Wastewater reclamation through a combination of natural systems (infiltration-percolation and constructed wetlands): a solution for small communities.

The decision on technologies used for reclaiming wastewater appears as important as a consequence of the implications on the economic, environmental and health conditions of societies. The problem arises when deciding how to deal with wastewater in small communities, because the costs of implementing and operating small, intensive wastewater treatment plants are unacceptable and can lead to financing and operation problems. Extensive treatment systems can be a good solution, where space is available. This paper presents the combination of two soft technologies (infiltration-percolation and constructed wetlands) to treat and reclaim wastewater. The obtained results show that the infiltration-percolation effluent presents a quality enough to be reused for irrigation of industrial crops, nurseries, fodder, cereals and oleaginous seeds, ornamental flower production; industrial cooling; impoundments, water bodies, and streams for recreational use in which the public's contact with the water is not permitted; and irrigation of forested areas, landscape areas and restricted access areas. Moreover, the combination of infiltration-percolation and constructed wetlands increases the list of final reclamation to the following: irrigation of pasture for milk or meat animals, crops for canning industry, crops not raw-consumed, fruit trees except by sprinkling, aquaculture; and aquifer recharge by localised percolation through the soil.

Wastewater reclamation systems in small communities.

The demands established in the rules and regulations by the administration in Catalonia seem to exclude small communities from wastewater reclamation and reuse, due to the comparatively high costs associated with the practice at small scale. In the framework of the DRAC project (Demonstration on Wastewater Reclamation and Reuse in Catalonia) two different pre-treatment systems, one extensive (infiltration-percolation) and another intensive (ring filter), each one followed by chlorine dioxide disinfection, were tested in order to be applied for small communities wastewater reclamation and reuse. The results of this study show that infiltration-percolation systems remove very efficiently physico-chemical contaminants and microorganisms. The ring filter system does not show a significant removal rate of contaminants, The use of infiltration-percolation as a pre-treatment for advanced chemical disinfection allows reducing the dose of disinfectant and the contact time needed to achieve a specific water quality, and diminishes disinfection byproducts (DBPs) generation. Therefore, this reclamation line is suitable for small communities due to its efficiency and low cost. However, further studies are needed in relation to the removal mechanisms of microorganisms, organic compounds in IP systems and the possible DBPs formation using chlorine dioxide.

Wastewater infiltration percolation for water reuse and receiving body protection: thirteen years' experience in Spain.

Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents of small and middle size communities before reuse or disposal to sensitive receiving bodies. Thirteen years of implementation of IP in Spain has highlighted the necessity to abide by defined design and construction rules and operation conditions in order to achieve consistently the treatment objectives and guarantee a long lasting treatment capacity. From this experience, high care should be taken of (i) the characteristics of the sand constituting the filter, (ii) the drainage conditions, (iii) the influent spreading over the infiltration surface and (iv) the risks related to recurrent overloading. Simple monitoring measures are suggested in order to improve the reliability of IP plants.

Development of a knowledge-based decision support system for identifying adequate wastewater treatment for small communities.

The identification of adequate treatment for small communities is a complex problem since it makes it necessary to combine aspects of the community and landscape, the receiving environment, and the available wastewater treatment technologies. This paper presents the development and implementation of a Knowledge-Based Decision Support System (KB-DSS) to tackle this problem. Different knowledge sources have been consulted in order to make up a comprehensive and accurate knowledge base. The core of the KB-DSS embraces two objectives. The first one is to assist in the selection of the treatment level adequate to fulfil the target quality standards for the receiving environment. The second one is to select the specific type of treatment. The KB-DSS is being applied to each one of the 3,482 different small communities comprised in the Small Communities Wastewater Treatment Plan of Catalonia, grouped according to river catchments. This paper also summarizes the different steps involved in the operation of the knowledge-based DSS when solving a real case study.

Secondary wastewater disposal for crop irrigation with minimal risks.

A critical objective for any wastewater reuse program is to close the gap between supply of and demand for water and to minimize health and environmental hazards. Thus, the effects of treated effluent on crops, soils and community health must be considered carefully. When applying wastewater to soil-plant systems, it is to be noted that the passage of water through the soil reduces considerably the number of microorganisms carried out by the reclaimed wastewater. Nevertheless, there is a need to study the real rate of organism decay subject to water quality, soil and vegetable characteristics, and irrigation method. The aim of this work is to determine the fate of the fecal coliforms, coliphages F+ and CN13, and helminth eggs survival during the application of reclaimed wastewater in a vineyard orchard near the City of Arad (Israel) via onsurface and subsurface drip irrigation systems. Wastewater obtained from a stabilization pond, and soil samples were tested and an important decrease of microorganisms was reached in both cases, with the better values obtained with the sub-surface drip irrigation system.

Biological control tools for wastewater reclamation and reuse. A critical review.

The health related risk of wastewater reclamation and reuse is usually defined by laws, rules or regulations by using only biological tools; i.e. bacteria, viruses, or other pathogens or indicators determination. Those determinations exert some influence in the costs of the mentioned practices, and it seems probable that in the near future more determinations will be required. Nevertheless, a total indication of wastewater biological quality is not given by such organisms; in fact, long-term toxicity is not detected by such means. The future of biological control of reclamation and reuse systems and the price associated to such determinations is examined through a practical application case.

Role of water reuse for enhancing integrated water management in Europe and Mediterranean countries.

Recycling water is an important aspect of water resource and environment management policies, ensuring reliable alternative water resources, reducing environmental pollution and achieving a more sustainable form of development. This paper focuses on wastewater reuse as a strategy for integrated water management. Key economic, financial, regulatory, social and technical factors that help to make water reuse projects successful are reviewed. Selected examples from Northern and Western Europe and arid and semi-arid Mediterranean regions illustrate the contribution of wastewater reuse to integrated management of water resources.