Decentralized Wastewater Management

Transcription

1 Decentralized Wastewater Management An Overview of Experiences in Mobile, AL Kevin D. White, Ph.D., P.E. University of South Alabama Department of Civil Engineering Mobile, AL,

2 Decentralized Wastewater Management Collection, Treatment, and in-ground reuse NEAR the point of generation. Opportunities for localized reuse Minimizes wastewater: Volumes Infrastructure Costs Facilitates smart growth concepts Enhances property value and livability Integrated into an overall plan of wastewater management (Utility( Managed!)

3 A Smart Sewer System Specifically targeted Effluent sewer Interceptor tanks for solids removal and digestion Small diameter sewer lines (50 mm to 100 mm PE pipe) Low maintenance requirements (minimal biosolids production) Irrigation reuse Potable water replacement Optimizes management Cost effective infrastructure Capital and O&M

4 Fully Utility Managed Construction specs Treatment system operation Long-Term collection and treatment system maintenance, including septage management Billing

5 Traditional Centralized Sewer

6 Traditional Centralized Sewer Characterized by. Long lengths of pipe Large diameter pipes To handle large flows and solids Subject to infiltration and inflow (rain water) Large, complex treatment plants Discharge of effluents to surface waters Extensive redistribution networks (for reuse) Costly $$$$

7 Decentralized Sewer

8 Wastewater Options (and Costs) for Fringe Communities (USEPA, 1997) WW Management Option Total Capital Cost 1995 $ Annual O&M Cost 1995 $ Total Annual Cost 1995 $ Centralized Option 2 km from existing sewer $3,322,900 $83,800 $351,600 Centralized Option 2 km from existing sewer $3,786,900 $83,800 $389,000 Decentralized Cluster $3,783,700 $18,000 $322,900 Centralized Option #1 New gravity collection system connected to existing collection and treatment system (SBR). Centralized Option #2 New gravity collection system connected to existing collection and treatment (SBR). Additional treatment required (upgrade).

9 Mobile, AL 17+ cluster systems in operation Commercial, residential, and schools 40 to 240 kiloliters per day 50 to 300 homes (each system) ~2000 home equivalent (total) Owned and Operated by 3 different public utilities

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11 Cluster System

12 Effluent Sewer (one type of alternative collection) Interceptor tank at each home removes solids (and liquifies) Liquids only are transported in the sewer Small-diameter (50mm to 100mm PE) sewers are the norm Source: Orenco Systems,Inc. Orenco Systems, Inc.

13 Johnson Road Home Buried septic tank & riser

14 Interceptor Tank (Showing Effluent Filter and Pump) Effluent Filter & Pump 4000 L interceptor Tank (to intercept & liquify solids) Orenco Systems, Inc.

15 In-tank effluent filter and pump vault

16 Treatment System Technology (many types available) Highly efficient Small Footprint Low solids production Cost effective Lotus Active-Cell (by Aquapoint) Fluidized, fixed-film reactor

17 Lotus Active-Cell Aerobic Basin and Fluidized Media Bed

18 Treatment Options: Bioclere (by Aquapoint) Fixed-film (trickling filter) process

19 Recirculating Sand Filter RSF Filter Recirculation Tank Schematic Courtesy of Orenco Systems

20 120 kiloliter RECIRCULATION TANK LEVELING OF RECIRCULATION TANKS

21 Residential Development (West Mobile, AL 220+ homes on decentralized sewer) Dauphin Environmental Equipment, LLC

22 Recirculating Sand Filter (Wastewater Treatment)

23 Textile Media Filter Treatment (an inside look)

24 Textile Media Treatment 120 kiloliter per day (each pod 5m x 3m) 17 m 23 m

25 Simple, Textile Media Treatment (120 klpd 175 homes)

26 Control Panel with Telemetry

27 BOD Copeland Island RSF Flow: 6000 to 11,000 gpd 250 BOD, mg/l BODin BODout Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Month

28 Subsurface Drip Irrigation (Small amounts of Treated Effluent Supplied to Plant Roots)

29 Subsurface Drip Reuse Parks

30 Subsurface Drip Reuse Landscaping & Trails

31 Decentralized Sewer Costs Up Front Capital Costs collection system (sewer lines) treatment plant in-ground dispersal or irrigation reuse Tap Fee (when home is connected) ~ $5400/home ~ $3600/home for tank, effluent filter, & pump Total $9000/home (25% to 50% less than traditional centralized sewer) O&M Costs ~ $22/month/home

32 Decentralized Cluster System O&M Costs $20-$24/month per home (actual O&M cost) $35-$40/month per home (sewer fee) Power (20,000 gpd ~90 homes) $70/mo. Weekly/Monthly sampling Upkeep (grass mowing) Personnel (part-time employee 1 day/week) Tank solids management (once every 7 years on average) Pump replacement (every 12 years) 40% utility overhead

33 Utility Management Model Developer Pays utility $500 to $3000 per lot for WWTP Deeds land to utility (WWTP) Installs sewer main in development (2-4 line) (builder/home buyer) pays tap fee ($1800-$3600) $3600) as each house is sold Onsite components (tank, pump, connection, etc.) Developer Utility Builds and operates WWTF Installs and maintains STEP or STEG systems onsite Utility Homeowner Pays a monthly sewer fee ($35-$40/month) $40/month) Homeowner

34 Decentralized Wastewater Management Summary Smaller scale wastewater management Lesser infrastructure and cost Protects public health & the environment Can enhance property values and livability Follows smart growth ideals Integrate into your overall Wastewater Management System Integrate