project

Application of electrocoagulation to water with low conductivity

The wastewater and drinking water sector in the Netherlands and Europe is committed to reducing its CO2 footprint. This also includes a desire to reduce the use of chemicals. During drinking water production, an iron flocculant can be dosed into the water to remove turbidity, phosphorus, NOM and arsenic, and to treat backwash water. Electrocoagulation offers a promising alternative to this chemical coagulation, thanks to its CO2 footprint and high coagulation efficiency; moreover, it reduces flocculant transport and storage. It is still unknown whether successful application in drinking water sources (in the Netherlands) is achieved with specific targets such as suspended solids, turbidity, and TOC removale.

This pilot study investigates the applicability of electrocoagulation for treating surface water and sand filter backwash water with relatively low conductivity (≤600 μS/cm) in comparison to conventional coagulation (FeCl3 dosage).

Approach

This project assessed electrocoagulation through pilot testing, Life Cycle Assessment (LCA), and cost analysis (CAPEX and OPEX). Pilot at Dunea’s Bergambacht plant tested 1m3 batches of surface and sand filter backwash water, monitoring water quality parameters like pH, turbidity, color, arsenic, suspended solids and phosphates. Investment and operational costs were calculated using expert workshops and cost calculation tools. The LCA, following ISO 14040/44 standards, compared electrocoagulation and conventional iron chloride coagulation using SimaPro software and Ecoinvent data, focusing on Ecopoints and CO2 emissions to assess electrocoagulation’s potential.

Image 1. Flocculation units during the pilot test at Dunea. Right: containerized pilot and feed tank.

Results and conclusions

Electrocoagulation offers comparable removal efficiencies to conventional coagulation but requires higher iron dosages. For sand filter backwash water, EC achieved 80% arsenic, 75% suspended solids, 86% phosphorus, 43% organic carbon, 56% turbidity, and 48% color removal, improving further after settling. However, it has significantly higher investment costs and operational costs, driven primarily by electricity consumption (due to higher iron dosage).

Environmental assessments revealed mixed impacts: conventional coagulation has higher resource use, acidification, and eutrophication due to chemical inputs, while electrocoagulation has greater climate impacts due to high electricity use with the pilot’s reactor configuration. Transitioning to renewable energy could cut electrocoagulation’s environmental impacts by 64-80%, and optimizing iron dosage would further reduce energy demands. Sensitivity analysis suggests electrocoagulation economic and environmental performance depends heavily on energy efficiency and sourcing, with the potential for significant improvements through targeted optimizations.

Applicability and relevance

Electrocoagulation achieves comparable removal efficiencies to conventional coagulation but requires higher iron dosages, increasing costs and energy demands. Critical factors include energy efficiency (kg Fe/KWh), electrode configuration design, and energy prices. For conventional drinking water treatment, optimizing electrocoagulation to match coagulation’s iron dosages and addressing low water conductivity challenges is essential for viability.

Partners and collaboration

The project ‘Application of electrocoagulation on water with low conductivity’ was developed with the following partners: Brabant Water, De Watergroep, Dunea, QStone Capital and KWR.