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<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

7.1.2 Characteristics

It can be assumed that there is little difference in total loading discharged between EU15 (European Union Member States) and the AC10. However, the use of water per capita is considerably higher in AC10, while the quality of rain water that has to be treated is often lower because of the presence of separated sewers (e.g. Poland). Table 7.4 compares quantity (flow) and quality (concentration) of wastewater from EU 15 and AC 10 (ETC/IW, 1998). It is supposed, that the current lower wastewater concentrations in the AC 10 compared to the EU 15, which originated in the economic regression, will increase in the coming years through industrial and agricultural growth. Future treatment capacities in the AC 10 will not completely cope with increasing wastewater quantity and declining quality until the UWWTD and other directives are in full power.

In the early 1990s, the total organic pollution load from urban wastewater treatment plants for the AC 10 was for BOD5 about 1136 kilotonnes O2/year. The nutrient load was at the same time for total P about 69 ktonnes P/year and for total N about 334 ktonnes N/year (ETC/IW, 1998). There is little information available regarding the other transition countries.

In the European CIS countries a high percentage of the population is connected to municipal wastewater treatment plants (60-75%), but most villages discharge without treatment. Municipal wastewater treatment plants are mostly designed to reach a 60-70% reduction in BOD. However, in the early 1990s only about 60% of the installations were functioning and there is no indication that the situation has improved since then.

Table 7.4: Wastewater characteristics in the EU 15 and AC 10 countries

Parameter EU 15 AC 10
Quantity (l/c/d)
Dry weather flow 117 180
Rain water discharge 43 20
Total quantity 184 200
Quantity (mg/l)
COD 523 350
BOD5 191 100
N (Kjeldahl) 48 35
P tot 8 6
Suspended matter 304 117
Source: (ETC/IW, 1998)

Sometimes, the pollution discharge standards of municipal wastewater are ignored. This is due to the limited treatment capacity of most plants, causing overload, and the high pollution load of the incoming wastewater. Due to poor maintenance and the poor technical state of installations, overloading and even complete breakdown, the reconstruction or extension of existing plants is unsatisfactory or has been completely abandoned for the time being.

Many industrial enterprises are connected to municipal treatment plants and most of them are required to have pre-treatment facilities. However, industrial wastewater plants that were constructed in past years are either not in use or not well maintained. The absence of detoxifying pre-treatment of wastewater from i.e. metal finishing / galvanising enterprises leads to an excess of heavy metals in municipal treatment plants, undermining biological treatment. It is assumed, that the situation has not greatly improved over the last few years, although the continuing recession accounts for some reduction in industrial wastewater generation. Furthermore, treatment efficiency and other investment–dependent indicators have also deteriorated further.

In Croatia, the bulk of generated wastewater is treated only mechanically (primary treatment) (81%); which means poor performance yields, except for suspended solids, and a poor effect on dissolved pollution. About 6% is biologically treated and 13% are combined treated. There are no data available for the pollution load, despite existing monitoring systems. The reduction in pollution load is estimated at around 25% of what is treated. Since wastewater treatment has been a priority for the past several years, many municipalities have built treatment facilities, but their operation is fraught with difficulties. Most municipalities which borrowed to finance 50% of the building costs, cannot cover the loans and so cannot operate and maintain the plants properly. The result is often, that they bypass their empty facilities and discharge their wastewater untreated. At the same time, new projects are designed and partly financed by the national water agency to equip urban settlements (EPR, 1999).

 

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