Water purification is one of the inevitable problems affecting people throughout the world. Effluents resulting from industrial activities are the most problematic and challenging wastewaters and have become a concern, as scarcity and costs of water both become more evident. The development and implementation of solutions to enhance water treatment are crucial.
Several traditional and advanced technologies have been applied to treat wastewaters, and flocculation still remains a vital process, extensively used in separation processes applied in many industrial effluents treatment procedures, both on its own or complementing other treatments. This process is able to separate impurities, using a simple, versatile and low energy treatment methodology.
Synthetic charged polymers, such as polyacrylamide and its derivatives, are extensively used as flocculants for wastewater treatment, due to their ability to easily adsorb to the impurity particles by oppositely charges attraction. Polymers with very long chains and medium to high amount of charges have been applied as flocculants in direct flocculation or combined with inorganic coagulants like aluminum, ferric chloride or ferric sulfate since they contribute to increase flocculation speed and thus reduce the treatment time.
The development of suitable flocculation products to optimize the process performance is very important. Moreover, the concern with environmental and health issues is increasing, shifting the research towards the use of more eco- and health-friendly alternatives to the products commonly used in numerous industries as flocculants. Hence, to meet the actual health requirements, specific customized products for a target application must be developed using health-friendly approaches.
Some of the flocculants mentioned previously have been conventionally produced using recipes presenting only a mild health concern, as they are produced with solvents/oils, which are irritant and comprise unsafe components, which at residual levels may not be toxic, but can present long-term health effects. Consequently, there is still a need for alternative production ingredients that allow for obtaining final products (flocculants) with comparable efficiencies to the ones produced using traditional compounds, but applying now health-friendly constituents.
The alternatives suggested in this work comply with many pharmacopeias and FDA regulations, are non-irritating, and free of harmful ingredients. These alternative media were used to produce a well-known flocculant, commonly used in wastewater treatment, which was then applied for treatment of oily wastewaters from two different industries.
Oily wastewaters are generated in many industrial processes, related, in general to three main activities: the petroleum industry, via crude oil extraction and oil refineries; the manufacturing of metal pieces in metalworking industries, which produce oily wastewaters resulting from the use of cutting, cooling and lubricating fluids, as well as during cleaning operations; and finally, food processing industries, including production and transformation of both animal and vegetable products, which also produce large volumes of oily wastewaters (meat processing, dairy industries, refining of vegetable oils from sunflower, cotton-seed, soybean or rapeseed, palm and olive oil mill facilities, etc.). Among the extensive list of possible industrial oily effluents, the present work focused only on two of them: dairy effluents and potato crisps manufacturing effluent, considering their importance in Portugal.
Final results revealed the successful development of a more eco-friendly production recipe to synthesize flocculants that can be applied in oily effluents treatment. It was also possible to prove the success of the application of the products developed in flocculation of the two real industrial wastewaters, achieving in both cases clarifications of wastewaters above 70%, with the suitable product.
These findings are described in the article entitled A more eco-friendly synthesis of flocculants to treat wastewaters using health-friendly solvents, published in the journal Colloid and Polymer Science. This work was led by Maria G. Rasteiro from the University of Coimbra.
This project is being developed with the support of the European grant, FP7-PEOPLE-2013-ITN- 604825 – ECOFLOC optimize.