The Masthuggskajen area in Gothenburg is undergoing transformation - from extensive parking areas and roads to new residences and premises with walking and cycling paths. LPE Sweden AB is involved in the area, excavating and remediating a site where offices and apartments will be built in the future.

The site previously housed parking spaces and a gas station. Also, the ground had been filled with materials originating from various unknown places - so it was unclear what substances were present in the soil.

As the excavation went below the groundwater level, water accumulated in the pit. Upon sampling, this water turned out to be contaminated with particle concentrations exceeding permissible levels. LPE Sweden AB constructed pump pits and lined secure shafts for interim storage and sedimentation. However, to prevent discharging contaminated water into the drainage network, the company needed additional measures.

–The contaminated water emerged during the course of the work. That's when I contacted Swedish Hydro Solutions, which had a short delivery time and could quickly be on-site with a facility, says Richard Eriksson, site manager at LPE Sweden.

Fine-Tuned Treatment Process

To remove particles, Swedish Hydro Solutions promptly set up a treatment facility with a capacity of 10 cubic meters of water per hour, consisting of pH regulation, a container with dosing equipment primarily for chitosan, and a sedimentation tank.

For optimal flocculation, Swedish Hydro Solutions adapted the flocculation process to the site's conditions - there is a difference in clay particles depending on their chemical composition.

– We want the particles to flocculate so that they become heavy and sink. It's a craft that requires finesse, where we observe how flocculation occurs at the specific site, so that we can then find the right level, says Erik Tholén, project manager at Swedish Hydro Solutions.

At Masthuggskajen, there were some particles in the excavation water that weren’t electrically charged – and therefor did not react to chitosan.

– In such cases, we use complementary agents that, in combination with chitosan, create effective flocculation and optimal treatment results.

Easy-to-Manage Facility

After the facility was installed, Swedish Hydro Solutions was on-site approximately every other week to perform maintenance and calibration of the equipment. LPE Sweden managed the daily inspection, taking about 15 minutes, on their own.

– They gave us an overview and showed where everything is. It was quite clear how to proceed. It's an easy-to-manage facility, says Richard Eriksson.

The treated water came from a large area with several smaller water accumulations, where some of the pits were filled with occasionally almost black water. However, after chitosan treatment and sedimentation, clear water emerged, meeting the supervisory authority's requirements with ease.

– The water treatment has worked well. Swedish Hydro Solutions uses different methods than others on the market. But tests after treatment have not shown any contaminants, so it has fulfilled its purpose, says Richard Eriksson.

Swedish Hydro Solutions was on-site with a facility for approximately four months, from June to October 2021.