Introduction to decentralized wastewater management systems

This chapter will

• Introduce the subject and importance of decentralized wastewater management systems;

• Introduce the purpose, need and audience for this manual; and

• Present the terms and definitions common to these systems.

About Figure 1.1

The photos of Mr. Makara's latrine factory near Phnom Phen, Cambodia (Figure 1.1), illustrate how the power of markets can be used to scale up sanitation. Market-based sanitation means matching the ability to supply products with programs that enhance demand and provide incentives fostered by engaged local governments. The major components are:

(1) Demand generation: People are generally willing to pay for improved sanitation if they believe it will address their needs, wants, and desires. Understanding what these may be for a population means information must be gathered. Development specialists use tools such as customer surveys, focus group discussions, and interviews with key stakeholders to find out what people really want, what they think, and what they think they need related to sanitation. In some instances, their overriding desire is to improve the health of their children. In other areas, it might be the convenience of having indoor plumbing or the status of having a flush toilet. When sanitation technologies are promoted to address the needs, wants, and desires of people treated as customers, they will be more willing to pay for services. Also, it is important to note that to achieve sustainability, the sanitation improvement must fulfill the promises that are made, or people will find other uses for their money.

(2) The sanitation value chain: The value chain of decentralized wastewater management describes how technologies are manufactured, sold, delivered, installed, operated, and maintained. To sustain the value chain, products should be manufactured using local materials and labor, and service providers should be trained through strong capacity-building exercises. When demand is generated (as described above), the value chain produces sales, profits, jobs, and economic development.

(3) The enabling environment: This is the combination of incentives and the regulatory framework that promotes rather than inhibits participation in sanitation improvement programs. Good programs include incentives that offer tangible benefits to those that comply, as well as enforcement provisions for those that do not. It is also the way local governments interact with citizens and businesses. Frameworks that speed up and simplify a fair and transparent regulatory process can be powerful tools local governments can use to scale up sanitation using decentralized wastewater management.

Achieving sanitation improvements at scale requires evidence-based promotions campaigns, a robust value chain, and an enabling environment that works. When all three of these elements are present together, improving sanitation can be a strong force for major social and environmental change.

1.1 BACKGROUND

In the past several decades, many organizations have described the lack of basic sanitation for much of the world's population. Estimates put the number of unserved people at more than two billion, mostly in South and East Asia and sub-Saharan Africa. In those regions there are 45 countries where sanitation coverage is less than 50% (Figure 1.2).

While the estimates and definitions of access to basic (often referred to as 'improved') sanitation have been challenged, it is widely agreed that this problem represents a crisis given the strength of the link between poor sanitation and disease and death, especially in children. Poor sanitation results in a significant yet preventable health and financial burden on individuals, families, communities, and countries. The economic burden is quite significant. For example, in India it was estimated that in 2006 the cost of poor sanitation amounted to 6.4 percent of the country's gross domestic product (World Bank Water and Sanitation Program, 2010).

To meet the widespread need for wastewater treatment, centralized sewerage systems have been implemented as the norm for large, medium, and even small sized cities and municipalities in developed countries. However, it is unlikely that centralized wastewater treatment systems will be used in developing country settings except in the most densely populated urban centers.

The rest of the population, as well as the commercial, industrial, public, and other facilities lacking proper sanitation systems will need to rely on site-specific solutions using on-site and decentralized wastewater treatment, dispersal, and reuse technologies. The benefits of smaller, decentralized wastewater management systems are many, as they use simpler technologies, allow for more cost-effective reuse of treated effluent on or near the site where the wastewater was generated, are generally simpler to install and maintain, and can be a force for economic development. Indeed, they not only improve sanitation and environmental health, but they can also lead to job creation along the entire value chain, from equipment manufacturers to system designers, installers, and operators.

1.1.1 Combining Technologies to Form Systems

Decentralized wastewater management systems, like their centralized counterparts, use a variety of technologies that work together to achieve many goals. The major goals are to remove sewage away from humans, reduce the pollution from the collected wastewater, and safely disperse the treated effluent, or reuse it and other residuals for beneficial purposes. These are accomplished by linking appropriate technologies together to form systems that meet the specific needs of the end-users. These systems, which vary widely in both complexity and cost, can include:

• toilets, or the human interface that includes individual toilets, latrines, and community-based toilet blocks that serve as the first point of collection for human waste and help to remove it from potential human contact;

• sewers and wastewater collection technologies that collect wastewater from the interface and deliver it to locations for treatment;

• treatment technologies that treat wastewater to a level that is 'safe' for discharge, reuse, or dispersal; and

• reuse and recycling, which represent the technologies that allow for the safe reuse or recycling of the treated effluent or other residuals from the wastewater treatment process, such as biosolids and biogas.

Selecting the most appropriate technologies requires knowledge of the wastewater source and an understanding of...