As demand for fresh water intensifies, wastewater is frequently being seen as a valuable resource. Furthermore, wise reuse of wastewater alleviates concerns attendant with its discharge to the environment. Globally, around 20 million ha of land are irrigated with wastewater, and this is likely to increase markedly during the next few decades as water stress intensifies. In 1995, around 2.3 billion people lived in water-stressed river basins and this could increase to 3.5 billion by 2025. We review the current status of wastewater irrigation by providing an overview of the extent of the practice throughout the world and through synthesizing the current understanding of factors influencing sustainable wastewater irrigation. A theme that emerges is that wastewater irrigation is not only more common in water-stressed regions such as the Near East, but the rationale for the practice also tends to differ between the developing and developed worlds. In developing nations, the prime drivers are livelihood dependence and food security, whereas environmental agendas appear to hold greater sway in the developed world. The following were identified as areas requiring greater understanding for the long-term sustainability of wastewater irrigation: (i) accumulation of bioavailable forms of heavy metals in soils, (ii) environmental fate of organics in wastewater-irrigated soils, (iii) influence of reuse schemes on catchment hydrology, including transport of salt loads, (iv) risk models for helminth infections (pertinent to developing nations), (v) microbiological contamination risks for aquifers and surface waters, (vi) transfer efficiencies of chemical contaminants from soil to plants, (vii) health effects of chronic exposure to chemical contaminants, and (viii) strategies for engaging the public.

http://dro.deakin.edu.au/eserv/DU:30007424/stagnitti-wastewaterirrigation-2007.pdf

Wastewater irrigation: The state of play

Anaerobic digestion of wastewater should be a core technology employed in decentralised sanitation systems especially when their objective is also resource conservation and reuse The most efficient system involves separate collection and anaerobic digestion of the most concentrated domestic wastewater streams: black or brown water and solid fraction of kitchen waste Separate collection using minimal amount of transport water besides saving this resource allows to apply a targeted treatment A relatively small volume of digested effluent can be directly reused for fertilisation or processed when a high quality product is required Clean nutrient production requires advanced multi-step treatment but the quality of products is risk-free The issue of organic micro-pollutants and their accumulation in the environment is recently often addressed Anaerobic treatment of total domestic wastewater stream can be applied as well Treated in this way wastewater can be discharged or used for irrigation or fertilisation The post-treatment will be usually required and its rate of complexity depends on the anaerobic effluent quality and local requirements for final effluent quality A variety of technological solutions for treatment of domestic wastewater streams and reuse of resources is discussed in this paper

Anaerobic treatment in decentralised and source-separation-based sanitation concepts

Sustainable sanitation technology options for urban slums

Biologically produced hydrogen (biohydrogen) is a valuable gas that is seen as a future energy carrier, since its utilization via combustion or fuel cells produces pure water. Heterotrophic fermentations for biohydrogen production are driven by a wide variety of microorganisms such as strict anaerobes, facultative anaerobes and aerobes kept under anoxic conditions. Substrates such as simple sugars, starch, cellulose, as well as diverse organic waste materials can be used for biohydrogen production. Various bioreactor types have been used and operated under batch and continuous conditions; substantial increases in hydrogen yields have been achieved through optimum design of the bioreactor and fermentation conditions. This review explores the research work carried out in fermentative hydrogen production using organic compounds as substrates. The review also presents the state of the art in novel molecular strategies to improve the hydrogen production.

Fermentative biohydrogen production: trends and perspectives

Volatile fatty acids production during mixed culture fermentation – The impact of substrate complexity and pH

Anaerobic conversion of organic materials and pollutants is an established technology for environmental protection through the treatment of wastes and wastewater. The end product is biogas –a mixture of methane and carbon dioxide–, which is a useful, renewable energy source. Anaerobic digestion is a technologically simple process, with a low energy requirement, used to convert organic material from a wide range of wastewater types, solid wastes and biomass into methane. A much wider application of the technology is desirable in the current endeavours towards sustainable development and renewable energy production. In the 1980’s several projects were initiated in The Netherlands to produce biogas from wastes. Many projects were terminated due to insufficient economic viability. Currently, the production of methane from wastes is receiving renewed attention as it can potentially reduce CO2 emissions via the production of renewable energy and limit the emission of the greenhouse gas methane from especially animal manure. This trend is supported by the growing market demand for ‘green’ energy and by the substantial optimisation of anaerobic digestion technologies in the past decades, especially the development of modern ‘high rate’ and co-digestion systems.

T.Z.D. de Mes

Papers

Methane production by anaerobic digestion of wastewater and solid wastes

Fate of oestrogens during anaerobic blackwater treatment with micro-aerobic post-treatment.

Designing sustainable sanitation in urban planning proposed for Changzhou, China.

Oestrogen removal from biological pretreated wastewater within decentralised sanitation and re-use concepts.

Anaerobic digestion and physiological waste and kitchen refuse towards resource management in the DESAR concept