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B. Organic Wastes Handling Effects

B. Organic Wastes Handling Effects

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14



G. S. TOOR ET AL.



The following sections describe the major treatment and storage practices

used today.

1.



Treatments



Organic waste treatments consist of physical and chemical to biological

processes, which are often needed to reduce the volumes of waste, destroy

pathogens, control odors, and improve palatability. These treatments

can also modify the physical, chemical, and biological characteristics of

wastes, resulting in heterogeneity in P speciation from one production site

to another. The following section summarizes the common treatments.

a. Physical Treatment Physical treatment of wastes involves solid–liquid separation by sedimentation or screening and is mostly used for dairy

and swine manures and biosolids. The separated solids can then be composted, reused as bedding, or feed, or pelletilized, or directly applied to soil

as an amendment. The liquids can be used to flush the animal house to

remove manure before using to supply plant nutrients. The major advantage

of this process is lower transport costs due to reduction in waste volume,

which can be of significant concern in large animal production facilities.

Other alternative methods of manure use, primarily for poultry litter and

biosolids, include drying, incineration, and pyrolysis. A detailed discussion

of physical treatment processes for wastes has been provided by Moore

(1993) and Day and Funk (1998).

b. Chemical Treatment Organic wastes can be treated with chemicals

to precipitate particulates and colloidal matter, to control pH and odor, and

to enhance biological treatment. The most commonly used coagulants in

wastewater are aluminum sulfate, ferric sulfate or chloride, and lime. Some

polyelectrolytes and polymers have also been used in biosolids and manures

(Dao and Daniel, 2002; Dao et al., 2001). In poultry houses, sodium bisulfite

is used for NH3 control, litter acidification, and for pathogen reduction

(Salmonella and Campylobacter) (Moore et al., 1996; Yang et al., 1998).

Another common chemical additive used today in poultry houses is aluminum sulfate (alum), which reduces soluble inorganic P concentrations and

NH3 emissions (Moore et al., 2000; Sims and Luka‐McCaVerty, 2002).

Usage of alum and aluminum chloride to reduce soluble inorganic P in

swine manure has also been documented (Smith et al., 2001).

c. Biological Treatment Biological treatment can significantly reduce

the solids content of waste by the action of biological organisms in the

presence (aerobic) or absence (anaerobic) of oxygen, thus changing the

physical and chemical properties of the waste. Wastes are composed of



CHARACTERIZATION OF P IN ORGANIC WASTES



15



liquid and solid phases; the solids can be volatile or nonvolatile. Most of the

solids (75–80%) in fresh waste are organic in nature, which contain both

biodegradable and nonbiodegradable components. Microorganisms act on

the biodegradable component and convert organic C, O, and H to CO2 and

H2O in aerobic treatment and to CH4 and CO2 in anaerobic treatment.

Composting is a form of biological decomposition of organic matter by

aerobic thermophilic organisms (bacteria, fungi) that produces a stable

humus‐like material (Miller, 1991), which may then be used as a potting

material and soil amendment. It is most suited for solid manures and can

considerably reduce weight, volume, and odor. Recently, dead animal composting has become a common method to dispose of animal carcasses

(Cabrera and Sims, 2000; Murphy, 1988). In this process, protein and

carbohydrates are metabolized to CO2, H2O, NH3, and microbial cells.

The primary goals of these treatment steps are to promote easy separation

of solids from liquids and to reduce waste volume while retaining all of the

important nutrients (N, P, K).



2.



Storage



Organic wastes can be stored for short‐ or long‐term periods depending

upon the facilities in a given farm or facility. While solid manures such as

dairy and poultry are relatively easy to handle and may be composted prior to

land application, liquid manures such as swine manure and dairy eZuent

require additional storage structures such as concrete tanks or pits. Alternative low cost storage can be accomplished by storing liquid wastes in earthen

ponds or lagoons. From these structures, liquid manure may be either directly

pumped or carried in tanks for land application. The length and type of

facility for storing the waste can have a profound influence on the forms of

P, yet this important area of P research remains relatively unexplored. Toor

et al. (2005a) found that inorganic P was increased by approximately 10% of

total P by storing dairy feces in slurry pits due to microbial decomposition of

organic forms of P such as phytic acid, DNA, and phospholipids. McGrath

(2004) evaluated the eVect of poultry litter moisture content during storage

and reported that organic P was degraded to inorganic P. This degradation

increased the concentration and percentage of WEP in litter, suggesting that

the length of storage can significantly transform P species in resulting manures. On the other hand, Baxter et al. (2003) studied the eVects of pig diets

formulated with low phytic acid corn and phytase on P concentrations in pig

slurry stored up to 150 days. They observed that the relative proportion of

dissolved inorganic P as percent of total P in slurry decreased with increase in

storage time from 0 to 150 days because of microbial assimilation of inorganic

P or formation of less soluble P compounds.



16



IV.



G. S. TOOR ET AL.



METHODS FOR CHARACTERIZING PHOSPHORUS

IN ORGANIC WASTES



Knowledge of the total amounts of P in organic wastes may help to

determine the amount of supplemental mineral P fertilizer that must be

added for optimum crop yields, and can aid in P mass balance calculations

for farms and watersheds. However, total P measurements provide no information about the nature of chemical forms of P present in wastes, which will

be essential to understand fate and mobility of waste applied P. To partition

total P into more specific chemical P forms in organic wastes, a number of

methods, ranging from wet chemical and biological to spectroscopic have

been employed and are discussed in the following sections.



A. TOTAL PHOSPHORUS

Total P analysis of organic wastes involves conversion of insoluble components into soluble forms by some form of digestion followed by P determination in the solution. Digestion methods for wastes are principally

adapted from plant digestion methods as wastes contain digested plant

and feed components. A number of oxidizing agents, such as H2SO4,

HNO3, or HClO4 and H2O2, can be used. Detailed descriptions of the

methods that involve the use of (i) HNO3 and HClO4, (ii) H2SO4 and

HNO3, and (iii) H2SO4 and (NH4)2S2O8 or K2S2O8 are given by APHA

(1989). Other workers have used the H2SO4–H2O2–HF digestion (Bowman,

1988), Na2CO3 fusion (Olsen and Sommers, 1982), NaOBr–NaOH oxidation (Dick and Tabatabai, 1977), and ignition (Saunders and Williams, 1955)

methods for determining total P in soils. All these methods give comparable

results but may require special equipment such as fume hoods for HClO4

digestion, expensive platinum crucibles for the Na2CO3 fusion method, and

HF resistant glass material for the H2SO4–H2O2–HF digestion method. The

US Environmental Protection Agency’s (1986) method uses HNO3 followed

by H2O2, commonly referred as EPA 3050 and EPA3051, and has been

the most widely used method for digestion of manures and biosolids to

determine total P in the United States.

After digestion of wastes, P in solution can be measured colorimetrically

by the acid molybdate (Murphy and Riley, 1962) or by the ICP‐OES

method. The acid molybdate method was originally developed by Osmond

(1887) but became more widely used following modification by Murphy and

Riley (1962). Both acid molybdate and ICP give similar results for total

P analysis. However, the main diYculty can arise during analysis of inorganic P with acid molybdate in undigested samples (extracted with water or



CHARACTERIZATION OF P IN ORGANIC WASTES



17



Table VI

EVect of Method of Determination on Water Extractable Phosphorus in Poultry Littera

Water soluble P



Manure from diet

Normal corn (NORC)

High available P corn (HAP)

NORC‐0.1% NPP ỵ phytased

HAPC0.1% NPP ỵ phytasee

NORC0.2% NPP ỵ phytasef

HAPC0.2% NPP þ phytaseg

LSD0.05



Colorimetryb

(mg kgÀ1)



ICP‐OESc

(mg kgÀ1)



Overestimation

with ICP‐OES (%)



2394

2349

2157

1235

937

418

351



2486

2525

2395

1414

1305

541

235



4

7

10

13

28

23



a



Adapted from Sims et al. (2000).

Extraction of ‘‘as‐is’’ sample at 1:10 ratio (for 1 h), filtration through Whatman #4 and 0.45 mm

filters, P measured colorimetrically.

c

Extraction of ‘‘as‐is’’ sample at 1:10 ratio (for 1 h), filtration through Whatman #4 and 0.45 mm

filters, P measured by ICP‐OES.

d

Normal corn with 0.1% less nonphytate P (NPP) and phytase.

e

High available P corn with 0.1% less NPP and phytase.

f

Normal corn with 0.2% less NPP and phytase.

g

High available P corn with 0.2% less NPP and phytase.

Phytase was added at 650 U kgÀ1.

b



dilute acids) as sample acidification can result in hydrolysis of acid labile

organic compounds, such as sugar phosphates and monophosphate esters

(McKelvie et al., 1995), and cause inflated inorganic P values. On the other

hand, ICP measures both inorganic and all organic P. For example, in poultry

litter generated from modified diets, Sims et al. (2000) observed 4–28% higher

WEP measured by the ICP than the molybdate method (Table VI).

Another approach to rapidly analyze total P in manures is near‐infrared

reflectance spectroscopy (NIRS). The principle behind NIRS and information on its application in agricultural and food products can be found in

Burns and Cziurczak (1992) and Williams and Norris (2001). Although total

C and N concentrations have been successfully analyzed in manures by

NIRS, there have been mixed results when quantifying the total P content

in manures with NIRS: some workers obtained good correlation between the

total P measured with NIRS and total chemical analyses (Malley et al., 2002)

while others did not (Reeves, 2001; Reeves and Van Kessel, 2000). If this

method can be standardized to determine total P in wastes, it has the

potential to become a robust, cost‐eVective means for use in routine analyses

by manure testing laboratories and in situ field monitoring.



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