Municipal Industrial Pretreatment Program Development from Why to How. Barbara L. Swafford, P.E. Gerken Swafford Engineering Solutions, LLC

Transcription

1 Municipal Industrial Pretreatment Program Development from Why to How Barbara L. Swafford, P.E. Gerken Swafford Engineering Solutions, LLC

2 Why Pretreatment Programs Types of Industrial Limitations Basis for Local Limit Development Determination of Allowable Headworks Loadings Calculation of Total Allowable Industrial Load Allocation of Total Allowable Industrial Load to Industries Presentation Overview

3 to regulate the introduction of pollutants from nondomestic sources into Publicly- Owned Treatment Works (POTWs) Purpose of Pretreatment Programs

4 Early 1980 s started becoming a requirement Some resistance to the program A Little History

5 Wastewater Treatment Plants And. Collection Systems POTWs

6 Categorical Standards Technology based standards setting industry-specific effluent limits Standard Types

7 General and Specific Prohibitions Apply to any user of the POTW Typically included in pretreatment ordinance Includes protection of collection systems Standard Types

8 Local Limits - Developed specific to each POTW to protect: Water quality Biosolids quality Treatment Plant processes from inhibition Standard Types

9 Water quality based Generally provided in NPDES permits as either A specific effluent limitation Or as waste load allocation values Local Limits

10 Sludge quality based Dependent on ultimate disposal method Part 503 Standards for the use or disposal of sewage sludge Local Limits

11 Inhibition of Biological Wastewater Treatment Processes Activated sludge Trickling filters Nitrification Anaerobic Digestion U.S.EPA Guidance Manual Local Limits

12 WWTP Headworks Primary Treatment Activated Sludge Tertiary Treatment Sludge Treatment Final Disposal Discharge to Receiving Stream Removal Efficiencies

13 Through Primary Treatment Activated Sludge Inhibition Through Activated Sludge Tertiary Treatment Inhibition Whole Plant Removal Water quality based criteria Sludge disposal criteria Removal Efficiencies

14 In-plant Sampling Recommended Whole plant removal from operating records Special sampling for primary, activated sludge, etc. removals Analysis should be as low as you can go U.S.EPA Guidance Manual Removal Efficiencies

15 Calculated based on appropriate criteria and removal efficiency. Allowable Headworks Loadings

16 Based on Water Quality Criteria AHL = (8.34)x(Cnpdes)x(Qwwtp) (1-Rwwtp) Where: AHL = Allowable headworks loading (lbs/day) Cnpdes = Water quality criteria (mg/l) Qwwtp = WWTP average flow rate Rwwtp = Removal rate across WWTP as decimal 8.34 = Unit conversion (lbs/gal) Allowable Headworks Loading

17 Based on Sludge Quality Criteria AHL = (8.34)x(Csldg)x(PS/100)x(Qsldg)x(Gsldg) Rwwtp Where: AHL = Allowable headworks loading (lbs/day) Csldg = Sludge quality criteria (mg/kg dry) Qsldg = Sludge flow to disposal (mgd) Rwwtp = Removal rate across WWTP as decimal PS = Percent solids of sludge to disposal Gsldg = Specific gravity of sludge (kg/l) 8.34 = Unit conversion (lbs/gal) Allowable Headworks Loading

18 Qsldg (mgd) = (dry tons/day / %solids) x 2,000 lbs mg x kg x 8.34 lb x 1 gal = 1 mg kg 2.2 lb 1 gal 3.79 l l Specific gravity generally assumed to be 1 kg/l Sludge Calculations

19 Based on Inhibition Criteria AHL = (8.34)x(Cinhib)x(Qwwtp) Rproc Where: AHL = Allowable headworks loading (lbs/day) Cinhib = Inhibition criteria (mg/l) Qwwtp = WWTP flow (mgd) Rproc = Removal rate through process as decimal 8.34 = Unit conversion (lbs/gal) Allowable Headworks Loading

20 Calculate allowable headworks loadings for all criteria and pollutants of concern Summarize all in a table Identify the most restrictive or the maximum allowable headworks loading (MAHL) Most restrictive will be used to calculate total allowable industrial discharge Allowable Headworks Loading

21 Residential and Commercial Industrial Safety and Growth Factors Allowable Headworks Loading Allowable Industrial Loading

22 Residential and Commercial Contribution Concentrations determined by in-system sampling Flow determined by subtracting industrial flow from total WWTP flow Loadings determined by: lbs/day = 8.34 x conc. (mg/l) x flow (mgd) Allowable Industrial Loading

23 Maximum Allowable Industrial Loading MAHL Safety Factor Res./Comm. Allowable Industrial Loading

24 Uniform Concentration Uniform concentration for all industries Uniform concentration for only industries discharge pollutant of concern Mass Allocation Used when one or two industries discharge a majority of pollutant More involved calculation Allocation Options

25 Cind = Lall 8.34 x Qind Where: Cind = Concentration limit (mg/l) Lall = Maximum allowable industrial load (lbs/day) Qind = Industrial contributory flow (mgd) 8.34 = Unit conversion (lbs/gal) Uniform Concentration

26 Determine Total industrial loading from all industries (lcurr(t)) Current loading from specific industrial user (lcurr(x)) Calculate percentage (%curr(x)) lcurr(x)/lcurr(t) = %curr(x) Mass Allocation

27 Apply percentage to total allowable industrial load (Lall) to determine specific industrial allowable load (Llim(x)) Lall x %curr(x) = Llim(x) And convert to concentration Clim(x) = Llim(x) 8.34 x Q(x) Mass Allocation

28 Surcharge Programs Oil & Grease Programs Best Management Practices Miscellaneous Discussions

29 Questions?