Reduce, reuse, recycle... with a profit
A new approach to wastewater treatment may be key in efforts to reduce, reuse, and recycle. Moreover, it can be profitable.
Phosphorus is an essential element for human nutrition. It plays multiple roles in the human body, including the development of bones and teeth. Fertilizer with phosphorus, applied to crops or lawns, enables healthy growth. Without it, the basic cells of plants and animals, and life itself, would not exist.
Typically, phosphorus is found in phosphate-containing minerals that are mined--a limited and non-renewable resource. The annual demand is rising quickly. However, once used, phosphorus is difficult to reclaim.
Where does the phosphorus go? In animals (including humans), urine contains phosphorus. Surface water carry large amounts of phosphorus from fields and lawns downstream. The result is phosphorus in water discharged by wastewater treatment plants (WWTPs).
"Whatever phosphorus we use and discharge into rivers and oceans is lost to the environment," says Rolf Halden, professor at the School of Sustainable Engineering and the Built Environment, and director of the Center for Environmental Security, Arizona State University.
Additionally, accumulation of phosphorus can result in problems like algae blooms in lakes and other surface water bodies. In turn, algae blooms deplete oxygen from the water, affecting the delicate balance of aquatic life. "This problem is observed in the seasonally recurring 'dead zone' of the Gulf of Mexico," says Halden.
Halden's group recently published a study in the Journal of Environmental Quality that examined methods for recovering phosphorus from wastewater using mathematical modeling. "WWTPs represent ground zero for addressing the problem of global phosphorus depletion," Halden says.
WWTPs in many cities are currently implementing methods to extract phosphorus before discharging wastewater into the environment. There are two main types of phosphorus recovery methods: chemical and biological.
In the chemical method, WWTP treat phosphorus dissolved in wastewater. The phosphorus then falls out of solution for easier removal. In the biological method, bacteria introduced into the water collect the phosphorus into removable sludge. A variation includes enhanced biological phosphorus removal (EBPR). This method selectively encourages bacteria that can accumulate phosphorus.
Choosing a method is complicated. "The region's water quality, size of the treatment plant, and economic considerations play a role in the selection," explains the study's lead author, Arjun Venkatesan.
Halden and Venkatesan's study focused on a combination approach. First, EBPR concentrated phosphorus in sludge. Next, chemical treatment helped phosphorus fall out to form struvite, a usable phosphate mineral. The study showed that a typical WWTP could reclaim approximately 490 tons of phosphorus in the form of struvite each year.
Conventional methods remove only 40%-50% of P, according to Venkatesan. The secondary treatment of sludge employed by EBPR "achieves an additional 35% mass reduction, for a total of about 90% removal," he says. EBPR helpfully avoids additional chemicals and reduces sludge production. Both these factors lower the cost of operation--a key consideration for WWTPs with limited budgets.
Reclaimed phosphorus pays off for the environment with less mining for phosphorus and improved surface water health. phosphorus recovered as struvite can also generate income. The team estimates that the WWTP used in their case study could generate $150,000 in annual revenue from this two-pronged approach. A plant with existing EBFR facilities can recoup the initial expenses in as little as 3 years.
"Nearly 367,500 tons per year of phosphorus could be generated with combined EBPR and struvite production," says Halden, in plants with treatment capacity similar to the one used in the case study.
Such a payload can be a welcomed payoff for conscientious communities.
Susan Fisk | EurekAlert!
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Power and Electrical Engineering
25.09.2017 | Health and Medicine
25.09.2017 | Physics and Astronomy