52    A STUDY INTO THE EFFECT OF A SERIES OF SHOCKS ON
A PILOT-SCALE ANAEROBIC FILTER
M. E. Caine, Senior Research Associate
G. K. Anderson, Senior Lecturer
T. Donnelly, Research Associate
Department of Civil Engineering
University of Newcastle upon Tyne
Newcastle upon Tyne
United Kingdom NE1 7RU
INTRODUCTION
The imposition of more stringent industrial consents to discharge led to companies examining the
potential of in-house treatment.' Of the options available, high rate anaerobic digestion processes
such as the Anaerobic Filter2 and the UASB3 have inherent advantages over both aerobic and
physical/chemical techniques. These include: low operating costs, low sludge yield and the production
of a high grade fuel gas.
Scepticism has resulted in inertia within process industries when considering anaerobic digestion.
Doubts have been based on several factors: (i) the poor performance of many full-scale UASBs of
crude design treating non-saccharide waste, (ii) the apparent lack of comprehensive process control,
(iii) the time needed to develop the required concentration of biomass at a startup and (iv), the
resistance of a "sensitive" biological process to accidental shocks.
Careful process selection and the employment of skilled operators will overcome (i) and (ii).
However the consequence of reactor failure following severe shock is usually reseeding and restart.
This is very expensive in terms of time and seed sludge. The possibility of litigation also arises.
This study was designed to show the effect of a series of severe shocks (pH, temperature, organic
and hydraulic) on a pilot-scale Anaerobic Filter, (AF), operating on a dairy effluent. Effluent quality,
gas production and process stability were monitored throughout an eight hour shock period and for a
further sixteen hours. The relationship between the above were discussed.
MATERIALS AND METHODS
Description of Process
The study was carried out at the SERC anaerobic digestion facility based on-site at Birds-Eye Walls
in Gloucester. The facility comprised a 13 m3 balance tank supplying four reactors: Anaerobic Filter,
UASB, Contact Process (all nominally 5m3) and an Expanded Bed (0.5m3). The actual liquid volume
of the Anaerobic Filter was 5.28 m3. The media (a variety of Pall ring with A:V ratio 160m2:m3) were
contained in two 1.64 m3 compartments 1.5 m above the base of the reactor. The balance tank and
Anaerobic Filter are illustrated in Figure 1.
Composition of Wastewater
The wastewater was produced by mixing ice cream and water-ice products to a target COD of 6000
mg l1. The two main CIP (cleaning in place) detergents were also added at the concentrations found
in the factory wastewater. This accurately represented an ice-cream factory effluent. The balance tank
pH was maintained automatically between 6.60 and 6.80 using sodium hydroxide. Nutrients, N and
P04 (dosed at COD:N:P04, 100:2:1) and chelated trace elements (Fe,Mn,Co,Ni dosed at 0.02 mg 1"'
metal) were added manually. The physical and chemical characteristics of the raw wastewater during
steady state prior to the shock study are given in Table 1.
45lh Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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