FAT SEPARATORS

Application of separators

Fat separators are devices whose task is to retain all particles of animal and vegetable fat. Separators are intended for wastewater treatment wherever the fat content is higher than in domestic wastewater. For example, from restaurants, snack bars, hotels, food processing plants, slaughterhouses and slaughterhouses. The greasy sewage should not be discharged into the sewage system without proper preliminary treatment. Greasy sewage reduces the effectiveness of sewage treatment plants, and causes clogging of sewage pipelines, corrosion of devices and an unpleasant smell. The designed devices should comply with the requirements of PN-EN 1825: 2005 or DIN 4040.

The principle of operation of separators

The operation of the separator is based on the gravity separation of fatty substances that are lighter than water and their accumulation on the surface of wastewater. These devices also act as settling tanks, because during the flow of sewage substances heavier than water (part of the suspensions and solids) fall to the bottom of the tank. Separators are equipped with siphons, thanks to which fatty substances cannot flow out of the device. Wastewater cleaned of fatty substances can be discharged to the general sewage system or individual sewage treatment plant.

Selection of separators

For proper functioning, it is necessary to select the appropriate separator, depending on the amount and nature of the produced sewage. The standards DIN 4040 and PN EN 1825, according to which high-quality fat separators are designed, specify 4 main parameters important during the selection:

• maximum daily wastewater flow,
• sewage temperature,
• fat content in sewage,
• detergent content in sewage.

Correct separator flow rate

NS = Q_s ∙ W_t ∙ W_g ∙ W_d

Table 1. The minimum dimensions of the fat separator based on the calculated nominal value according to PN 1825: 2005

Calculation of the maximum daily flow

  where: 

Q_s - average daily amount of sewage, l/day
Q₁ - average daily amount of sewage, l/s
T - hourly inequality coefficient
t - average installation operation time.

Table 2. Hourly inequality coefficient T for various production and catering facilities.

1 SŻ = processing 1 piece of ox / 2.5 pieces of pig

The average daily amount of sewage should be taken on the basis of actual measurements of water consumption. When it is impossible, then according to the manufacturer's guidelines.

Calculation of the average daily amount of wastewater for mass catering establishments

Q₁ = G ∙ Z_w

Where:

G - number of hot meals prepared in 1 day,
Z_w - water consumption in liters for the preparation of one meal,
Z_w - hotel 80 l,
Z_w – restaurant 50 l,
Z_w – canteen 10 l,
Z_w - hospital 20 l.

Calculation of the average amount of wastewater for meat processing plants

where:

G₁ - daily production of sausage products in kg,
Z_w1 - water consumption in liters per 1 kg of the product

small meat processing plant, up to 5 SŻ / week - 20,
medium meat processing plant, up to 10 SŻ / week - 15,
large meat processing plant, up to 40 SŻ / week - 10,

Installation of separators

Fat separators should be installed as close as possible to the source of technological sewage. Avoid locating them in closed rooms, warehouses and sidewalks with heavy pedestrian traffic. When emptying the separator, an unpleasant smell is emitted, therefore they should not be located near windows and rooms intended for permanent residence of people. Separators should be installed in such a way as to prevent them from freezing. They must be located in places where the service car is easily accessible. These can be devices for external and internal assembly.

The installation of the tanks consists in:

• placing the separator in the trench or on the floor,
• connecting the separator nozzles with the technological sewage pipes,
• backfilling the separator with stabilizing sand if it is a device for external installation,
• setting the top unit on the separator, if any.