OPERATIONAL CONTROL STRATEGIES FOR SNAIL INFESTATION IN TRICKLING FILTER FACILITIES

Trickling filters (TFs) are an ideal habitat for a diverse microbial community enriched with animals, or fauna. These fauna may have a beneficial impact on carbon-oxidizing TF bioreactor performance, but only when they exist in the proper balance. An infestation, however, can be detrimental to several aspects of TF-based wastewater treatment plants (WWTPs). Therefore, state-of-the-art TF-process design incorporates mechanisms to manage macro fauna accumulation and/or development. Snail infestation is a common TF operational issue that can degrade effluent quality, adversely impact biosolids handling infrastructure, and be detrimental to costly process mechanical equipment. Snails, from a process perspective, have the most profound detrimental impact on process performance because of (a) nitrifying biofilm grazing; (b) process mechanical equipment damage due to snail shells, (c) excess biochemical oxygen demand exerted by snail carcasses, and (d) increased suspended solids measurements owing to snail shells and bodies. There is a paucity of information in the environmental engineering literature detailing the production rate of higher life-form predators, such as snails, in the TF process. Therefore, it follows that there is little gauge for the effectiveness of snail minimization, or removal, techniques. Generally, only case specific studies related to substrate transformation reaction rates or fauna mass weight measurement methods have been used to quantify macro fauna production. The present study (a) describes macro fauna that are commonly found in TFs treating municipal wastewater, (b) surveys state-of-the-art snail removal technologies and their reported effectiveness, (c) identifies protocol for implementing various snail removal techniques, and (d) means for creating a database that can be used to establish snail production and removal in TF-based WWTPs.