Cleanout of a Plug-Flow Anaerobic Digester after Five Years of Continuous Operation

Several plug-flow anaerobic digesters have been constructed on dairy farms in New York State in recent years primarily for odor control and also for combined heat and power generation. One long-term concern with these systems is the accumulation of non-digestible solids in the digestion cell. Non-digestible solids, made up of fixed solids and/or non-biologically degradable volatile solids can enter a manure treatment system; typical sources include manure, animal feed, bedding, and stones and sand tracked in by equipment tires. Typically an anaerobic digester (AD) is designed for a target daily loading rate and hydraulic retention time (HRT). If a significant portion fills with non-digestible materials over time and lowers the HRT, biogas production may be reduced and the digester may not perform as desired. A mesophilic plug-flow anaerobic digester in New York State was temporarily decommissioned in March of 2006 to perform emergency repairs to the internal heating system. This untimely need for repair provided an opportunity to extensively analyze the digester contents, both immediately after removing the flexible membrane cover in an undisturbed state and also during the cleanout process

“Anting” in Blue Jays: evidence in support of a food-preparatory function

Anting, the plumage-dipping behavior to which ants (mostly formicines) are commonly subjected by birds (mostly passerines), is shown in tests with hand-raised Blue Jays (Cyanocitta cristata) and the ant Formica exsectoides to be instinctive: the birds displayed typical renditions of the behavior on the first occasion that they encountered ants. Evidence is presented supportive of the view that anting is a strategy by which birds render ants fit for ingestion. Formicine ants are ordinarily protected by their formic acid-containing spray. Being wiped into the bird’s plumage causes them to discharge that spray, without harm to the bird, to the point of almost total emptying of the glandular sac in which the secretion is stored. The ants are therefore essentially secretion-free by the time they are swallowed. Further evidence indicates that it is the ant’s possession of the acid sac that triggers the anting behavior in the bird. If F. exsectoides are surgically deprived of their acid sac, they are eaten by the birds without first being subjected to anting. Data are also presented indicating that the ant’s crop, which is especially capacious in formicines (its contents may amount to over 30% of the formicine’s mass), and which appears to survive the anting procedure intact, constitutes, at least when laden, a valuable component of the trophic package that the bird accesses by anting

Chemical defense: Aquatic beetle ( <i>Dineutes hornii</i> ) vs. fish ( <i>Micropterus salmoides</i> )

Captive largemouth bass ( Micropterus salmoides ) reject the gyrinid beetle, Dineutes hornii. They also reject edible items (mealworms) treated by topical addition of the norsesquiterpene gyrinidal, the principal component of the defensive secretion of the beetle. The bass' oral tolerance of gyrinidal varies broadly as a function of the gyrinidal dosage and the state of satiation of the fish. When taking a D. hornii or a gyrinidal-treated mealworm in the mouth, the fish subjects the item to an intensive oral flushing behavior, seemingly intended to rid the item of gyrinidal. The duration of oral flushing is itself a function of the gyrinidal dosage and the state of satiation of the bass. To counter oral flushing, D. hornii emits its secretion as a slow trickle. Duration of emission is slightly longer (1.5 min) than the time (1.3 min) invested by the bass in flushing a D. hornii before rejecting the beetle. We postulate that flush resistance may be a general feature of defensive chemical delivery systems in aquatic prey, given that oral flushing may be a common strategy of fish. </jats:p