Passive Aeration

Passive Aeration happens in non-reactor systems and includes: Triangular Windrow, Mat Windrow, Sole Aeration, Chimney Aeration, and Dome Aeration Technology (DAT) .
DAT is considered one of the cost efficient practical methods for aeration of compost winrows. Dome Aeration Technology is an open, non-reactor system where the degradation process takes place in a static (no turning) windrow. Continuous natural aeration is achieved by thermally driven advection, caused by temperature differences between the degrading material and the outside environment.


source:  Effective pine bark composting with the Dome Aeration Technology
Cristina Trois , Andreas Polster
Waste Management 27 (2007) 96–105

Biosolid

The Clean Water Act requires that communities treat their wastewater to return this resource safely to the environment. When wastewater is treated, the process produces a semisolid, nutrient-rich byproduct known as biosolids. When treated and processed properly, biosolids can be recycled and applied to crop land to improve soil quality and productivity because of the nutrients and organic matter that they contain. Historically called sewage sludge, biosolids is the term now used to emphasize the beneficial nature of this recyclable material. Biosolids often contain approximately 93 to 99 percent water, as well as solids and dissolved substances present in the wastewater or added during wastewater or biosolids treatment processes. The quantity of municipal biosolids produced annually in the United States has increased dramatically since 1972, from roughly 4.6 million dry tons in 1972 (Bastian, 1997) to 6.9 million dry tons in 1998. This is a 50 percent increase from 1972, when the Clean Water Act first imposed minimum treatment requirements for municipal wastewater, and is greater than the 29 percent increase in U.S. population from 1972 to 1998 (Council of Economic Advisors, 1999).
source:  EPA website - A report on Biosolids Generation, Use, and Disposal in The United States

Chimney effect

The natural phenomena of the density difference between a hot and cold air column that creates a natural flow through a chimney is called the Chimney effect.

The gas temperature inside the flue gas stack is around 140 ° C. The outside ambient air temperature is around say 30° C. Consider this as two air columns connected at the bottom. The high density and heavier cold air will be always pushing the low density and lighter hot gases up. This causes the natural flow of gases up the flue gas stack. This pressure difference that pushes the hot gas up the flue gas stack or the chimney is the 'chimney or stack effect'.

Depending on the height it can be gentle draught or heavy suction. This is the chimney or stack effect.

In numerical terms this can be represented as
Chimney effect = 353 x Chimney Height x [1/ Stack gas temperature – 1/ Ambient Temperature]
Where:
Chimney effect is in mm of water column.
Chimney height is in mteres.
Temperatures are in ° Kelvin.

Read more: http://www.brighthub.com/engineering/mechanical/articles/29769.aspx#ixzz1K5YHq9w4

Anaerobic Digestion

Anaerobic Digestion
Anaerobic digestion involves biologically stabilizing biosolids in a closed tank to
reduce the organic content, mass, odor (and the potential to generate odor),
and pathogen content of biosolids. In this process, microorganisms consume a
part of the organic portion of the biosolids. Anaerobic bacteria that thrive in the
oxygen-free environment convert organic solids to carbon dioxide, methane
(which can be recovered and used for energy), and ammonia. Anaerobic
digestion is one of the most widely used biosolids stabilization practices,
especially in larger treatment works, partly because of its methane recovery
potential. Anaerobic digestion is typically operated at about 35o C (95o F), but
also can be operated at higher temperatures (greater than 55o C [131o F]) to
further reduce solids and pathogen content of the stabilized biosolids.

source: EPA website

Stormwater Management

Stormwater runoff is excess water not absorbed by soil after heavy rains. It flows over surfaces such as roads, parking lots, building roofs, driveways, lawns, and gardens. On its journey to larger bodies of water (streams, lakes, and rivers), municipal and industrial stormwater can carry a wide range of potentially harmful environmental contaminants, such as metals, oil and grease, pesticides, and fertilizers. These types of contaminants pollute rural water, damage recreational and commercial fisheries, and degrade the beauty of affected waterways, among other things. Stormwater runoff must be treated before it is discharged into water to meet the U.S. Environmental Protection Agency’s National Pollutant Discharge Elimination System regulations. To comply, some municipalities and industries are turning to solutions that involve compost technology instead of more expensive traditional treatment methods, such as vegetated filter strips or grassy swales (phytoremediation) and holding ponds. These traditional methods require much larger tracts of land than methods utilizing compost and are limited in their removal of contaminants. In one industrial area,
for example, a traditional holding pond required 3.5 acres and cost $45,000, while a compost stormwater system, designed to handle the same amount of runoff, required only 0.5 acre, required less maintenance, and cost $17,300.
Source: EPA website