Municipal solid waste (MSW) reflects the culture that produces it and affects the health of the people and the environment surrounding it. Globally, people are discarding growing quantities of waste, and its composition is more complex than ever before, as plastic and electronic consumer products diffuse. Concurrently, the world is urbanizing at an unprecedented rate. These trends pose a challenge to cities, which are charged with managing waste in a socially and environmentally acceptable manner. Effective waste management strategies depend on local waste characteristics, which vary with cultural, climatic, and socioeconomic variables, and institutional capacity. Globally, waste governance is becoming regionalized and formalized. In industrialized nations, where citizens produce far more waste than do other citizens, waste tends to be managed formally at a municipal or regional scale. In less-industrialized nations, where citizens produce less waste, which is mostly biogenic, a combination of formal and informal actors manages waste. Many waste management policies, technologies, and behaviors provide a variety of environmental benefits, including climate change mitigation. Key waste management challenges include integrating the informal waste sector in developing cities, reducing consumption in industrialized cities, increasing and standardizing the collection and analysis of solid waste data, and effectively managing increasingly complex waste while protecting people and the environment.

Crete, located in the South Mediterranean Sea, is characterized by long coastal areas, varied terrain relief and geology, and great spatial and inter-annual variations in precipitation. Under average meteorological conditions, the island is water-sufficient (967 mm precipitation; theoretical water potential 3425.89 hm³; and total water use 610 hm³). Agriculture is by far the greatest user of water (78% of total water use), followed by domestic use (21%). Despite the high average water availability, water scarcity events commonly occur, particularly in the eastern-south part of the island, driven by local climatic conditions and seasonal or geographical mismatches between water availability and demand. Other critical issues in water management include the over-exploitation of groundwater, accounting for 93% of the water used in agriculture; low water use efficiencies in the farms; limited use of non-conventional water sources (effluent reuse); lack of modern frameworks of control and monitoring; and inadequate cooperation among stakeholders. These deficiencies impact adversely water use efficiency, deteriorate quality of water resources, increase competition for water and water pricing, and impair agriculture and environment. Moreover, the water-limited areas may display low adaptation potential to climate variability and face increased risks for the human-managed and natural ecosystems. The development of appropriate water governance frameworks that promote the development of integrated water management plans and allow concurrently flexibility to account for local differentiations in social-economic favors is urgently needed to achieve efficient water management and to improve the adaptation to the changing climatic conditions. Specific corrective actions may include use of alternative water sources (e.g., treated effluent and brackish water), implementation of efficient water use practices, re-formation of pricing policy, efficient control and monitoring, and investment in research and innovation to support the above actions. It is necessary to strengthen the links across stakeholders (e.g., farmers, enterprises, corporations, institutes, universities, agencies, and public authorities), along with an effective and updated governance framework to address the critical issues in water management, facilitate knowledge transfer, and promote the efficient use of non-conventional water resources.

According to FAO, water scarcity is now affecting all five continents and is expected to intensify in the coming years as the water demands of the growing population increase and the impacts of climate variability become more pronounced. The existing unevenness of water resource availability and insufficient investment in relevant infrastructure have forced the water sector to recognize the importance of nonconventional water resources (NWR) in planning for a sustainable water future. The purpose of this review is to highlight the available and potentially available NWR and to discuss the future application of these water sources.

Decentralized wastewater management (DWM) may be defined as the collection, treatment, and reuse of wastewater from individual homes, clusters of homes, subdivisions, and isolated commercial facilities at or near the point of waste generation. In some areas, the liquid portion could be transported to a central point for further treatment and reuse. At the time of writing (2002), more than sixty million people in the United States live in homes where individual decentralized systems are used for wastewater management. Further, the U.S. EPA now estimates that about 40 percent of the new homes being built are served with onsite systems. In the early 1970s, with the passage of the Clean Water Act, it was often stated that it was only a matter of time before sewerage facilities would be available to almost all residents of the continental United States. Now, more than 25 years later, it is recognized that complete sewerage of the entire U.S. may never be possible, due to both geographic and economic constraints. Because complete sewerage is unlikely in the foreseeable future, it is clear that DWM systems are needed for the protection of public health and the environment and for the development of long-term strategies for the management of our water resources. The challenges and opportunities for DWM systems in the twenty-first century are discussed in this paper.

Population growth, the impacts of climate change, and the need for greater water security have made the reuse of wastewater, including potable use, increasingly desirable. As interest in potable reuse of wastewater increases, a variety of processes have been proposed for advanced water treatment following conventional wastewater treatment. In all cases, the operation and performance of advanced water treatment facilities (AWTFs) is improved when the treated wastewater feed is of the highest quality that can be achieved and the advanced water treatment (AWT) processes are operated at a constant flow. One proven method of optimizing the performance of wastewater treatment facilities (WWTFs) is constant flow operation with no extraneous return flows other than internal process recycle flows, such as return settled solids. A number of approaches can be used to achieve constant flow including flow equalization, divided treatment trains, and satellite treatment. The ways in which constant flow wastewater treatment benefits both WWTFs as well as the AWTFs are considered with special emphasis on the ability to achieve predictable log removal credits (LRCs) for specific microorganisms. Actual performance data from constant flow WWTFs are used to illustrate how LRCs are determined.Practitioner points: Constant flow WWTFs should be considered to produce the highest quality secondary effluent for AWT. Flow equalization, divided treatment trains, and satellite treatment can be used to achieve constant flow to optimize wastewater treatment in small and medium size WWTFs. Flow equalization can be used to maximize the amount of wastewater that can be recovered for potable reuse. Important benefits of constant flow for wastewater treatment facilities include economic and operational savings, stable and predictable treatment performance, energy savings, ability to optimize performance for the removal of specific constituents, and the ability to assign pathogen log removal credits (LRCs). Important benefits of constant flow and optimized WWT for AWTFs include economic and operational savings; less pretreatment needed, including energy and chemical usage; elimination of the need to cycle treatment processes; and added factor of safety with respect to the required pathogen LRCs. In large WWTFs, constant flow for AWTFs will typically be achieved by effluent diversion; depending on the effluent quality additional pretreatment may be needed. The design and implementation of WWTFs and AWTFs for potable reuse should be integrated for optimal performance and protection of public health.

The state of California has passed legislation to divert organic materials from landfills to reduce the emission of methane to the atmosphere. A large amount of this source separated organic (SSO) material is expected to be used as a feedstock for anaerobic digestion processes. Based on a review of properties for likely SSO feedstocks, it is clear that while SSO are high in volatile solids, they are also concentrated sources of nutrients (principally, ammonium). When SSO feedstocks are digested, these nutrients are released into the digestate, where ammonium can cause problems both within the digester and in downstream treatment processes. The focus of this paper is on the performance of two pilot studies designed to remove ammonia from a digester effluent. The process used in the study is a thermal stripping column with tray configuration, operating under a vacuum. In the first study, food waste digestate was treated as a slurry in the stripping column with and without NaOH addition. At process temperatures near 90 °C, the performance with and without caustic was similar. In the second study, centrate from a co-digestion facility, that blends food processing waste with wastewater process solids, was treated in the same thermal stripping column under the same conditions and without chemical addition. The results from both studies, which can be described using the same performance curves, are presented and discussed in this paper.