Population equivalent

The population equivalent ( pe) is the commonly used in water comparison value for the pollutant loads contained in waste waters. With the help of the residents value can estimate the load of a treatment plant. It corresponds to the sum of the number of inhabitants and population equivalents.

Oxygen demand (BOD)

For the removal of organic contaminants in wastewater oxygen is needed. As a way to determine the pollution levels of wastewater to determine the biochemical oxygen demand in 5 days (BOD5 ) according to a specified procedure.

The resulting daily etc. through showering, bathing, laundry, dishwashing, using the toilet household wastewater of a single inhabitant - about 150 liters a day - caused on average a biochemical oxygen demand of 60 grams per day ( 60 g / d).

Since then, the determination of COD ( with methods of operation ) was always easier and better, the BOD5 has lost its meaning in practice more and more. This was also due to the many possible sources of error in BOD5 determination and the effort and the duration of the study. So there is a COD value after a very short time. (1-3 hr COD / 5 days BOD5)

( Here, there are now methods of operation which is very reliable and very quickly bring meaningful results ). The methods of operation in the years have become very accurate and can keep up with the DIN method with good results.

Since the introduction of rapid analyzes with good success.

This is what Baden- Württemberg since the self-control regulation of 31 March 2001, sewage treatment plants, no routine measurements of BOD5 more ago. Thus, the data density of a catchment area by the CSB is now much higher, more accurate and meaningful. ( Because by now, most sewage treatment plants measure no more BOD5 are hardly more data before ). Prior to the construction of a new wastewater treatment plant, it would be theoretically possible BOD5 measurements for determining the design capacity to allow carry. This will however be in Germany today hardly the case, as we have received a nearly comprehensive wastewater treatment and thus measurement data. But again, then speaks very much for COD determination of load.

Criticism of the COD is with regard to the harmfulness of the method. Why is it always had aspirations to replace the CSB by the TOC, but this ultimately fails always on the practical comparability of TOC values ​​, based eg on EGW.

Also, the materials in COD ( BOD ) are recognized not shown in the TOC, BOD, COD, here are just more practical.

Since the ratio of BOD to COD is pretty much 1 to 2, a PE will now be given with 120 grams per day ( 120 g / d).

Population ( EZ )

As a measure of pollution load, which engages with domestic sewage in a treatment plant serves the population - EZ abbreviated. It corresponds to the number of natural persons, the actual residents who are connected to a sewage treatment plant.

Population equivalent (PE )

As a measure of pollution load, which engages with industrial wastewater in a sewage treatment plant, the population equivalent is used. He compares the pollution load of industrial waste water - for example, the sewage of a brewery, a laundry, a dairy, etc. - with the pollution load in the domestic waste water of a single actual resident. Used to determine the EGW the Biochemical Oxygen Demand (BOD ) is used, divide the average daily pollution load in industrial waste waters of a company by the 60 g / d, which caused an inhabitant.

Example: The waste water an average brewery with a beer output of 100,000 hectoliters per year, equivalent to about 50,000 population equivalent. The same contaminant load is included in the domestic wastewater from a city with 50,000 inhabitants.

To determine the population equivalent value may also have other parameters such as Chemical Oxygen Demand 120g * d ( COD ), nitrogen loads 11g * d, the phosphorus load 1.8 g * d, the cargo organic carbon ( TOC), the suspended load or water consumption 200L e * be used d.

Determination of the population value ( EW)

The sum of the population ( EZ ) and population equivalents ( pe ) gives the population equivalent EW. The following applies: EW = EZ EGW. The unit for the PE, the number of inhabitants and the population equivalent is [E] ( inhabitants).

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