Prevention of well clogging during aquifer storage of turbid tile drainage water rich in dissolved organic carbon and nutrients

Well clogging was studied at an aquifer storage transfer and recovery (ASTR) site used to secure freshwater supply for a flower bulb farm. Tile drainage water (TDW) was collected from a 10-ha parcel, stored in a sandy brackish coastal aquifer via well injection in wet periods, and reused during dry periods. This ASTR application has been susceptible to clogging, as the TDW composition largely exceeded most clogging mitigation guidelines. TDW pretreatment by sand filtration did not cause substantial clogging at a smaller ASR site (2 ha) at the same farm. In the current (10 ha) system, sand filtration was substituted by 40-mu m disc filters to lower costs (by 10,000-30,000 Euro) and reduce space (by 50-100 m(2)). This measure treated TDW insufficiently and injection wells rapidly clogged. Chemical, biological, and physical clogging occurred, as observed from elemental, organic carbon, 16S rRNA, and grain-size distribution analyses of the clogging material. Physical clogging by particles was the main cause, based on the strong relation between injected turbidity load and normalized well injectivity. Periodical backflushing of injection wells improved operation, although the disc filters clogged when the turbidity increased (up to 165 NTU) during a severe rainfall event (44 mm in 3 days). Automated periodical backflushing, together with regulating the maximum turbidity (<20 NTU) of the TDW, protected ASTR operation, but reduced the injected TDW volume by similar to 20-25%. The studied clogging-prevention measures collectively are only viable as an alternative for sand filtration when the injected volume remains sufficient to secure the farmer's needs for irrigation.

Automated summary

This study examines well clogging in an aquifer storage transfer and recovery (ASTR) system used for securing freshwater supply for a flower bulb farm. The system faced clogging issues due to the composition of the collected tile drainage water (TDW) exceeding clogging mitigation guidelines. Substituting sand filtration with disc filters led to insufficient treatment and rapid clogging of injection wells. Physical clogging by particles was identified as the main cause, and measures such as periodical backflushing and regulating maximum turbidity protected ASTR operation but reduced injected TDW volume.