Fall 2009 Closure

**Q. On the slide in the Chemical Treatment slideshow of the solubility of copper:  at pH 9 copper is at its lowest solubility; does that mean that any copper in a fluid stream at pH 9 would be precipitating out and could be removed by filters?  Or does it mean that at pH 9 there is the least amount of copper leaching from copper tubing into a fluid that is passing through it?
A. The solubility at pH 9 is 0.001 mg/L , which is essentially insoluble.  So if you put 100 mg of Cu in water with a pH of 6, these would be atoms, not ions, all would be dissolved, and be in suspension as free atoms or (I’m not sure) tiny agglomeration of atoms.   Now if you added base, say sodium hydroxide, until the pH was 9, all but a tiny amount of the Cu would form crystals of Cu metal and sink to the bottom.  However, we didn’t say how fast this would happen.  It could happen quickly or take some time.   For precipitation to be useful, it would need to be quick, but that rate is something you could look up or test in the lab.  Your question about copper pipe then, also relates to rate.  If the pipe held water with a pH very different than 9, it would tend to dissolve the pipe.  But how long would that take?  Perhaps a long time or not – again, you can look up suitability of materials for piping various fluids.  Copper is fairly reactive and not used for most chemical piping. 

**Q. I am confused on the chlorine exhaust. The slide said a lot are produced. Are these emissions from things that should not have been incinerated in the first place?
A. There is a lot of chloride in municipal solid waste from salt – and that is not a problem that I know of.  The ion is completely reduced and not much goes on with it. The potential problem comes from covalently bound chlorine and aromatic compounds, such as many plastics, and contaminants such as PCB.  Under heat and poor oxygen, a small portion of these can be converted to various chlorinated dioxins and such, some of which are very toxic.  So, it would be better not to burn these plastics, or burn them with excess oxygen.  It is very difficult to control the burning of MSW, because it is so heterogeneous, and excess air reduces both the temperature and retention time.  On the other hand, with good management, the emissions of the baddies tends to be very small and probably insignificant. 

Closure, 2007

**Q. What to do with the ash produced in incineration was a little foggy to me.  If the ash contains hevy metals what is done with it at that point?
A.  If the ash does not pass the TCLP, it could not be placed in a MSW dump.  It would be quite realistic, that regular waste could pass the TCLP but its ash not pass.  The permitting of incinerators is quite difficult and details and surely the ash disposal would be an important permit issue.

**Q. I realize some take a great deal of time to carry out, for example phytoremediation can take years to clean up a site.  Are most sites able to carry out this type of cleanup process, or are more expedient methods generally used?  I guess is phyto and bioremediation more or less specialized for sites that can deal with the longer clean up time? 
A. That depends on who is responsible for the clean up and what they are permitted to do.  Owners will always opt for “natural attenuation,” then phyto or bio remediaton, because they are the cheapest.  Most CERCLA cleanups are the result of a negotiated settlement or a court order.  That will ultimately determine how the mess is handled.  Keep in mind that the first step is almost always “source removal,” that is, the leaking drums.  All the other methods usually are used for the residual contamination.

* Q. One thing I often struggle with is the by-products or wastes that can be generated from using come of these technologies.  Sometimes you can concentrate the waste so that now you have RCRA issues.  The previous media wasn't RCRA hazardous (i.e. heavy metals) but are difficult to get to.  Following some remediation they are concentrated but now you have a RCRA problem.  I guess this is just an additional criterion to be evaluated when selecting the most appropriate remedy.
A. My favorite is the air stripping tower that converts water pollution to air pollution.  Many technologies change the form of the hazard to something more manageable.  Sometimes it is political – “look we are doing something about it.”  Money is often the limiting factor.

*Q. I was curious about the thermal processes in regards to the new global warming focus on CO2 emissions.  Generating those high temps must take substantial amounts of fuel and are there any pressures that you know of being applied now that anything that burns is being scrutinized more heavily?  Will this lead to less thermal processes?
A. It would be hard to lead to less thermal, since it is almost impossible to get any new incinerators permitted and that has been true for many years, long before the current global warming scare.
 http://www.faculty.uaf.edu/ffrap/Presentations/Climate_change.html