Wastewater

About: Wastewater is a research topic. Over the lifetime, 92512 publications have been published within this topic receiving 1256590 citations. The topic is also known as: waste water.

Drivers and characteristics of wastewater agriculture in developing countries: results from a global assessment.

Abstract: In many cities of developing countries untreated wastewater and polluted water are used for agriculture in urban and peri-urban areas. Though such practices are a threat to the health of users and consumers, they do provide important livelihoods benefits and perishable food to cities. This paper through a cross country analysis of 53 cities in the developing world, provides an understanding of the factors that drive wastewater use. The 53 cities represent a range of settings in arid and wet areas, in rich and poor countries, and coastal as well as inland cities to provide a picture of wastewater use globally. It relates the wastewater collection and disposal practices to the increasing impact of poor water quality on agriculture. The study shows that the main drivers of wastewater use in irrigated agriculture are in most cases a combination of three factors: − Increasing urban water demand and related return flow of used water, either treated or untreated, into the environment and its water bodies, causing pollution of traditional irrigation water sources. − Urban food demand and market incentives favouring production in city proximity where water sources are usually polluted. − Lack of alternative (cheaper or safer) water sources. Additionally, poverty and migration play a secondary role; where cities are unable to treat wastewater due to lack of resources, where poor farmers use available water sources whatever the quality; and where migration results in urban and peri-urban agriculture as a means of livelihood support. Use of untreated wastewater is not limited to the countries and cities with the lowest GDP, and is prevalent in many mid-income countries as well. In four out of every five cities surveyed wastewater is used (treated, raw or diluted) in urban and peri-urban agriculture even if areas cultivated in each of the cities may sometimes be small. Across 53 cities we conclude that just for these cities alone, approx 0.4 million ha are cultivated with wastewater by a farmer population of 1.1 million with 4.5 million family dependants. Compiling information from various sources, the total number of farmers irrigating worldwide with treated, partially treated and untreated wastewater is estimated at 200 million; farming on at least 20 million hectares. These figures include areas where irrigation water is heavily polluted. Though the actual physical areas under cultivation may be small, some crops are grown at least 10 times a year. Data from a detailed city study in Accra showed that about 200,000 urban dwellers benefit everyday from vegetables grown on just 100 ha of land. Strict irrigation water quality guidelines cannot be imposed where traditional irrigation water sources are polluted, unless alternative sources of water are provided. Farmers are aware of potential risks to themselves and to consumers but a clear understanding of cause and effect are missing. The fact that consumers in cities habitually wash vegetables supports the idea that the best method of minimizing risk in the short term would be to encourage effective washing of vegetables. Some key policy recommendations made are: 1. Urban and peri-urban agriculture can enhance food supplies to cities and is an effective source of nutrition which can be improved at very little marginal cost.

Polyelectrolyte-Promoted Forward Osmosis–Membrane Distillation (FO–MD) Hybrid Process for Dye Wastewater Treatment

Abstract: Polyelectrolytes have proven their advantages as draw solutes in forward osmosis process in terms of high water flux, minimum reverse flux, and ease of recovery. In this work, the concept of a polyelectrolyte-promoted forward osmosis–membrane distillation (FO–MD) hybrid system was demonstrated and applied to recycle the wastewater containing an acid dye. A poly(acrylic acid) sodium (PAA-Na) salt was used as the draw solute of the FO to dehydrate the wastewater, while the MD was employed to reconcentrate the PAA-Na draw solution. With the integration of these two processes, a continuous wastewater treatment process was established. To optimize the FO–MD hybrid process, the effects of PAA-Na concentration, experimental duration, and temperature were investigated. Almost a complete rejection of PAA-Na solute was observed by both FO and MD membranes. Under the conditions of 0.48 g mL–1 PAA-Na and 66 °C, the wastewater was most efficiently dehydrated yet with a stabilized PAA-Na concentration around 0.48 g mL–...

Characterization of dissolved organic matter in municipal wastewater using fluorescence PARAFAC analysis and chromatography multi-excitation/emission scan: a comparative study.

Abstract: Dissolved organic matter (DOM) in municipal wastewater was mainly characterized using high-performance liquid chromatography (HPLC) and size exclusion chromatography (HPSEC) with multi-excitation/emission fluorescence scan. Meanwhile, fluorescence excitation-emission-matrix combined with parallel factor analysis (EEM-PARAFAC) was also applied. Compared with chromatography fluorescence fingerprints, the EEM-PARAFAC model could not reflect the variety of DOM species with similar fluorescence but different physicochemical properties. The chromatography results showed that the protein-like species were variable among different municipal wastewater treatment plants, some of which are in combination with humic-like species; while there were two major humic-like species fractionated by hydrophilicity and molecular weight (MW), which are also the major contributors to UV absorbance at 254 nm. It was also identified that the relatively hydrophilic humic fractions were slightly larger than the relatively hydrophobic humic fractions. In all the investigated wastewater treatment plants, the relatively hydrophilic and larger MW humic fraction mainly contributed to the fluorescence intensity of humic-like EEM-PARAFAC components. As well as facilitating interpretations of EEM-PARAFAC components, the HPLC/HPSEC fluorescence fingerprints also contributed to a better understanding of fluorescent DOM species in municipal wastewater.

Overview and description of technologies for recovering phosphorus from municipal wastewater

Abstract: Over the past years, numerous technologies have been developed to recover phosphorus (P) from waste streams to repair currently broken nutrient cycles. These developments were largely triggered by environmental considerations (sustainability, resource efficiency), concerns regarding the finite and geopolitically concentrated deposits of raw phosphate ore, and phosphate price increases. Municipal wastewater is a promising and viable source to recover P in larger quantities, to re-establish a circular economy and therefore increase net use efficiency. This work compiles the latest knowledge on approaches to recover P from municipal wastewater and related waste flows with a specific focus on the existing well-developed wastewater management infrastructure, available in significant parts of Europe (e.g., secondary treated effluent, digester supernatant, sewage sludge, sewage sludge ash). About 50 technologies were identified at various levels of development (industrial-, full-, pilot- and laboratory scale). The current selection of P recovery processes is broad and ranges from simple precipitation of dissolved P to complex multi-step approaches, and only a few of these displayed potential for full-scale implementation. They are discussed with regard to their technical principles, process parameters, recovery efficiency, resource demand, possible effects on wastewater treatment, waste flows, and fate of pollutants. We also evaluated them with respect to their rates of P removal from wastewater and their access points of P recovery. For selected technologies, material flow models are presented to facilitate the understanding of even complex processes. This work serves as a basis for future integrated comparative assessments of selected recovery approaches according to technical, environmental and economic criteria.

Adsorption of heavy metal ions by various low-cost adsorbents: a review

Abstract: Environmental pollution, particularly from heavy metal ions in the wastewater, is one of the most serious concerns of the world. In the pursuit of remedial action, various conventional methods such...