Utilizing the Bullhead
for Sludge Management
In the early 1990's, the Vermont
Department of Environmental Conservation became aware of the work that was being
done by Terry Welch at the Bethlehem, New Hampshire wastewater treatment plant.
Terry was attempting to incorporate as many natural control systems into his
lagoons as possible, not just bullhead but also crayfish, Daphnia for algae
control, even bladderwort for Daphnia control. The introduction of hundreds of
bullhead into his ponds did significantly reduce the large accumulation of
sludge on the lagoon floors. Since the removal of sludge is a major expense for
the small municipalities that typically own aerated lagoons in Vermont, we felt
it would be worthwhile to investigate this "natural" treatment.
In the spring of 1994, Paul Olander worked with John Hall, John Claussen, and Rich Kern to capture some of the 165 adult bullhead in Baker Pond and move them to treatment lagoons at the Royalton WWTF. The Royalton was chosen because they had significant sludge deposits in all three cells and needed to do a sludge removal but the town did not have sufficient money. We stocked most in the last pond, some in the middle pond, and a few in the first pond. We had done a significant amount of baseline data gathering and continued to gather data through the summer and fall. What we saw was a complete reduction of the 10" of sludge in the third cell and a decrease in the second cell. There was some evidence that some of the sludge went out in the effluent as a slightly higher Total Suspended Solids, but the effluent was well within permit limitations. There also seemed to be an increase in algae in the cells. The following spring the bullheads died during the spring benthal release ( probably due to ammonia from the increased anaerobic activity in winter deposited sludge). The fish that were 10" in length the previous year were running in the rage of 13 to 14 inches with massive heads. Minks, raccoons, eagles, and gulls were observed picking up the fish.
The conclusions drawn were that the fish did seem to reduce the sludge accumulations, but that heavy deposits would release ammonia in the spring and up to 30 mg/l concentrations were found at times. Conclusions were drawn to the fact that ponds with heavy accumulations of sludge may not support the survival of the fish. The mechanism for sludge reduction appeared to be that the fish, on feeding on aquatic insect larvae in the sludge, were rolling the sludge into the upper layers of the aerobic zone. Further stabilization takes place there, and some "ash" goes back to the bottom or out in the effluent.
The feeling was the fish did not have a serious deleterious effect on effluent quality and probably would aid in reducing the frequency of cleanouts even though the fish may not survive the spring release well. VTDC staff advised operators considering the use of fish that their use would be permittee, but that the operators must seek permission from their District Fisheries Biologists.
Some facilities did try stalking bullhead, most seeking permission first. Plant specifics follow. The results seem to be inline with conclusions made by the VTDC staff, and that the chief benefit of socking bullheads would be reduction of sludge handling costs. Removal of sludge from the Hardwick WWTF cost about $90,000. In a recent survey of plants, many of the operators expressed a strong interest in stalking bullhead if the F & W Department resumes the granting of letters of authorization.
Bullhead-Stocked Wastewater Plants Specifics
Brighton ( Island Pond ) - A previous operator put in about 200 adult fish from a local pond in 1997. This level of stocking has been continuous every year. The sludge depths have been stable during the period of time. No reproduction has been seen, but herons do fish the ponds regularly now.
Jeffersonville - Stocked about 100 fish in each of 2 cells two years ago. The operator noticed that herons began to be seen frequently around the ponds. There has been no evidence of the fish this past year. The overall sludge depth appears to have been reduced by 3 inches, and more aeration was necessary, and the T.S.S. was up in the effluent indicating sludge to the overlying water column.
Manchester - Bullhead were observed gulping air in the second lagoon in the late 1980's. Apparently some bullhead were dumped in soon after the ponds were built. The operators have not done any formal stocking. The fish are reproducing and all different sizes have been found dead in the chlorine contact chamber. Most of the fish appear to be in the second cell according to the operators. That cell has never been cleaned and the sludge depth appears to be steady. The first cell was cleaned in 1991 and the depths show a slight increase every year.
South Royalton - After the loss of the 165 adults, the next year the operator added about 700 bullhead ranging from 2 to 6 inches. These were taken from a private pond that was being drawn down to get rid of the trash fish. Last year some dead fish were in the 12 to 14 inch range and some larger live ones have been seen. No fry have ever been observed.
Smugglers Notch - This private, non-discharging system had stocked fish since 1995. The fish were lost during an upgrade project on the lagoons last year. About 200 pounds of 3/4 pound fish were added to the 1.2 million gallon first cell the next year. They have been observed as surviving from year to year and can be seen "gulping" at the surface in the evenings. Sludge was removed from this heavily pond in 1990 and since the fish were added the sludge depths have been stable.
Waterbury - In 1995 the operators began adding a few fish per year to the lagoons. Last spring some 1,500 -2,000 adult bullheads in the size range of 8 to 12 inches were added mostly to the first of the three cells. Another 1,000 were added early this spring. Half were placed into the first cell and half into the other 2 cells. There is much evidence of live fish and reproduction. The operator has seen three class sizes: fry, 5-6 inch and adults. They have been observed feeding in the algae and duckweed rafts as well as the sludge mats most notably in the evenings.