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Sizing Criteria, Treatment Capacity for Small Wastewater Treatment Systems (Package Plants)

This code of practice was produced by the British Water Packager Sewage Treatment Plant Focus Group.

The Environment Agency, the Environment and Heritage Service (Northern Ireland) and the Scottish Environment Protection Agency support the use of this code of practice, but the Agencies do not specifically endorse any particular manufacturer's product.

The code provides a new table of loadings which allows the total daily load fed into a sewage treatment system to be calculated. These criteria will be widely disseminated and it is recommended that designers of small wastewater treatment systems should use this table of loadings.

The flow and load figures given represent current best practice within the UK but may change with time. British Water welcomes data to improve the content of this document.

Guidance notes are provided to assist the user to consider the nature of the sewage being received for treatment and to identify the various sources of the sewage.

Each manufacturer is aware of the capabilities of their own systems with respect to the individual wastes, but guidance is given so that the user is aware of performance inhibitors.

The table of loadings may be used for all sizes of package sewage treatment plant up to a maximum of 1000 population equivalents.

Use of this table by all UK manufacturers will

The loadings in this code of practice are revised and more comprehensive than previously published guidance (CIRIA PR722001, Environment Agencies PPG4): ammonia figures are includedand loading figures are generally higher.

1 Scope

The purpose of this code of practice is to provide an improved table of loadings to allow the total daily load fed into a system to be calculated. The volume factors given are very similar to those previously published. BOD loading factors have been increased. Ammonia figures are included within the table.

2 Regulations

Early contact / license application with the Regulator to discuss the proposed discharge of sewage effluent is advisable.

3 Definitions of terms
4 Selection Considerations – All applications
Per person / activity / day (unless otherwise specified) FLOW
(Litres)
BOD
(Grams)
Ammonia as N
(Grams)
DOMESTIC DWELLINGS      
Standard residential 200 60 8
Mobile home type caravans with full services 180 75 8
INDUSTRIAL      
Office / Factory without canteen 50 25 5
Office / Factory with canteen 100 38 5
Open industrial site, e.g. construction, quarry, without canteen 60 25 5
*Full-time Day Staff 90 38 5
*Part-time Staff (4 hr shift) 45 25 3
SCHOOLS      
Non-residential with canteen cooking on site 90 38 5
Non-residential without a canteen 50 25 5
Boarding school (i) residents (i) residents 200 75 10
  (ii) day staff (inc. mid-day meal) 90 38 5
HOTELS, PUBS & CLUBS      
Hotel Guests (Prestige hotels) 300 105 12
Hotel Guests (3* & 4* hotels) 250 94 10
Guests (Bedroom only – no meals) 80 50 6
Residential Training/Conference Guest (inclusive all meals) 350 150 15
Non residential Conference Guest 60 25 2.5
Drinkers 12 15 5
Holiday camp chalet resident 227 94 10
Resident Staff 180 75 10
Restaurants - Full Meals - luxury catering 30 38 4
  - Full Meals - pre-prepared catering 25 30 2.5
  - Snack Bars & bar meals 15 19 2.5
  - Function Rooms including buffets 15 19 2.5
  - Fast Food i.e. (roadside restaurants) 12 .12 2.5
  - Fast Food Meal (burger chain and similar) 12 15 4
Students (Accommodation only) 100 56 5
AMENITY SITES      
Toilet Blocks (per use) 10 12 2.5
Toilet (WC) (per use) 10 12 2.5
Toilet (Urinal) (per use) 5 12 2.5
Toilet Blocks in long stay car parks/lorry parks (per use) 10 19 4
Shower (per use) 40 19 2
Golf Club 20 19 5
Local community sports club, e.g. squash, rugby & football 40 25 6
Swimming (where a separate pool exists without an associated sports centre) 10 12 2.5
Health Club/Sports Centre 50 19 4
Tent sites 75 44 8
Caravan Sites - (i) Touring not serviced 100 100 44 8
  (ii) Static not serviced 100 44 8
  (iii) Static fully serviced 180 75 8
HOSPITALS & RESIDENTIAL CARE HOMES      
Residential old people / nursing 350 110 13
Small hospitals 450 140 Assess
Large hospitals Assess individual

 

5 Domestic Housing
6 Commercial Premises
7 Catering premises
8 Hotels & Residential Centres
9 Laundries
10 Toilet Blocks
11 Sports Clubs
12 Golf Clubs
13 Hospitals
14 Caravan Sites
15 Installation
16 Documentation

Records of the loads used to select and recommend the type and size of treatment systems should be maintained by the
specifier and the customer. A typical example follows.

Package Plant Enquiry Sizing Sheet
Our Ref. 123456 Date 10th August 2003 Site ABC Hotel 3* Hotel Client New Architects & Consultants

SOURCE OF WASTE FLOW LITRE / DAY FLOW LITRE / DAY NH3
Description No of Rooms Occupancy No Per Head TOTAL Per Head TOTAL Per Head TOTAL
Rooms 80 2 160 250 40000 94 15040 10 1600
Bar drinkers     120 12 1550 15 1800 5 600
Non resident luxury meals     150 30 4500 38 5700 4 600
Staff, full-time day staff     30 90 2700 38 1140 5 150
Staff, part-time     20 45 900 25 500 3 60
Laundry – all sent off site
Domestic washing machine for tea towels only
        800        
Total load(s)         50340   24180   3010
Effluent Quality Requested     20 mg/l BOD 30 mg/l SS 20 mg/l NH3 N

 

Suggested type of plant: XYZ. Invert: 1.0m. Power: 3-phase. Surface water: all to be excluded from foul sewer.
Consent to discharge: to be obtained from the Regulator. Waste Disposal Units: assumed that none are fitted.
Grease trap: required size “125”.

Notes Swimming pool – present, used for guests only, all backwash wastes to be excluded. No function rooms or catering

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