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CHAPTER 6. TECHNOLOGICAL AND MANAGERIAL ASPECTS OF EUTROPHICATION

6.1. Introduction

This chapter focuses on methods available to solve the problems related to eutrophication of lakes and reservoirs, which are discussed in different chapters of this publication. The problems may be divided into the following four groups:

1. How to solve the problems associated with wastewater?
2. How to solve the problems associated with non-point (diffuse) pollution?
3. How to solve the problems associated with wastewater sludge and domestic garbage?
4. Can land use control be applied to solve the problems and how?

This chapter discusses the possibilities to answer these questions and outlines possible solutions to a number of concrete problems defined by specific pollutants. The discussion is based on the holistic aspects of environmental management, which implies that a proper solution must consider an answer to all the above four questions and must solve them simultaneously.

A review of different methods to solve the problems is presented. However, detail information is mainly provided for the "soft" technological and most cost-moderate methods, which are directly applicable to developing countries. In addition, the "soft" technologies require more labour and more land and therefore may be a considerably better solution than advanced technological methods. Advanced wastewater treatment with four-treatment steps, including nitrification and denitrification, is very expensive and also difficult to operate.

General recommendations on which methods should be applied to which problems, and under which context, cannot be given, because the problems are too complex and affect very complex systems, particularly different ecosystems. It is, however, possible to give guidelines on how to select a good solution to a specific environmental problem. The guidelines given in this chapter also include several decision-making trees with reference to tables to facilitate the selection process.

The approximate investment cost and running cost is mentioned for all solutions. It is not possible to give accurate cost statements, as the cost depends on local conditions.

The possibility to address the problem at the source by separation of different wastewater types by application of an alternative sanitation system are presented. This should not be considered as a complete solution to the pollution problem but an additional possibility to find a more ecologically sound solution by using the separation, which can be carried out in combination with proper selected treatment methods.

Thirty years ago, the so called diffuse or non-point sources of pollution did not play any role in the green debate. Meanwhile, particularly in the late seventies and the early eighties, it became recognized that the diffuse and internal sources, such as lake sediments, are often more critical sources of pollution than the point sources. The point sources can be in many cases significantly reduced by easily manageable end-of-pipe techniques. This development has provoked new types of techniques, denoted ecotechnology, which enables better control of the diffuse pollution sources. It encompasses the application of waste stabilization ponds, constructed wetlands, and other technologies often denoted as "soft" technology, and also includes proper planning of the land use from an ecological point. Techniques based on ecotechnology are able to solve both wastewater problems and diffuse pollution problems. As these techniques are relatively cost-moderate, effective, and easy to operate, they are discussed in detail in this chapter.

From the above introduction, several important recommendations may be derived. They are touched upon throughout the chapter and may be summarized by the following points:

• Expect that a proper environmental strategy will require a wide spectrum of approaches and techniques. However, the selection process is difficult.
• Expect that proper environmental management will require the application of a combination of several technologies.
• The correct timing of the proper steps in environmental management is extremely important. It is therefore recommended to set up a complete environmental management plan at a very early stage to be able to use the available resources as close to the optimum as possible.
• It is often extremely beneficial, particularly from an economic point of view, to consider prevention instead of correction, as it is often extremely costly to perform ecosystem restoration.
• Due to the complexity of the system and the problem, proper ecological knowledge of the ecosystem is a prerequisite for an ecologically sound environmental management. This is the only known method to avoid unexpected reactions of the specific ecosystem.
• As all ecosystems are open systems, an optimum solution can only be found if the entire watershed area is considered. This is further discussed in Section 6.8. in this chapter.

Four sections of this chapter (i.e., Sections 6.3. to 6.7.) are devoted to the discussion of the possible solutions to wastewater problems, as wastewater is causing the most important problems of lakes and reservoirs. A general overview is given in the first of these four sections. A detailed discussion of waste stabilization ponds and wetlands is given in the next two sections, and, finally, the selection of a proper solution is discussed in Section 6.7.

The discussion of the solution to solid waste problems with concrete recommendations takes place in Section 6.8. and the general considerations to land use control is also given in Section 6.8. The rest of the twelve sections in the chapter contain a review of sediment remediation methods, a description of monitoring of water quality and eutrophication programmes, and a discussion of methods for the restoration of lakes and reservoirs.

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