nutrients have a long-lasting stay in soil
Phosphorus and other minerals from land-applied
biosolids can remain in the soil for many years, according to research by Eton
Codling, Agricultural Research Service agronomist.
Codling has been
investigating how long plant-available phosphorus and other minerals from
biosolids stay in soil and how much phosphorus, copper, cadmium, lead,
manganese, and zinc is taken up by wheat growing in this soil, according to the
article “The Real Dirt on Biosolids as Soil Amendments” that appeared in the
January 2013 issue of Agricultural Research magazine.
Monitoring minerals in soil
Codling monitored mineral levels of soil
that had received a single amendment of biosolids, which had been processed by
either heat, lime addition, anaerobic digestion, or air drying. The biosolids
had been added to the soil during another study 16 to 24 years prior to
Codling’s research project. Overall, he observed higher levels of phosphorus,
cadmium, copper, and zinc in the biosolids-amended soil than the control soil,
the article says.
Codling also found
that phosphorus solubility in soil varied with the process used to treat the
biosolids and the amount of biosolids applied. Soil with heat-treated biosolids
contained higher levels of soluble phosphorus than soil amended with
lime-treated biosolids, even in soil that received three times more
lime-treated biosolids. This occurred because lime-treated biosolids
sequestered phosphorus in low-solubility calcium phosphate compounds, the
Examining the effects on wheat
another study examining wheat grown in pots containing each type of amended
soil. He found that wheat yields often were higher in soils amended with
biosolids than wheat grown in control soil. The highest yields came from soil
containing biosolids processed by anaerobic digestion. Yields were reduced in
soils with lime-treated biosolids; this likely was due to manganese deficiency,
the article says.
During this study,
Codling also measured accumulated mineral levels in the above-ground biomass.
Wheat grown in any of the biosolids-amended soils had higher phosphorus
concentrations than wheat grown in control soils, coinciding with elevated
levels of plant-available phosphorus in the soil.
Because soil mineral levels were reduced
after harvesting one wheat crop, and all material leaching from the pot after
watering was collected and returned to the pots, Codling concluded that the
mineral level reduction most likely resulted from plant uptake, the article
desalination process shows promise for developing countries and fracking site
Optimization of a
humidification–dehumidification (HDH) system could provide a solution for both
desalination and operations treating water from natural gas wells.
Deep water that flows out along with
natural gas, called produced water, often contains more salt than oceanwater as
well as other minerals. But a process developed by a team of Massachusetts
Institute of Technology (MIT; Cambridge) researchers and collaborators at King
Fahd University of Petroleum and Minerals (Dhahran, Saudi Arabia) may offer a
less expensive and more efficient solution, according to an MIT news release.
The process is a variation on traditional distillation
where salt water is vaporized and condensed on a cold surface, separating salt
from water through evaporation. But the traditional process is energy-intensive
and costly because water must be heated to the boiling point while condensing
surfaces must be kept cold, the news release says.
For the new process, water that is well
below boiling point is vaporized through direct contact with a carrier gas and
bubbled through cooler water where purified vapor condenses, the news release
says. Because the temperature difference between the warm and cool water is
less than conventional dehumidifiers and the surface area provided by the
bubbles is greater than that of a flat condenser surface, the process requires
less energy and is more efficient.
MIT and King Fahd University began
collaborating in an effort to provide water to off-the-water-grid regions in
the developing world. They sought to create a process that increased energy and
thermal efficiency while reducing system size and cost, the news release says.
The optimal production capacity for this HDH system is about 1200 to 2400 L/d
of clean water, but its size can be increased by adding more modules, the news
The system is designed to desalinate water
in developing countries. But, because the system’s efficiency is unaffected by
the amount of salt in water, it also can produce clean water from hydraulic
fracturing produced water.
The team constructed a 4-m-tall
(12-ft-tall) test unit that ran continuously for weeks and produced almost 700
L/d of water that met drinking water standards, the news release says.
The team has filed to receive patents for
the system and created a company to commercialize it. The team plans to scale
up the system to about 2- to 3-times larger than the test unit. Prakash
Narayan, MIT researcher on the team, estimates that the first commercial plants
using this system could be operational within 2 years, the news release says.
March WER reveals optimal dissolved
oxygen for nitrification–denitrification
from the Harbin (China) Institute of Technology found the optimal dissolved
oxygen range for simultaneous nitrification–denitrification. In this process,
high dissolved oxygen concentrations can cause inferior nitrogen removal
because oxygen inhibits the denitrifying process, according to the research
The research, published in the March 2013 issue of Water
Environment Research (WER), determined that nitrate removal rates
gradually diminish as dissolved oxygen concentration increases to higher than 6
The researchers evaluated different effects of dissolved
oxygen on simultaneous nitrification–denitrification performance in
polyurethane foam contact oxidation reactors in a municipal wastewater
treatment process. The study found that nitrogen removal remained optimal
within the dissolved oxygen range of 0.5 to 1 mg/L, where removal efficiencies
were 85.1% for ammonium and 70.6% for total nitrogen.
researchers also performed denaturing gradient gel electrophoresis analysis to
record changes to the diversity of the microbial community as dissolved oxygen
values increase. The study found that the microbial nitrifiers in reactors were
Nitrosospira sp., Nitrosomonas sp., and Nitrospira sp.,
the report says.
The article, “Evaluating the Effect of Dissolved
Oxygen on Simultaneous Nitrification and Denitrification in Polyurethane Foam
Contact Oxidation Reactors,” is available as an open-access document and can be
downloaded free at http://goo.gl/77EGC.