Passability of Chironomid Larvae in Granular Activated Carbon

Abstract

We conducted an experiment to confirm the passability of chironomid larvae (Glyptotendipes tokunagai) in granular activated carbon (GAC) used in water treatment plants. After injecting larvae at different growth stages (first through fourth instars) into circular columns filled with GAC, the number of individuals and their locations within the GAC columns were recorded after 168 h. We found that more than 80% of the injected larvae in the first instar and 3.3% in the second instar passed, whereas none from the third and fourth instars had passed through the column. The second instar larvae were evenly distributed within the column, whereas the third and fourth instar larvae were mostly distributed within 10 cm of the upper layer of the GAC. Our results demonstrate the passability of chironomid larvae in GAC and can be used as basic information for water quality management in water treatment plants.

Comprehensive Solutions to Prevent Larvae Breakout in Water Filtration Systems

“…It was particularly notable that the larvae breakout was in their early developmental stages, specifically instar 1 and instar 2. This finding aligns with previous studies that have shown limited effectiveness of GAC columns in removing larvae from treated water [26]. In the case of the sand filter, the effective size (ES) of the sand particles and the uniformity coefficient (UC) played a crucial role.…”

“…As organisms typically demand more energy as they mature, fourth-stage instar larvae likely had higher energy needs compared with earlier instar larvae. Consequently, a greater occurrence of cannibalism was observed during the fourth instar stage [26,38].…”

“…The high number of third-and fourth-stage instar larvae observed during the backwash process can be attributed to the behavior of these stages, as they tend to dig and occupy only the top 10 cm of the filter media. This shallow position makes them more susceptible to being flushed out during the backwash [26,43]. The proper backwash procedure consists of multiple steps, each serving a specific purpose in the cleaning and maintenance of the filtration system.…”

Assessing the Efficacy of Coagulation (Al3+) and Chlorination in Water Treatment Plant Processes: Inactivating Chironomid Larvae for Improved Tap Water Quality

“…Recently, the detection of macroinvertebrates, specifically chironomid larvae, in tap water supplied by Korean water treatment facilities in July 2020 has prompted apprehension. A nationwide investigation that ensued following the initial discovery revealed that chironomid larvae were present in seven out of the 49 sites inspected [4]. The presence of these organisms in the water supply suggests that there may be issues with the water treatment process, as larvae can easily penetrate sand filters and end up in waterworks reservoirs [5].…”