PROJECT DESCRIPTION
BACKGROUND
Currently in Europe, 44 000 million m3/year of drinking water are produced. For its purification, inorganic polyaluminium coagulants (PAC), polyaluminium chloride (PACl), in concentrations of 20-30 mg/L, are used in drinking water treatment plants. Likewise, synthetic organic coagulants, such as polyacrylamides, have been used, although their use is limited by the World Health Organization to 0.5 g/L. Negative impacts on human health and the environment are associated with the use of synthetic coagulants. In fact, the use of PAC, PACI and polyacrylamide is currently being questioned for several reasons. Environmental problems arise mainly due to the generation of toxic sludge containing aluminium and acrylamide that cannot be used in agriculture or recovered for the creation of new wastewater treatment infrastructures, such as wetlands. Residual concentrations of aluminium in drinking water have been connected with neurotoxicity, Alzheimer's disease and breast cancer. Residual concentrations of acrylamide monomers are linked with neurotoxicity and alteration of reproductive function. Modification of the pH during water treatment also makes the process more expensive and less sustainable.
Overall, drinking water treatment is based on multiple stages, whose objective is to obtain an effluent of adequate quality and suitable for human consumption. During the coagulation-flocculation stage, a physical-chemical process is carried out to eliminate colloidal suspended matter and reduce microorganisms associated with turbidity. This process has a direct influence on the optimisation of subsequent stages, sedimentation or filtration among others, and directly affects the final quality of the purified water. Taking into consideration the above, and the restrictions on the use of dangerous substances in the regulations of the European Union Member States, there is growing interest in the development of new natural organic coagulants that are not toxic to humans and that have a lower impact on the environment.
OBJECTIVES
The main objective of LIFE SAFE_T_WATER was to validate an innovative and environmentally-friendly technology for drinking water production in 2 Drinking Water Treatment Plants (DWTP) located in Spain (treating a portion of the overall 1.13 hm3/d of water that supplies drinking water to 5.5 million inhabitants). The project beneficiaries aimed to demonstrate a new technology that eliminates all the corrosive and dangerous chemical products in the DWTP process, including corrosive inorganic salts (coagulation), carcinogenic polyacrylamide-based polymers (flocculation), and toxic inorganic neutralising agents (pH adjustment). The chemical products of 3 steps in the treatment - coagulation, flocculation and pH adjustment - were replaced by a single multifunctional enhanced-organic polymer based on natural extracts.
In terms of EU policy, the project sought to contribute to the Water Framework Directive (2000/60/EC), by minimising the environmental impact of effluents, and the Groundwater Directive (2006/118/EC), by introducing measures to limit or prevent discharges of pollutants into groundwater.
RESULTS
The project was not implemented as foreseen. However, partial results were achieved.
The LIFE SAFE_T_WATER project focused on enhancing the efficiency of water treatment processes by using natural coagulants derived from organic polymers. These coagulants were tested at pilot scales in 2 drinking water treatment plants located in Valencia (La Presa) and Madrid (Colmenar Viejo). The pilot tests demonstrated that the natural coagulants could effectively remove 100% of the aluminium input (from polyaluminium chloride and aluminium sulphate) and reduce turbidity and suspended solids in the water, achieving comparable results to traditional chemical coagulants while eliminating the use of toxic and corrosive substances.
The project encountered some difficulties in achieving certification of nature-based coagulants. This certification was crucial for the real-scale implementation of the technology in DWTP. The certification process revealed undesirable levels of amine in the treated water, which exceeded the acceptable limits. As a result, the real-scale implementation of the technology was canceled, and the project had to focus on pilot-scale validation instead.
One of the key achievements of the project was the successful adaptation and optimisation of semi-industrial and pilot-scale production reactors for the natural coagulants. The project team fine-tuned the production process to ensure the coagulants' stability and efficiency, resulting in a product that could be used in various water treatment scenarios.
The pilot tests conducted in Valencia and Madrid provided valuable insights into the effectiveness of the natural coagulants. In Valencia, the tests showed that the natural coagulants could achieve a significant reduction in turbidity by 66.1% to 75.3% and suspended solids by 88.0% to 92.5%, while also completely removing aluminium content from the water. The tests in Madrid further confirmed these findings, demonstrating that the natural coagulants could perform effectively under different water treatment conditions. Additionally, the tests highlighted the potential environmental benefits of using natural coagulants, such as the reduction of hazardous chemical usage and the potential for safer sludge management. The project demonstrated that the natural coagulants could achieve similar or better performance in water treatment compared to traditional coagulants, with the added advantage of being environmentally friendly.
The project also produced a detailed business plan and market analysis, identifying key stakeholders and potential markets for the natural coagulants. These efforts aimed to ensure the long-term sustainability and commercial viability of the project outcomes.
Some remarkable outcomes generated by the project include:
- the successful replacement of 100% of dangerous polyaluminium chloride and aluminium sulphate with natural-based coagulants in the pilot plant implementation. This chemical substitution resulted in replacing 758 Tm of polyaluminum chloride and 1 662 Tm of aluminium sulphate annually in real-scale operations;
- the achievement of a turbidity reduction from the natural coagulants of over 75% at a dosage of 10 ppm, compared to polyaluminum chloride which required 20 ppm for similar results;
- the achievement of a suspended solids removal rate of 88.0% to 92.5% thanks to the natural coagulants;
- the elimination of the need for toxic and corrosive substances in the use of natural coagulants during pilot tests , reducing the environmental impact;
- cost savings, despite the higher cost of natural coagulants (EUR 678/Tm) compared to polyaluminum chloride (EUR 330/Tm) and aluminum sulphate (EUR 200/Tm). The estimated overall cost per cubic meter of treated water would be similar or slightly higher. Significant cost savings were achieved in additional products consumption, raw materials delivery, and containers management;
- reduction in sludge production, that lead to decreased management costs. For example, in the La Presa plant, the sludge production would be reduced from 1 700 Tn/year to 1 496 Tn/year, resulting in a cost saving of EUR 5 508 per year;
- reduction in the cost of raw materials delivery by EUR 15 657 per year in the La Presa plant and by EUR 210 060 per year in the Colmenar plant;
- adaptation and optimisation of semi-industrial and pilot-scale production reactors for the natural coagulants;
- similar or better performance of the natural coagulants in water treatment compared to traditional coagulants, with the added advantage of being environmentally friendly.
