Wednesday, May 13, 2015

Woman and Husband Declare War on Black Mud

I's just hoping most of the awfulness of this article is bad reporting and not bad science, but I'm just not sure:

Husband-and-wife scientists take on black muck clogging Chesapeake Bay
Imagine a vast septic tank that was continuously filled for 200 years without ever being cleaned out. This tank contains an enormous volume of smelly, black gunk — up to 12 feet deep in some spots — that harbors harmful bacteria and suffocates most life-forms.

Welcome to the creeks of Chesapeake Bay.

Decades of work by organizations such as the Chesapeake Bay Foundation and by government agencies have dramatically reduced the amount of pollution entering the bay through its tributaries. But the Chesapeake is still clogged with millions of tons of slimy black muck — full of harmful ammonia and phosphates — that foils attempts to restore water quality and diversity of life.

A husband-and-wife science team is trying to find a way to destroy the muck, and their hoped-for solution lies at the bottom of a septic tank.

Diana Muller, director of scientific monitoring at the South River Federation in Edgewater, Md., and Andrew Muller, a professor of oceanography at the U.S. Naval Academy in Annapolis, are exploring whether a sort of dietary supplement for septic systems can digest black muck from the creeks that feed the Chesapeake.

They are using a formula similar to that of Rid-X, a blend of bacteria and enzymes that digests the sludge that builds up in septic systems over time. The bacteria include two types of microbes, nitrosomonas and nitrobacter. Nitrosomonas oxidizes otherwise harmful ammonia (plentiful in the Chesapeake’s black muck) into nitrites; then the nitrobacter converts those nitrites into nitrates, which aquatic grasses and other plants can use for growth.
Black (stinky) mud is found in marine (or even slightly salty estuaries) wherever decomposition rates organic inputs from algae and terrestrial sources (fallen leaves are shocking important in this) exceed the ability of oxygen to diffuse into the sediments, and allow for aerobic respiration of the organic carbon.  The black itself is iron sulfide formed when sulfate, a very common ion in seawater, is respired by sulfate reducing bacteria as they use the organic carbon. There is a sequence of reactions that take place in sediment as successive electron acceptors are used up (Oxygen is an electron acceptor, becoming water). Here:

Source: Alfred Wegener Insitut
If the mud is black, it's getting too much organic material, and not enough oxygen. It's a pretty safe bet that along the way, bacteria are operating at about as fast a rate they can, given the conditions, and available materials.  If not, they'll be replaced by bacteria that can.

How do you fix it?  Well, you could add oxygen, which is easy on the small scale (bubble it, like an aquarium) but much more difficult on the Bay or even tributary scale. But back to the study:
The black muck does indeed appear to be disappearing from two of three 40-gallon tanks of water and mud in a lab at the Naval Academy. Tank 1 serves as a control against which the others can be compared. Tank 2 has tubes that provide aeration through the bottom of the mud. Tank 3 is receiving both aeration and large amounts of helpful bacteria.

Preliminary data gathered daily by Midshipman Annie Folkie of Charlottesville, Va., indicate that by at least one measure, the combination of aeration and bacteria is working. Four months into the study, Tank 3 has less than half of the harmful phosphates per liter than the control tank has. Tank 2 isn’t far behind Tank 3.
Really, oxygen helped a lot? I'm shocked, shocked. I'm a little surprised they are seeing an added response to added bacteria and all, but I suppose they could contain some vitamins or something in low supply in the mud.

I really hope they have a better level of replication than one tank of each treatment. 5 would be outstanding, 2 a bare minimum, and 3 a reasonable compromise between level of effort and expected difference between the treatments.

Under no circumstance should a single tank per treatment be used. There are no valid statistics. But you can tell a story, they way they have here.

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