An aspergillium is another name for an aspergillum, an implement in the form of a brush for the sprinkling of holy water.
Depends; if we're talking about the Holy Water in the fonts (the ones you use to bless yourself when entering/exiting the Nave) and Baptismal Font then it is left their. Holy Water that is in the aspergillium (Holy Water sprinkler), aspersorium (Bucket for the aspergillium), and the water used for ablutions (Priest's washing of hands) is probably poured into the Baptismal Font or down the Sacrarium (special sink that leads directly to the ground that is used for cleaning anything that came into contact with the Eucharist). A lot of parishes also have tin spigot-like containers with Holy Water in it for parishioners to take home for personal use; The Holy Water is also left in these containers. Now, if the Holy Water becomes gunky or suffers stagnation, it is poured down the Sacrarium and new water is blessed by the parish Priest.
Biological contamination occurs when foods containing naturally occurring substances that are poisonous to humans are ingested; such solanine in green potatoes, oxalic acid in the leaves of rhubarb and some type of mushrooms.