Composting - DOC

Document Sample
Composting - DOC Powered By Docstoc
					Industrial Composting Plant

          1 Introduction

     2. The Composting Process

            3. BioFilter

      4. Future Development’s

           5. Conclusion

           6. Appendix

The composting process is currently viewed primarily as a waste management method to
stabilize organic waste, such as manure, yard trimmings, municipal biosolids, and organic
urban wastes. The stabilized end-product (compost) is widely used as a soil amendment
to improve soil structure, provide plant nutrients, and facilitate the revegetation of
disturbed or eroded soil (Cole, 1994; Cole, 1995; Harmsen, 1994; McNabb, 1994).

  the composting process and the use of mature compost also provide an inexpensive and
technologically straightforward solution for managing hazardous industrial waste streams
(solid, air, or liquid) and for remediating soil contaminated with toxic organic compounds
(such as solvents and pesticides) and inorganic compounds (such as toxic metals). For
example, a large number of hydrocarbons, which are common industrial contaminants
found in soil and exhaust gas, degrade rapidly during the composting process or in other
compost-based processes.
Furthermore, the addition of mature compost to contaminated soil accelerates plant and
microbial degradation of organic contaminants and improves plant growth and
establishment in toxic soils. When mature compost is added to contaminated soils,
remediation costs are quite modest in comparison to conventionally used methods.
Mature compost also controls several plant diseases without the use of synthetic
fungicides or fumigants.

2. The Composting Process

The facility is designed having high bounded side’s and concrete Reception area, where
tipping, mixing and Aeration Hall filling and empting can occur with minimum sound
and visual impact

The Composting process is one of integrated recycling and composting. It is
differentiated by producing high quality compost suitable for unrestricted use.
The compost is made up from sludges that have been made by dewatering process’s,
which creates a biosolids ‘cake’ typically ranging from a solids content of 15% -35%, the
biosolids are blended with a bulking agent and carbon source. Wood chips, and other
various types of recycled wood materials, are typically used to meet both the bulking
agent and carbon requirements of the process.

the initial compost mix (recipe) possess the following characteristics: Since biosolids are
not generally in a form that allows for the free movement of air (oxygen), creating a
porous mass through the use of proper bulking agents is important.
The process consists of a rapid in-vessel composting phase, lasting 21 days, followed by
a slower maturation phase

The process utilizes temperature and humidity controlled Aeration Halls. Once mature,
the compost is finally screened to remove any glass and other fine physical contaminants.
The majority of the compost produced on this site is sent to agricultural uses.

The whole composting process is utilizes a vacuum system i.e maintained under negative
air pressure. All process air is extracted from the Aeration Hall and processed through an
enclosed biofilter, where the volatile compounds are converted to water and carbon
dioxide. After passing through the biofilters the cleaned process air is vented to

All composting methods share similar characteristic features and processes. Initially high
microbial activity and heat production cause temperatures within the compostable
material to rise rapidly into the thermophilic range (50 oC and higher). This temperature
range is maintained by periodic turning or the use of controlled air flow (Viel, 1987).
After the rapidly degradable components are consumed, temperatures gradually fall
during the "curing" stage

At the end of this stage, the material is no longer self-heating, and the finished Compost
is ready for use. Substantial changes occur in microbial populations and species
abundance during the various temperature stages (Gupta, 1987). Mesophilic bacteria and
fungi are dominant in the initial warming period, thermophilic bacteria (especially
actinomycetes) during the high temperature phase, and mesophilic bacteria and fungi
during the curing phase

3. Biofilter

The biofilter is simply a bed of organic material (medium), typically a mixture of
compost and wood chips or shreds, about 10 to 18 inches deep. As air passes through the
biofilter the microbes on the organic material convert odorous gases to carbon dioxide
and water. The effectiveness of the biofilter is primarily a function of the amount of time
the odorous air spends in the biofilter (contact time) and the moisture content of the filter
material. Contact time is part of the biofilter design while moisture content is a function
of good management. The size (footprint) of the biofilter depends primarily on the
amount of air needing treatment. A typical biofilter will require 50 to 85 square feet per
1000 cubic feet per minute (cfm) of airflow.

Biofilters effectively remove odors from any mechanically ventilated facility. each
exhaust from the fan’s in the Ariation halls are duct to bring the air into a plenum under
the biofilter material. The air is treated as it is forced through the biofilter.
the existing exhaust fans. Typical exhaust fans do not have enough
To prevent media dry-out and subsequent biofilter failure, water needs to be added to the
media on a regular basis. A dry media would make the odor-removal performance of the
Biofilter decrease due to the reduced viability of the microbial population. Two means of
water addition were chosen for the design: sprinklers for surface irrigation to prevent
surface dry-out, and an in-line spray humidification system within the air duct to prevent
internal dry-out. The sprinkler system was designed for a uniform water distribution on
the biofilter surface with automatic operation. In-line spray humidification was used to
saturate the foul air within the air conveyance manifold shortly before the air enters the
biofilter. The in-line humidification system was installed immediately downstream of the
blower (see Figure 1). Although the biofilter media must remain moist, it should not
become saturated. Saturation creates malodorous anaerobic zones and increases blower
back pressure. If too much moisture is applied to the biofilter, nutrient wash-out may also
occur. The biofilter media is most stable when a net excess of water is applied; therefore,
drainage water is likely to be generated. Collection of drainage was included in the
design. The biofilter drainage water is collected in a 6-inch diameter corrugated
perforated HDPE pipe and routed to the activated sludge plant. Both the water used for
irrigation and the water used for in-line humidification are tertiary filtered effluent. Being
treated effluent, the water contains nutrients (nitrates, ammonia, and phosphates)
necessary for biological growth in the biofilter media.
ADAS (2001) Guidelines for the Application of
Sewage Sludge to Agricultural Land . 3rd Edition.
Edwards, M. A (1998) A Guide to In-Vessel Composting;
a directory of systems . The Composting
Association. Coventry.
NRAES (1992) On-Farm Composting Handbook.
Northeast Regional Agricultural Extension Service.
New York.
Scottish Executive (1997) Prevention of Environmental
Pollution from Agricultural Activity: A
Code of Good Practice. Scottish Executive. Edinburgh.

Shared By: