Volumetric Wastewater Production and Daily Changes

Wastewater is typically categorized into one of the following groups:

• Domestic wastewater (only produced in households).

• Municipal wastewater (domestic wastewater mixed with effluents from commercial and industrial works, pre-treated or not pre-treated).

• Commercial and industrial wastewater (pre-treated or not pre-treated).

Table 2.1 presents some average data for the Federal Republic of Germany.

Municipal wastewater is composed of 50% domestic wastewater on average. In some cities it may only amount to 25%, in other municipalities nearly 75%. This is of major significance, concerning the additional substances from certain factories which may be either non biodegradable or toxic. Commercial and industrial wastewater are treated together with domestic wastewater and rainwater in communities with a canal system (wastewater and rainwater). In particular, industrial plants with high water consumption have to treat their effluents in their own treatment plants. This is also required of many commercial and some agricultural works. In

Table 2.1 Total wastewater and municipal wastewater (Federal Republic of Germany, 60 million inhabitants, 248534 km2 area; from Popel 1997).

Total wastewater

100%

15.4-109 m3 a-1

694 L (inh. d)-1

Municipal wastewater

32

5.0

230

Industrial wastewater

47

7.2

320

Agricultural wastewater

1

0.2

7

Rainwater drainage in canals

20

3.0

137

Total municipal wastewater

100%

5.0-109 m3 d-1

230 L (inh. d)-1

Domestic wastewater

50

2.5

115

Rainwater

14

0.7

32

Commercial and industrial wastewater

36

1.8

83

an increasing number of growing cities, domestic wastewater and rainwater are collected separately. Although the rainwater is often highly polluted by several organic and inorganic substances (from car washing, car accidents, high tides, etc.), it is mostly discharged untreated into rivers and canals.

Further information about the mean water consumption (= wastewater production) per inhabitant and per day in different European and North American cities is available (Chow et al. 1979; Pöppinghaus et al. 1994; Pöpel 1997). But we must be very careful when comparing these data, because sometimes they are valid only for one city and sometimes the data are valid only for domestic or for municipal wastewater, with or without rainwater. Therefore, we will not discuss these data here.

Within a 24-h period, the flow rate of domestic or municipal wastewater often changes by a factor of 3-4, causing a corresponding change in the flow rate at the treatment plants, because they most often have no storage tanks. Figure 2.1 shows a typical plot of flow rate versus time for a period of 24 h (Schuchardt 2005).

The minimum value during the night and the maximum at midday and evening are typical for many domestic and municipal treatment plants. In larger plants such as Berlin-Waßmannsdorf (~160000 m3 d-1), the profile of flow rate versus time is influenced by the length of the canal system.

The daily and weekly changes in the flow rate are given in Fig. 2.2 (Schuchardt 2005).

Typically, commercial and industrial wastewater flow rates have been published in relation to the mass of specific products (in m3 d-1; Pöppinghaus et al. 1994; Henze et al. 2002). We will not consider these data here; however, see Section 2.4 where relevant regulations are discussed.

Fig. 2.1 Daily change in flow rate at the municipal WWTP Waßmannsdorf, near Berlin, BB 12 (basin 12), Qo from on-line measurements (Schuchardt 2005). Dry weather 6 September 2001; rainy weather 10 September 2001.

Time t

Fig. 2.1 Daily change in flow rate at the municipal WWTP Waßmannsdorf, near Berlin, BB 12 (basin 12), Qo from on-line measurements (Schuchardt 2005). Dry weather 6 September 2001; rainy weather 10 September 2001.

3500

3500

Sep. 17 Sep. 18 Sep. 19 Sep. 20 Sep. 21 Sep. 22 Sep. 23 Sep. 24

Sep. 17 Sep. 18 Sep. 19 Sep. 20 Sep. 21 Sep. 22 Sep. 23 Sep. 24

Mon Tue Wed Thu Fri Sat Sun

Fig. 2.2 Daily and weekly change in flow rate at the municipal WWTP Waßmannsdorf, near Berlin, BB 11 (basin 11), 17-24 September 2001, Q0 from on-line measurements.

0 0

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