257 C.M.R. 2.13 – Classification of Wastewater Treatment Facilities

(1) Each municipal wastewater treatment facility shall be classified by the Board as either 1M, 2M, 3M, 4M or 5, 6, or 7 for large or complex facilities. Each industrial wastewater treatment facility shall be classified as either 1I, 2I, 3I, 4I, or 5, 6, or 7 for large or complex facilities. The increasing numerical class indicates increasing complexity of operation and a higher level of training, knowledge, and experience required for operation.
(2) The class of a facility shall be established by adding together all rating values reflecting the complexity of operation for units which are present in the facility, as set forth below:
Rating Values for Classification of Facilities
Unit Rating
Aeration; mechanical or diffused air greater than 0.5 MGD 10 less than 0.5 MGD 6 Aeration; sludge, re-aeration 3 Aeration; pure oxygen greater than 0.5 MGD 10
BOD Removal 1 and up*
Carbon Filter 2-5 Carbon absorption in an Industrial facility 5 Carbon reactivation 10 Centrifuge 8
Chemical addition 2 points per
chemical
Chlorination pre, gas or liquid 2 Chlorination post, gas or liquid 2-5 Clarifier, tube settling or inclined plate 2-5 Clariflocculation 6 Coagulation and Neutralization 5 Comminution 1 Condenser 2 Cooling Tower 1-3
Dechlorination 2 Denitrification 5 Dissolved Air Flotation 5
Electrodialysis 5 Electrolytic Recovery 5
Unit Rating
Equalization 2 Evaporators 2-5 Extended Aeration greater than 0.1 MGD, less than 0.5 MGD 6 Extended Aeration equal to or less than 0.1 MGD 4
Flash Mixing 1 Flow measurement 1 Flocculation 1
Grit Chamber, Aerated 2 Grit Chamber manually cleaned 1 Grit Chamber mechanical grit removal 2
Heat Exchangers 2 High rate filtration units less than 0.1 MGD 1 greater than 0.1 less than 0.5 MGD 2 greater than 0.5 less than 1.0 MGD 3 greater than 1.0 MGD 4 Hypochlorite generation 5 Hypochlorination pre and/or post 1 Hydrocyclones (grit removal) 3
Imhoff tanks 3 Incineration 10 Instrumentation 1-5 Ion Exchange 2-5
Laboratory 1-3 Land Irrigation, spraying 2 Land Irrigation, direct discharge 2
Membrane Filtration 3-5
Nitrification 10
Odor Control 2-5 Oil Separation 2 Oxidation Ditch 5 Oxygen Generation 10 Ozonation 5
Polishing Filter 2 Post-aeration (cascade) 1 Post-aeration (mechanical) 2 Pre-aeration 1 Primary Settling; airlift or manual sludge removal 3 Primary Settling; mechanical sludge removal 5 Primary sludge holding and mixing 2 Pumping (in plant) 3 Pumping stations under operator's control 1
Reaction Vessel 3 Reverse osmosis 5 Rotating Biological Contactors 4
Unit Rating
Rotating Biological Contactors; multiple stage 7 Rotary Drum Dryers 5
Sand filters; multi media, automatic backwash 3-4 Sand filters; intermittent 2 Sand filters; polishing 1 Sand filters; subsurface 1 Screens (mechanical) 1 Scum Concentrator 2 Secondary settling; airlift or manual sludge removal 3 Secondary settling; mechanical sludge removal 5 Septage facilities 2-5 Sludge blending 2 Sludge composting 2-5 Sludge drying beds 2 Sludge digestion; aerobic 4 Sludge digestion; heated and mixed anaerobic 10 Sludge digestion; heated and unmixed, anaerobic 8 Sludge digestion; unheated 2 Sludge elutriation 3 Sludge incinerators 10 Sludge press; belt 8 Sludge press; plate and frame 2-8 Sludge storage 2 Sludge thickeners; gravity 5 Sludge thickeners; flotation 5 Stabilization ponds; non-aerated 1 Stabilization ponds; aerated 3 Stripping Air 2-5 Steam 2-5
Trickling filters; high rate 4 Trickling filters; staged 4 Trickling filters; standard rate 2
Ultraviolet disinfection 2-5
Vacuum filter 10
Wet Air Oxidation 10
Design BOD in Pounds/Day x "f" * BOD Removal Rating = 1000
"f" = 0.3 for primary treatment and 0.8 for secondary or higher facilities.
(3) Wastewater treatment facilities shall be classified according to the following cumulative rating value:
Class Cumulative Rating Value
Class 1 (M or I) 1-7 Class 2 (M or I) 8-20 Class 3 (M or I) 21-30 Class 4 (M or I) 31-50 Class 5 (C) 51-65 Class 6 (C) 66-80 Class 7 (C) 81 or more
(4) Class 1 (I) and Class 2 (I) facilities which have fewer than three units or a rating of 20 or fewer points shall be considered Type I facilities for the purposes of 310 CMR 4.00.
(5) Class 1 (I) and Class 2 (I) facilities with greater than three units or a rating of more than 20 points and Class 3 (I), Class 4 (I), Class 5, Class 6, and Class 7 facilities shall be considered Type II facilities for the purposes of 310 CMR 4.00.
(6) The Board may establish a rating value for any unit not shown on the table. The Board may change the classification of a particular wastewater treatment facility when there are site-specific factors affecting the complexity of the treatment process.