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Tungsten in solution may exist as a wide variety of species depending on concentration, pH,
and aging time. Despite a substantial number of studies on this topic, the speciation of
tungsten in aqueous solutions is still not completely understood. To address issues of fate,
transport and potential bioavailability, it is necessary to be able to assess the speciation of
tungsten in environmental systems. This study investigates the use of Laser
Desorption/Ionization mass spectrometry combined with a Time-of-Flight mass analyzer (LDITOF)
as well as Raman spectroscopy as potential techniques in speciation studies. Raman
spectroscopy has been successful in identifying the dominant species under a narrow range
of conditions. The ultimate goal is to extend the range of conditions and concentrations while
also identifying subordinate species.

A mathematical model to simulate microbial growth and lag time is proposed in the present
work in accordance with Sengor et al. (2009). The model is verified experimentally for a mixed
microbial culture growing at metal free and at Cr(III) or Cr(VI) contaminated environments.
The model is further verified using a monoculture of Pseudomonas sp. growing at metal free
and Zn(II) contaminated environment. The effect of temperature on microbial growth and lag
is also simulated by the model. The simulation results show for the mixed culture that growth
rate decrease with parallel increase in lag time, with the rise of either Cr(III) or Cr(VI)
concentration. For Pseudomonas sp., the simulation indicated that there is almost nil lag time
for growth at 35 ºC, while approximately 10 h lag time is calculated for growth at ambient
temperature (20 ºC). The lag time increases by approximately 6 more hours when 0.01 mM
Zn(II) is added in the growth medium (at ambient temperature). The increase of lag time with
temperature reduction is explained by the fact that the biochemical reactions are slowed down
at lower temperatures. A good correlation between model predictions and simulation results is
observed.

Lead (Pb) particles that detach from the plumbing and contaminate drinking water can pose a
significant health threat, which is often underestimated. Laboratory simulation of this problem
revealed that standard quantification protocols in the US may miss 80% of the lead present in
the water. At the same time, a significant fraction of this undetected particulate lead may be
bioavailable when ingested. A critical review of the Washington DC lead-in-water crisis
suggested that lead in water might constitute a greater public health risk than generally
acknowledged, in at least some circumstances. It also revealed deficiencies in the public
health response as well as in alerting the public to elevated levels of lead, and the subject
continues to be mired in controversy. Our independent testing at six Washington DC public
schools in 2008 showed that problems with elevated lead still persist at 2-41% of taps
sampled at each school, even after remedial measures were implemented.

The efficiency of TiO2 photocatalysis induced by ultraviolet and visible irradiation and salt-free
electrolysis over boron-doped diamond electrodes to inactivate total (TC) and fecal (FC)
coliforms in secondary treated municipal wastewater was evaluated. Photocatalytic
experiments were conducted with two types of titania (Degussa P25 and sulfur-doped
catalyst) at loadings in the range 0.1-0.5 g l-1 and three types of irradiation, i.e. artificial UV-A,
artificial visible and solar. Electrolysis was conducted in a flow-through cell at anodic current
densities of 14.3 and 28.6 mA cm-2 without the addition of auxiliary chemicals. Inactivation
followed a first-order kinetic expression with regard to bacteria population and the rate was
dependent of the experimental conditions in question. In general, electrochemical disinfection
was up to about two orders of magnitude faster than photocatalysis; for instance, TC
population decreased to less than 5% of the initial population after 9 and 4 min at 14.3 mA
cm-2 and 28.6 mA cm-2 respectively. Similar efficiencies with TiO2 photocatalysis would
require at least 30 min of contact time. Interestingly, energy consumption for the
electrochemical process was computed to about 0.5 kWh per m3 of treated effluent, well
below the respective value for photocatalysis.