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5.1.1 Decentralized vs. Centralized
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5.1.1 Decentralized vs. Centralized

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As introduced in Section 3.3, wastewater treatment systems are categorized into decentralized and centralized systems. Both alternatives will be assessed, based on the amount of wastewater, effluent discharge standards, as well as local physical and economic conditions. Considering the rapid expansion of urban area, some villages may be located only 3-5km away from urban municipal wastewater treatment plants. Under this circumstance, construction of a sewage system to collect and convey the rural wastewater to existing municipal wastewater treatment plants would be recommended.

 

In China, many villages are composed of different small but densely populated neighborhoods that are separated by agricultural fields or topographic features, such as hills, streams, rivers, highways, or other physical features. In these situations, it may be more feasible to install decentralized systems to serve each neighborhood or cluster of houses instead of installing a large, complex, and expensive collection system. Table 5.1 provides summaries on the different scenarios for the application of decentralized and centralized systems.

 

Table 5.1 Applicability of Decentralized and Centralized Systems

Factor

Decentralized System

Centralized System

Population density

Low density

High density

Topography

Complex

Relatively flat, or suitable for gravity flow

Water consumption

Medium to low consumption

High consumption

Estimated volume of wastewater

Suitable for low volume of wastewater (e.g., less than 50 m3 per day)

Suitable for large volume of wastewater (e.g., over 50 m3 per day)

Capital cost

Relatively low investment on small-scale equipment procurement and installation

Heavy investment on sewer system construction

Operation requirement

Depends on the technologies applied: (i) for passive processes, little intervention is needed; (ii) for advanced technologies, qualified professionals are required.

Need qualified professionals to operate.

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