Dyes are an important class of organic pollutants and are well known for their hazardous effects on aquatic life in general and human beings in particular. In order to reduce the negative effects of dye contaminated wastewater on humans and the environment, the wastewater must be treated carefully before discharge into main streams. Advances in science and technology have led to the evolution of several techniques for the removal of dyes from industrial and domestic effluents. In this review, the more recent methods for the removal of dyes from water and wastewater have been discussed. Wastewater treatment techniques such as adsorption, oxidation, flocculation–coagulation, membrane filtration and biological treatment have been highlighted. In addition, efforts were made to review all the available techniques and recently published studies from 2010–2014. Furthermore, the performance and special features of these technologies have been summarised. Advantages and limitations of each technique are also presented. A thorough literature survey revealed that chemical oxidation, adsorption, and biological treatments have been the most frequently investigated techniques for dye removal over the past few years.

https://pubs.rsc.org/en/content/articlepdf/2015/ra/c4ra16959j

Recent advances in new generation dye removal technologies: novel search for approaches to reprocess wastewater

A comprehensive review of electrocoagulation for water treatment: Potentials and challenges.

Electrocoagulation and advanced electrocoagulation processes: A general review about the fundamentals, emerging applications and its association with other technologies

An overview of oil-water separation using gas flotation systems.

Bio-based fertilizers: A practical approach towards circular economy.

During the last two decades, and particularly during the last few years, the environmental sector has shown a largely growing interest in the treatment of different types of water and wastewater by electrocoagulation (EC). The aim of this work was to review studies, conducted mainly during 2008-2011, on the wide and versatile range of feasible EC applications employed in the purification of different types of water and wastewater. The EC applications discussed here were divided into 7 following categories: tannery, textile and colored wastewater; pulp and paper industry wastewater; oily wastewater; food industry wastewater; other types of industrial wastewater; surface water as well as model water and wastewater containing heavy metals, nutrients, cyanide and other elements and ions. In addition, this paper presents an overview of the optimum process conditions (treatment times, current densities, and initial pH) and removal efficiencies (mostly high) achieved for the EC applications discussed. In the vast majority of the studies discussed in this review, the aforementioned values were found to be in the range of 5 - 60 min (typically less than 30 min), 10 - 150 A/m 2 and near neutral pH, respectively. Both operating costs and electrical energy consumption values were found to vary greatly depending on the type of solution being treated, being between 0.0047 - 6.74 €/m 3 and 0.002 - 58.0 kWh/m 3 , but in general they were rather low (typically around 0.1 - 1.0 €/m 3 and 0.4 - 4.0 kWh/m 3

/pdf/recent-applications-of-electrocoagulation-in-treatment-of-4athqfc3jc.pdf

Recent Applications of Electrocoagulation in Treatment of Water and Wastewater—A Review

The electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30 mg/l) was optimized, followed by successful scale-up experiments. The optimum process conditions (96% phosphate removal) for laboratory-scale SSW were found to be: anode/cathode = Al/Fe (although Fe/Al performed similarly), initial pH = 5, current density = 100 A/m 2 , treatment time = 15 min, supporting electrolyte = 1.0 g/l NaCl and electrode gap = 7 mm. Real industrial phosphate-containing mining wastewater (MWW) and dairy wastewater (DWW) were also treated with EC, with high pollutant removal efficiencies (optimal phosphate removal of 79% and 93% in 30 min and 60 min, respectively) achieved over the wide initial pH range studied. Electricity consumption and operating costs values in optimum conditions were low for all wastewaters: 0.75 kWh/m 3 and 0.17 €/m 3 for SSW (laboratory scale), 2.11 kWh/m 3 and 0.28 €/m 3 for MWW, and 1.46 kWh/m 3 and 0.31 €/m 3 for DWW. To summarize, the feasibility of using EC in removing phosphate from the wastewater types studied was proven. Utilization of the resulting EC sludge – a potentially valuable phosphorus source in the future (especially in granulated bio ash-based fertilizer products) – was also studied and is discussed.

Removal of phosphate from wastewaters for further utilization using electrocoagulation with hybrid electrodes – Techno-economic studies

Bench scale electrocoagulation studies of bio oil-in-water and synthetic oil-in-water emulsions

Both the current growth strategy and environmental policies of the European Union (EU) aim to increase the amount of renewable energy and to improve the use of waste streams. This will increase the amount of bio-ash from biomass combustion in the future, thereby increasing the need for its utilization, with fertilizer use the most natural target for bio-ash. Wood ash, in particular, contains all the nutrients that plants need, in almost the correct proportions, excluding nitrogen, which is released into the atmosphere during combustion. Nitrogen could be added to ash fertilizers by co-granulating bio-ash, for example, with sewage sludge. However, co-granulation has not been studied extensively. This study investigated co-granulation of bio-ash with sewage sludge and lime. It measured compressive strengths, neutralizing values, and elemental concentrations of the granules. The concentrations of heavy metals (As, Cd, Cr, Cu, Pb, Ni, and Zn) in the granules were sufficiently low not to prevent their use in forest fertilizer use according to Finnish legislation. Overall, the concentrations of nutrients (Ca, K, and P) were reasonably high. The addition of lime improved the neutralizing capacity of the studied granules, and the addition of sewage sludge increased their nitrogen content. The addition of sewage sludge considerably lowered the compressive strength of the granules, and the addition of lime (slaked lime) did not improve the strength of the granules. From a technical point of view, the co-granulation was very successful.

V. Kuokkanen

Papers

Recent Applications of Electrocoagulation in Treatment of Water and Wastewater—A Review

Removal of phosphate from wastewaters for further utilization using electrocoagulation with hybrid electrodes – Techno-economic studies

Bench scale electrocoagulation studies of bio oil-in-water and synthetic oil-in-water emulsions

Co-granulation of bio-ash with sewage sludge and lime for fertilizer use

Electrocoagulation treatment of peat bog drainage water containing humic substances.