Lecture 14 Degradasi & Pengelolaan Tanah.pdf

Materi 14. Degradasi dan Dasar Pengelolaan Tanah

Degradasi Tanah• Proses global daerah tropika basah paling dominan

• Bentuk Utama Degradasi Tanah• Merosotnya kandungan unsur hara dan bahan organik

tanah

• Erosi

• Penyebab degradasi• Pengolahan & penggunaan tanah berlebihan tanpa

memperhatikan daya dukung lingkungan / tanah

• Budidaya tanaman tanpa kompensasi hara yang hilangkartena digunakan tanaman juga menyebabkandegradasi tanah

Tipe Degradasi Tanah• Erosi Tanah

– Erosi oleh air

– Erosi oleh angin

• Degradasi Sifat Kimia

– Hilangnya unsur hara atau bahan organik; salinisasi, pemasaman, polusi tanah, menurunnya kesuburan tanah

• Degradasi Sifat Fisik

– Pemadatan tanah, pengerasan tanah

Tindakan Konservasi Tanah• Berbagai tindakan konservasi tanah dapat mengurangi

erosi tanah

• Praktek pengelolaan tanah / lahan, seperti pengolahan tanah, sistem tanam mempengaruhi erosi dan solusinya

• Jika rotasi tanaman atau perubahan cara pengolahan tanah tidak cukup untuk mengendalikan erosi, maka kombinasi keduanya bisa dilakukan. Misalnya, contour plowing, strip cropping, atau terracing

Tipe tindakan konservasi• Agronomis

• seperti; tanaman penutup tanah, metode budidaya konservasi, penanaman pada kontour

• Vegetatif

• seperti, menanam tanaman pagar (jalur vegetasi), pagar tanaman hidup, dan tanaman pematah angin

• Struktural

• seperti, pembuatan teras, saluran, dan pagar pembatas

Strategi Pengelolaan Kesuburan Tanah

Pengelolaan Bahan Organik

Pengolahan Tanah

Pengelolaan Masukan Bahan Kimia

Pengelolaan Pemadatan Tanah

Pengelolaan Residu Tanaman

Pengelolaan Diversitas

Berbagai Tindakan Pengelolaan Kesuburan Tanah (umum di Indonesia)

Pembakaran

Pemulsaan

Pupuk hijau

Tumpang sari

Masa Bero hijau

Agroforestri

Bioremediation Bioremediation is the use of microorganisms to

destroy or immobilize waste materials

Microorganisms include:

Bacteria (aerobic and anaerobic)

Fungi

Actinomycetes (filamentous bacteria)

Bioremediation mechanism Microorganisms destroy organic contaminants in the

course of using the chemicals for their own growth and reproduction

Organic chemicals provide: carbon, source of cell building material

electrons, source of energy

Cells catalyze oxidation of organic chemicals (electron donors), causing transfer of electrons from organic chemicals to some electron acceptor

Electron acceptors Electron acceptors: In aerobic oxidation, acceptor is oxygen In anaerobic, acceptor is (with decreasing efficiency):

Nitrate manganese

iron

sulfate

Microorganisms also need essential nutrients such as nitrogen and phosphorus

Bacterial growth Typically very rapid if food (carbon source) is present:

population doubles every 45 minutes

Pristine soils contain 100 to 1000 aerobic bacteria per gram of soil

Increases to 105 within one week if carbon source is introduced

Limitations to biodegradation Adequate bacterial concentrations (although

populations generally increase if there is food present) Electron acceptors Nutrients (e.g., nitrogen and phosphorus) Non-toxic conditions (NAPL pools are likely to be toxic) Minimum carbon source (which may exceed regulatory limits

for toxic chemicals)

Note that rapid growth may be limited by diffusive or advective transport of any of the above

History of bioremediation 1972 - First commercial application: Sun Oil pipeline

spill in Ambler, Pennsylvania

1970s - Continuing bioremediation projects by Richard Raymond of Sun Oil

mid-1980s - emphasis on bioengineering organisms for bioremediation. This technology did not live up to its initial promise

1990s - emphasis switched to greater reliance on natural microorganisms and techniques to enhance their performance

Relative biodegradability Simple hydrocarbons and petroleum fuels

degradability decreases as molecular weight and degree of branching increase Aromatic hydrocarbons

one or two ring compounds degrade readily, higher molecular weight compounds less readily

Alcohols, esters Nitrobenzenes and ethers degrade slowly Chlorinated hydrocarbons

decreasing degradability within increasing chlorine substitution – highly chlorinated compounds like PCBs and chlorinated solvents do not appreciably degrade aerobically

Pesticides are not readily degraded

Bioremediation technologies for soil

Composting – addition of moisture and nutrients, regular mixing for aeration

Biopiles – ex-situ aeration of soil

Bioventing – in-situ aeration of soil

Land treatment – application of organic materials to natural soils followed by irrigation and tilling

Composting Composting is a process by which organic wastes are degraded by microorganisms, typically at elevated

temperatures. Typical compost temperatures are in the range of 55° to 65° Celsius. The increased temperatures result from heat produced by microorganisms during the degradation of the organic material in the waste. Windrow composting has been demonstrated using the following basic steps. First, contaminated soils are excavated and screened to remove large rocks and debris. The soil is transported to a composting pad with a temporary structure to provide containment and protection from weather extremes. Amendments (straw, alfalfa, manure, agricultural wastes and wood chips) are used for bulking agents and as a supplemental carbon source. Soil and amendments are layered into long piles, known as windrows. The windrow is thoroughly mixed by turning with a commercially available windrow turning machine. Moisture, pH, temperature, and explosives concentration are monitored. At the completion of the composting period the windrows would be disassembled and the compost is taken to the final disposal area.

PROCESS PERFORMANCE Windrow composting has been demonstrated as an effective technology for treatment of explosives-

contaminated soil. During a field demonstration conducted by USAEC at UMDA, TNT reductions were as high as 99.7% at 30% soil in 40 days of operation, with the majority of removal occurring in the first 20 days of operation. Maximum removal efficiencies for RDX and HMX were 99.8% and 96.8% respectively.

BIOPILE Biopile treatment is a full-scale technology in which excavated soils are mixed with

soil amendments, placed on a treatment area, and bioremediated using forced aeration. The contaminants are reduced to carbon dioxide and water.

Developed by the Naval Facilities Engineering Service Center, the basic biopile system includes a treatment bed, an aeration system, an irrigation/nutrient system and a leachate collection system.

Moisture, heat, nutrients, oxygen, and pH are controlled to enhance biodegradation. The irrigation/nutrient system is buried under the soil to pass air and nutrients either by vacuum or positive pressure. Soil piles can be up to 20 feet high and may be covered with plastic to control runoff, evaporation and volatilization, and to promote solar heating. If volatile organic compounds (VOCs) in the soil volatilize into the air stream, the air leaving the soil may be treated to remove or destroy the VOCs before they are discharged into the atmosphere. Treatment time is typically 3 to 6 months.

Requirements for soil bioremediation

Bioventing Developed by the Air Force Center for Environmental Excellence,

bioventing stimulates the in-situ biodegradation of POLs by providing oxygen to microorganisms in the soil. The system supplies oxygen by injecting air directly into the residual contamination (see below). In contrast to soil vapor vacuum extraction (SVE), bioventing uses low airflow rates to provide only enough oxygen to sustain microbial activity. Optimal flow rates maximize biodegradation as vapors move slowly through biologically active soil while minimizing volatilization of contaminants.

A basic bioventing system includes a well and a blower, which pumps air through the well and into the soil. Bioventing has been approved in 38 states and all 10 Environmental Protection Agency (EPA) regions.

Bioremediation technologyfor floating product

Bioslurping – two-phase vapor extraction that also encourages biodegradation

Bioremediation technologiesfor ground water

Bioremediation - addition of one or more of the following to stimulate bacterial growth:

Nutrients

Carbon source (dextrose, molasses)

Oxygen

Circulation

Amendment introduction methods

Injection wells

Infiltration

Passive introduction of chemicals

Amendment introduction via injection wells

Amendment introduction via passive introduction

Oxygen release compound (magnesium peroxide):

MgO2 + H2O → ½ O2 + Mg(OH)2

Amendments to createanaerobic conditions Carbon sources: Acetate

Propionate

Ethanol

Lactate

Molasses

Vegetable oil

Hydrogen Release Compound (Lactic acid)

Soil bioremediation Introduction

Bioremediation, when properly managed, is an environmentally sound and cost-effective method of treating soils containing organic chemicals. Bioremediation may then enable appropriate reuse of the treated soil and minimise disposal of waste soil to landfill, whilst providing for adequate protection of human health and the environment.

Soil bioremediation There are two types of bioremediation

ex situ (remove and treat),

in situ (treat in place)

can be performed on soil or underground water.

Suitability for bioremediation

Bioremediation is not a new concept and is being increasingly used as a relatively economical environmental remediation technology.

The ex situ bioremediation treatment of soil is generally undertaken in contained and managed biopiles or, subject to limitations, by landfarming.

Suitability for bioremediation

bioremediation is defined as an accelerated process using micro-organisms (indigenous or introduced) and other manipulations to degrade and detoxify organic substances to harmless compounds, such as carbon dioxide and water, in a confined and controlled environment.

Suitability for bioremediation

Bioremediation is suitable for the treatment of a variety of organic chemicals, including:

volatile organic compounds

benzene, toluene, ethyl benzene, xylene (BTEX) compounds

phenolic compounds

polycyclic aromatic hydrocarbons (PAHs) (particularly the simpler aromatic compounds)

petroleum hydrocarbons

nitroaromatic compounds

Bioremediation is generally not a suitable treatment option for soils containing:

metals

complex (high molecular weight) PAHs

chlorinated hydrocarbons.

There are generally three stages to a soil bioremediation project: a laboratory-based study to determine the biodegradability of

chemical substances and the ability of the indigenous or introduced micro-organisms to degrade them; generally performed off site

a pilot trial, either on site or in the laboratory or a combination of both, to provide further data necessary for the design of the full-scale treatment

full-scale bioremediation, conducted on site

Use of bioremediation1. on-site treatment of the chemical substances to

reduce risk to an acceptable level

2. off-site treatment of excavated soil to reduce risk to an acceptable level, after which the treated soil is returned to the site

3. containment of soil on site with a properly designed barrier

4. disposal of affected soil to an approved landfill.

Landfarming Landfarming is a form of bioremediation. It is an above-ground process that involves placing

affected soil on a prepared surface and aerating it by regular turning.

Soil amendments (for example, fertilisers) are sometimes added.

The movement of oxygen through the soil pile promotes aerobic degradation of organic chemicals.

Landfarming is a passive form of bioremediation and generally requires an extended timef

Biodegradation (Biooxidation)

The biochemical transformation of an organic chemical to another form as a result of highly complex chain of events interacted between the specific compound, microorganism, and the environmental conditions.

Operational Categories Primary biodegradation

Minimal amount of change

Ultimate biodegradation Conversion into CO , H O, CH , and inorganic

substances

Acceptable biodegradation

Change to a non-toxic compound

Bioengineered BacteriaAlteration of the DNA code of the

existing species or development of new bacteria through gene splicing techniques of molecular biology.

Persistent Compound A chemical that fails to undergo biodegradation

under a specific set of conditions. A chemical may be inherently biodegradable yet persist in the environment

Recalcitrant CompoundA chemical that has an inherent

resistance to any degree of

biodegradation. e.g., toxaphene, dieldrin, endrin

Biogenic Compounds Naturally occurring compounds that have been

present for millions of years. Thus, there are organisms somewhere in the biosphere that can initiate their biodegradation

Xenobiotic Compounds Compounds that are foreign to the biosphere,

having been present for only an instant on the evolutionary time scale. May or may not be biodegradable

Bioremediation/Biotreatment The manipulation of living systems to bring about

desired chemical and physical changes in a confined and regulated environment

Gratuitous Metabolism Reactions involving enzymes having high substrate

specificity with respect to catalytic function but low specificity with respect to substrate binding

Relationship between Enzyme Actionand Gratuitous metabolism +

Substrate

Enzyme:active site on surface

Enzyme-substrate complex

End products

Free enzyme

+

Substrate

Enzyme:active site on surface

Enzyme-substrate complex

End products

Free enzyme

Cometabolism/Cooxidation The transformation of a non-growth substrate in

the obligate presence of a growth substrate or another transform- able compound

Distinction between Surface andSubsurface Remediation

Surface treatment

Dominant electron acceptor is oxygen supplied directly from the atmosphere.

Subsurface treatment

Electron acceptor is supplied by perfusing the contaminated material with water or air.

Bioremediation Limiting Factors1. Distribution of the waste which may limit

microorganism access to the waste

2. Supply of nutrients required for metabolism

3. Toxicity of the waste due to concentration and/or type of constituents present

4. Formation and accumulation of toxic byproducts

Bioremediation Limiting Factors5. Inadequate population(s) of requisite

microorganisms

6. Non-competitiveness of non-survivability of inoculated cultures

7. Inadequate management of the system

Rate of Bioremediation If the supply of mineral nutrients is adequate, the rate

of bioremediation is the rate of supply of electron acceptor. As a result, the rate of remediation is directly proportional to the concentration of electronacceptor in the injected water and the flow velocity of water through the source area

Bioremediation

57

In Situ Bioremediation

Watertable

Infiltrationgallery

Control building

To carbonfilter

Contaminatedarea

Mineralnutrients

Nitratesolution

58

BIOREMEDIATION STRATEGIES

In situ bioremediation the most desirable options due to lower cost and less

disturbance since they provide the treatment in place avoiding excavation and transport of contaminants.

In situtreatment is limited by the depth of the soil that can be effectively treated. In many soils effective oxygen

diffusion for desirable rates of bioremediation extend to a range of only a few centimeters to about 30 cm into the soil, although depths of 60 cm and greater have been effectively treated in some cases.

The most important land treatments are:

Bioventing

In situ biodegradation

Biosparging

Bioaugmentation

Bioventing the most common in situ treatment and involves

supplying air and nutrients through wells to contaminated soil to stimulate the indigenous bacteria.

Bioventing employs low air flow rates and provides only the amount of oxygen necessary for the biodegradation while minimizing volatilization and release of contaminants to the atmosphere.

It works for simple hydrocarbons and can be used where the contamination is deep under the surface.

In situ biodegradation involves supplying oxygen and nutrients by circulating

aqueous solutions through contaminated soils to stimulate naturally occurring bacteria to degrade organic contaminants.

It can be used for soil and groundwater. Generally, this technique includes conditions such as the infiltration of water-containing nutrients and oxygen or other electron acceptors for groundwater treatment.

Biosparging involves the injection of air under pressure below the water

table to increase groundwater oxygen concentrations and enhance the rate of biological degradation of contaminants by naturally occurring bacteria.

Biosparging increases the mixing in the saturated zone and thereby increases the contact between soil and groundwater.

The ease and low cost of installing small-diameter air injection points allows considerable flexibility in the design and construction of the system.

Bioaugmentation Bioremediation frequently involves the addition of

microorganisms indigenous or exogenous to the contaminated sites.

Two factors limit the use of added microbial cultures in a land treatment unit: nonindigenous cultures rarely compete well enough with an

indigenous population to develop and sustain useful population levels

most soils with long-term exposure to biodegradable waste have indigenous microorganisms that are effective degrades if the land treatment unit is well managed.

Ex situ bioremediation These techniques involve the excavation or removal of

contaminated soil from ground.

Landfarming

Composting

Biopiles

Bioreactors

Landfarming is a simple technique in which contaminated soil is excavated and

spread over a prepared bed and periodically tilled until pollutants are degraded.

The goal is to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.

In general, the practice is limited to the treatment of superficial 10–35 cm of soil.

Since landfarming has the potential to reduce monitoring and maintenance costs, as well as clean-up liabilities, it has received much attention as a disposal alternative.

Composting is a technique that involves combining contaminated

soil with nonhazardous organic amendants such as manure or agricultural wastes.

The presence of these organic materials supports the development of a rich microbial population and elevated temperature characteristic of com

Biopiles are a hybrid of landfarming and composting. Essentially,

engineered cells are constructed as aerated composted piles.

Typically used for treatment of surface contamination with petroleum hydrocarbons they are a refined version of landfarming that tend to control physical losses of the contaminants by leaching and volatilization.

Biopiles provide a favorable environment for indigenous aerobic and anaerobic microorganisms.

Bioreactors Slurry reactors or aqueous reactors are used for ex situ treatment of

contaminated soil and water pumped up from a contaminated plume.

Bioremediation in reactors involves the processing of contaminated solid material (soil, sediment, sludge) or water through an engineered containment system

A slurry bioreactor may be defined as a containment vessel and apparatus used to create a three-phase (solid, liquid, and gas) mixing condition to increase the bioremediation rate of soilbound and water-soluble pollutants as a water slurry of the contaminated soil and biomass (usually indigenous microorganisms) capable of degrading target contaminants

Bioreactors In general, the rate and extentof biodegradation are greater

in a bioreactor system than in situ or in solid-phase systems because the contained environment is more manageable and hence more controllable and predictable.

Despite the advantages of reactor systems, there are some disadvantages.

The contaminated soil requires pre treatment (e.g., excavation) or alternatively the contaminant can be stripped from the soil via soil washing or physical extraction (e.g., vacuum extraction) before being placed in a biore

Summary of bioremediation strategies

Advantages of bioremediation Bioremediation is a natural process and is therefore perceived by the

public as an acceptable waste treatment process for contaminated material such as soil. Microbes able to degrade the contaminant increase in numbers when the contaminant is present; when the contaminant is degraded, the biodegradative population declines. The residues for the treatment are usually harmless products and include carbon dioxide, water, and cell biomass.

Theoretically, bioremediation is useful for the complete destruction of a wide variety of contaminants. Many compounds that are legally considered to be hazardous can be transformed to harmless products. This eliminates the chance of future liability associated with treatment and disposal of contaminated material.

Advantages of bioremediation Instead of transferring contaminants from one environmental medium

to another, for example, from land to water or air, the complete destruction of target pollutants is possible.

Bioremediation can often be carried out on site, often without causing a major disruption of normal activities. This also eliminates the need to transport quantities of waste off site and the potential threats to human health and the environment that can arise during transportation.

Bioremediation can prove less expensive than other technologies that are used for clean-up of hazardous waste.

Disadvantages of bioremediation Bioremediation is limited to those compounds that are

biodegradable. Not all compounds are susceptible to rapid and complete degradation.

There are some concerns that the products of biodegradation may be more persistent or toxic than the parent compound.

Biological processes are often highly specific. Important site factors required for success include the presence of metabolically capable microbial populations, suitable environmental growth conditions, and appropriate levels of nutrients and contaminants.

It is difficult to extrapolate from bench and pilot-scale studies to full-scale field operatio

Disadvantages of bioremediation Research is needed to develop and engineer bioremediation

technologies that are appropriate for sites with complex mixtures of contaminants that are not evenly dispersed in the environment. Contaminants may be present as solids, liquids, and gases.

Bioremediation often takes longer than other treatment options, such as excavation and removal of soil or incineration.

Regulatory uncertainty remains regarding acceptable performance criteria for bioremediation. There is no accepted definition of “clean”, evaluating performance of bioremediation is difficult, and there are no acceptable endpoints for bioremediation treatments.

PHYTOREMEDIATION

In natural ecosystems, plants act as filters and metabolize substances generated by nature. Phytoremediation is an emerging technology that uses plants to remove contaminants from soil and water.

The term “phytoremediation” is relatively new, coined in 1991. Its potential for encouraging the biodegradation of organic contaminants requires further research, although it may be a promising area for the future.

Introduction

classified based on the contaminant fate:

phytoextraction,

phytotransformation,

phytostabilization,

phytodegradation,

rhizofiltration,

even if a combination of these can be found in nature

types of phytoremediation techniques

is the process used by the plants to accumulate contaminants into the roots and aboveground shoots or leaves.

This technique saves tremendous remediation cost by accumulating low levels of contaminants from a widespread area.

Unlike the degradation mechanisms, this process produces a mass of plants and contaminants (usually metals) that can be transported for disposal or recycling.

Phytoextraction or phytoaccumulation

refers to the uptake of organic contaminants from soil, sediments, or water and, subsequently, their transformation to more stable, less toxic, or less mobile form.

Metal chromium can be reduced from hexavalent to trivalent chromium, which is a less mobile and noncarcinogenic form.

Phytotransformation

is a technique in which plants reduce the mobility and migration of contaminated soil.

Leachable constituents are adsorbed and bound into the plant structure so that they form a stable mass of plant from which the contaminants will not reenter the environment.

Phytostabilization

is the breakdown of contaminants through the activity existing in the rhizosphere.

This activity is due to the presence of proteins and enzymes produced by the plants or by soil organisms such as bacteria, yeast, and fungi.

Rhizodegradation is a symbiotic relationship that has evolved between plants and microbes.

Plants provide nutrients necessary for the microbes to thrive, while microbes provide a healthier soil environment.

Phytodegradation or rhizodegradation

is a water remediation technique that involves the uptake of contaminants by plant roots.

Rhizofiltration is used to reduce contamination in natural wetlands and estuary areas.

Rhizofiltration

Overview of phytoremediation applications

Phytoremediation is well suited for use at very large field sites where other methods of remediation are not cost effective or practicable; at sites with a low concentration of contaminants where only polish treatment is required over long periods of time; and in conjunction with other technologies where vegetation is used as a final cap and closure of the site.

There are some limitations to the technology that it is necessary to consider carefully before it is selected for site remediation: long duration of time for remediation, potential contamination of the vegetation and food chain, and difficulty establishing and maintaining vegetation at some sites with high toxic levels.

summary