Case Study - Retirement Village

Customer: Engineering Consultancy

Problem

The project is for a 200 plus room capacity complex with a large commercial kitchen located in a basement location (each unit’s sink was not incorporated with grease removal). The client wanted no risk of spillage or odour in the kitchen area which held. 3 x 90L greasy water wash sinks and a large dishwasher.

This requirement negated any under bench system in the kitchen.
The kitchen is in the basement some 3.5m below ground surface and this location also has the risk of liquefaction due to the specified area.

 Design requirements 

  • The kitchen greasy wastewater will need to be collected in a separate basement location

  • The drainage collection point from kitchen is below ground requiring the greasy water to be lifted to the grease trap

  • Pumping grease laden water with a nonspecific pump will emulsify the grease/Fat emulsion reducing the ability of the grease trap to meet its extraction specification.

  • Distance from FOG sources to grease trap may require heat trace and inspection rodding points not located in the kitchen area

  • Distance and flow rate

  • 270L sink capacity@75%=202.5L static Drain time 1 minute-=3.375L/sec = NS 4.0 (normally a MACTRAP 1000L would be used)

  • Sump lift pump type critical to minimize emulsification of greasy water to grease trap.

  • Oversized grease trap needed to further compensate for emulsification - in this case increase static capacity to 1500L 

MACTRAP recommended options 

Install a MACTRAP passive type grease separator externally, presenting two options to overcome the basement services location. 

Option 1.

Locate the grease trap below basement level outside the main building footing and wall. This involves gravity flow to tank and a sump pump to utility line. 

Issue: Due to the depth, 3.5m depth will be required and due to liquefaction risk, it may have to be encased in an engineer designed concrete tomb. 

Option 2

Use a sealable sump and lift pump in a specific location in the basement, separate but close to the kitchen. This will require a pump to lift grey water to a MACTRAP passive trap 1500L with risers and sealed lids. A lift pump specifically designed to avoid emulsification of grease content required. 

Option 3

Install a lift pump as above in the basement floor and pump to a KESSEL freestanding unit such as the sealed “Easy clean” NS4 in the basement storeroom. Using the freestanding auto mix and pump “Easyclean” option, or via vacuum line to outside connection point. With only 3.5mHd the vacuum option would be the more cost effective in this case. 

Option 4

 Install a separate waste filter in the sinks and restrict the sink inflow rate to <.5 to 2.5L/sec then install one of our new self-cleaning under bench automatic grease removal units for each sink to meet the FOG removal requirement. (We have proved with a major international fast food chains that this option is effective). In this instance the option for an under bench was not possible. 

Mactrap recommended solution:

  1. Install Mactraps special KESSEL screw lift pump in separate basement floor area and lift 3.5m . Pump Class S3 (Intermittent) classification EN12050-1 wastewater with possible sewerage
  2. Install MACTRAP CAT D 1500L passive grease trap which can be set to <450mm below ground level. (These can be set deeper with riser extensions). Gravity drain to utility.