems 28 0

29 Next Steps 29

30 Install full-scale systems at actual home sites Passive Nitrogen Systems Pumped Flow 30

31 If topography allows, we will try gravity systems Passive Nitrogen Systems Gravity Flow 31

32 Successful results from FOSNRS Study would provide: OSTDS designs that achieve nutrient removal similar to wastewater treatment plants Passive systems that are effective and user-friendly for property owners Nitrogen reduction from OSTDS in sensitive watersheds where municipal sewers are not feasible 32

33 Questions? 33