To employ technologies that sustainably harvest resources from wastewater (for example struvite granules shown here), new perceptions and infrastructure planning and design processes are required.Water and wastewater system decisions have been traditionally driven by considerations of function, safety, and cost-benefit analysis. The emphasis on costs and benefits would be acceptable if all relevant factors could be included in the analysis, but unfortunately many relevant factors are routinely excluded. Coupled with failures to fully engage the public in decision-making processes, this can impede progress toward achieving sustainable solutions. Ignoring broader social issues that impact the adoption of sustainable solutions prolongs not only global environmental and ecological problems, but also unjust public health and social conditions in the developing world.Within the water and wastewater management industry, discussions of sustainable development have often focused on water stress (1, 2): a hazard that is exacerbated by other global stressors such as climate change, demographic and land use changes, increasing population, and urbanization (2). In addition to water stress, water and wastewater management practices contribute to nutrient imbalances and a host of environmental detriments such as eutrophication (3), discharge of pharmaceuticals and other emerging contaminants (4), and a loss of biodiversity in receiving streams (5). Efforts to address these issues across regional and global scales are hindered by the historical disconnect between the water quality and water quantity factions of the water profession. Although our understanding of sustainability is constantly evolving, the water and wastewater design process retains its foundation in engineering traditions established in the early 20th century (6). As we chart a path in the 21st century, we contend that wastewater contains resources worthy of recovering and that the development of
Enhanced biological phosphorus removal (EBPR) was observed in high-rate, non-nitrifying plants in the United States that were operated in a plug-flow mode. In facilities designed for nitrification and denitrification, a first-stage anaerobic zone, free of nitrate and nitrite was needed to accomplish EBPR, and this is referred to as the Phoredox (a.k.a. the AO and A2O) process. When a biological mechanism responsible for EBPR was proposed, these treatment configurations were accepted as normal practice, but many later observations showed that more reliable phosphorus removal could be achieved with alternative configurations. This paper discusses the development of alternative configurations for EBPR and the likelihood that a host of phosphate accumulating organisms (PAOs) that react to different environmental conditions might play a much bigger role in reliable and sustainable biological phosphorus removal. The conclusion is that conventional designs might have inadvertently selected for less efficient PAOs, while alternative configurations allowed for the growth of multiple PAO species such as Tetrasphaera, which can ferment higher carbon forms and take up phosphorus under anoxic conditions.
The European Union (EU) has implemented effluent (emission) standards since 1991, while North America practices a riskbased, imission approach. Progressing eutrophication and large fees for discharged loads push EU countries toward more stringent effluent concentrations, below total nitrogen (TN) levels of 10 mg/L and total phosphorus (TP) levels of 1 mg/L. In North America, the limit of treatment technology (LOT) concept has been defined as the lowest economically achievable effluent quality, which for TN is <1.5 to 3 mg/L and TP is <0.07 mg/L. These limits are becoming targets in fragile ecoregions in North America and drive the technology solutions towards a combination of advanced biological nutrient removal process trains, followed by chemical polishing and solids separation by granular or cloth filters or membranes. In Western Canada one-biomass biological nutrient removal processes are used, such as Westbank or Step-feed, often followed by filtration to achieve low effluent total phosphorus levels. Eastern Canada has a less stringent approach to nitrogen control and practices chemical phosphorus removal. Requirement for total nitrogen removal and rising costs of phosphorus precipitation drive designers towards advanced one-biomass processes and full utilization of carbon (for denitrification and phosphorus removal) available in raw wastewater and primary sludge. New processes are developed to take advantage of carbon available in waste activated sludge or even in the recycled activated sludge. Sludge treatment return streams have high nutrient loads and novel processes are introduced for their treatment, some utilizing generated nitrifier biomass for bio-augmentation of the main stream nitrification process. The impact of sludge processing on the liquid train and vice versa is now fully embedded in the design process.
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