dec. - wur
TRANSCRIPT
)TA 1394 December 1982
IMINJ1D43 > 1 J o 4 I n s t i t u t e for Land and Water Management Research Wageningen
BIBLIOTHEEK STATSiMQQEBOUVr — _J
RESEARCH ON SOLID WASTE AND GROUNDWATER QUALITY IN THE U.S.A.
dr. J. Hoeks
Report on a tour through the U.S.A.
(May 9 through June 12, 1982)
Nota's van het Instituut zijn in principe interne communicatiemiddelen, dus geen officiële publikaties. Hun inhoud varieert sterk en kan zowel betrekking hebben op een eenvoudige weergave van cijferreeksen, als op een concluderende discussie van onderzoeksresultaten. In de meeste gevallen zullen de conclusies echter van voorlopige aard zijn omdat het onderzoek nog niet is afgesloten. Bepaalde nota's komen niet voor verspreiding buiten het Instituut in aanmerking
CENTRALE LANDBOUWCATALOGUS
2 9 DEC. 1982
0000 0460 9083
C O N T E N T S
page
1. INTRODUCTION 1
2. CONFERENCE ON RESOURCE RECOVERY FROM MUNICIPAL,
HAZARDOUS AND COAL SOLID WASTES (Miami Beach, Fl) 2
2.1. General 2
2.2. Energy recovery from municipal solid waste 2
2.3. Energy recovery from hazardous waste 3
2.4. Reuse and metal recovery 4
2.5. Recovery of landfill gas 5
2.6. Resource Recovery Plant near Miami 6
2.7. Literature 7
3. COURSE ON GROUNDWATER MODELING (Holcomb Institute,
Butler University, Indianapolis, IND.) 8
3.1. International Ground Water Modeling Centre (IGWMC) 8
3.2. The Prickett-Lonquist Models PLASM and TRANS 9
3.3. Literature 15
4. SOLID AND HAZARDOUS WASTE RESEARCH DIVISION, EPA
(Cincinnatti, OH) 15
4.1. General 15
4.2. Groundwater pollution near landfills 16
4.3. Lining and capping of landfills 17
4.4. Production and recovery of landfill gas 18
4.5. The CECOS landfill for disposal of hazardous
waste 18
4.6. Literature 19
page
5. SYMPOSIUM ON AQUIFER RESTORATION AND GROUNDWATER
MONITORING (Columbus, OH) 22
5.1. General 22
5.2. Withdrawal and interceptor wells 22
5.3. Surface capping 23
5.4. Impermeable vertical walls and immobilization
of contaminants 23
5.5. The use of computer models 24
5.6. Sampling of groundwater 25
5.7. Literature 26
6. GEORGIA INSTITUTE OF TECHNOLOGY (Atlanta, GA) 27
6.1. General 27
6.2. Stabilization processes in a landfill 27
6.3. Codisposal of low-level radioactive waste
and municipal refuse 28
6.4. Identification and chelating effect of organic
pollutants 29
6.5. Literature 29
7. DEPARTMENT OF SOIL AND CROP SCIENCES (A & M
University, College Station, TX) 32
7.1. General 32
7.2. Effect of liquid waste on clay liners 32
7.3. Modeling of groundwater pollution 33
7.4. Literature 34
8. U.S. WATER CONSERVATION LABORATORY (Phoenix, AR) 35
8.1. General 35
8.2. Reuse of sewage water 35
8.3. Water harvesting and irrigation 36
8.4. Crop production 37
8.5. Literature 38
page
9. MATRECON, Inc. (Oakland, CA) 40
9.1. General 40
9.2. Tests on lining materials for landfills 40
9.3. Selection of lining materials 41
9.4. Literature 41
10. PACIFIC GAS AND ELECTRIC COMPANY (San Francisco, CA) 43
10.1. General 43
10.2. Recovery of biogas at the Mountain View Landfill 43
10.3. Literature 45
APPENDIX: Itinerary 48
1. INTRODUCTION
The Institute for Land and Water Management Research (ICW) is
performing research on land and water management of the rural area.
Originally the research was entirely related to agriculture, but
gradually it became clear that it was no longer possible to examine
problems related to agriculture in an isolated way. Many other
interests compete for water, space and facilities in the rural area.
Therefore research on environmental aspects of both agricultural
and non-agricultural land use with special emphasis on soil and
(ground)water quality is now an important part of the research in the
Institute.
For the research on soil and groundwater pollution, as it
is going on in the Netherlands and especially within the Institute,
it was considered as highly important to become acquainted with the
latest developments in the U.S.A.
Considering research projects going on in the Institute an
itinerary was composed with help of the Solid and Hazardous Waste
Research Division, U.S. Environmental Protection Agency in
Cincinnatti (Ohio), comprising the following subjects of interest:
- groundwater quality modelling;
- transport and accumulation of contaminants in soil and groundwater;
- techniques for prediction of effects with regard to Environmental
Impact Assesment (EIA);
- methods of disposal/reuse of municipal and hazardous waste and
sewage water;
- leaching of contaminants from sanitary landfills;
- construction of liners to prevent groundwater pollution from
landfills;
- production and recovery of landfill gas.
The complete itinerary with names of institutes and persons
visited is given in Appendix 1.
2. CONFERENCE ON RESOURCE RECOVERY FROM MUNICIPAL, HAZARDOUS AND
COAL SOLID WASTES (Miami Beach, FL)
2.1. G e n e r a l
The conference was meant to give a state-of-the-art of the
techniques used for resource recovery from municipal, hazardous
and coal solid wastes, and to provide a forum of interdisciplinary
exchange between investigators from different backgrounds with
experience in different kinds of waste.
The attention for resource recovery from municipal solid waste
is strongly increasing in the USA, because of environmental problems
caused by other methods of waste disposal (air pollution, soil
pollution).
2.2. E n e r g y r e c o v e r y f r o m m u n i c i p a l
s o l i d w a s t e
Municipal solid waste (MSW) is considered as a potentially
attractive source of energy for replacement of gas, oil or coal
in steam and electricity generation. The energy may be recovered
by mass burning of the MSW or by burning refuse derived fuel (RDF)
in 'dedicated' boilers (waterwall incinerators designed specifically
for burning RDF). RDF is the combustible fraction of the MSW,
which is left after separating it from non-combustible fractions like
iron, non-ferrous metals and glass.
Compared with mass burning of MSW the ash content of RDF is
lower and the heat content is higher. Depending on the preparation
method the ash content of RDF may reduce to 7% (MSW: 25%) and the
heat content may increase to 7500 BTU/lb (MSW: 4500 BTU/lb).
The energy from MSW is recovered for 40% by mass incineration,
for 6% by modular combustion and for 52% by burning RDF. The RDF
may also be burnt as a supplemental fuel with coal or oil.
Several papers discussed the environmental consequences arising
from the combustion of MSW or RDF, like emissions into the atmosphere
(hydrogen chloride, NO , SO , particulates), the composition of
residues and the risk of corrosion of boilers.
Compared with fossil fuels the emission of hydrogen chloride
is considerably higher for RDF or RDF/coal mixtures. This aspect
deserves special attention because of corrosive action. However,
other papers reported no corrosion of boilers when coal and RDF
were cofired. Another problem may be the emission of dioxins,
particularly the highly toxic TCDD (2,3,7,8-tetra chlorodibenzo-
-p-dioxin).
The emissions of sulphur and nitrogen are lower for RDF, because
the contents of RDF are low compared with coal. When cofiring RDF
and coal the emission of SO reduces also because the sulphur (from
coal) reacts with calcium and iron (from RDF), forming CaSO, and
Fe-sulphates.
Because most metals are present in high concentrations in
solid waste, emission of heavy metals may be a problem. This is
especially true for Pb and Zn. The emissions vary with the technique
of separating RDF from MSW and with the burning temperature.
Problems like excessive slagging, abrasion of mechanical parts
and reduced energy content are highly related with the efficiency
of separating the non-combustible portion and removing inert fines
and glass from the RDF.
2.3. E n e r g y r e c o v e r y f r o m h a z a r d o u s
w a s t e
Hazardous waste may be a resource for recovery of energy and
valuable metals. Incineration leads to detoxification and volume
reduction and especially in case of wastes with a high heat content
the energy may be recovered.
Thermal destruction is appropiate for 70% of the listed wastes
in the USA. There are several types of incinerators, nearly 90%
of them have included energy recovery. The furnish temperature may
vary from 300 to 3500 °F. The Environmental Protection Agency (EPA)
has published a handbook on 'Hazardous Waste Incineration'.
An example is the use of liquid organic wastes as a fuel for
cement kilns. The advantage is that the cement making process involves
extremely high temperatures (2000 - 2600 °F) and long burning
temperatures (15 minutes), which insures that all waste is destroyed.
Moreover the capacity of a cement kiln to dispose of waste is quite
large. Suitable wastes are: spent solvents, industrial oils, greases
and paint residues, and residues from solvent reclamation operations.
2.4. R e u s e a n d m e t a l r e c o v e r y
Inorganic wastes, especially sludges from galvanic industries,
containing heavy metal hydroxides, may be used in brick production.
The clay blending process is especially valid to leave a number of
sludges innocuous because of the long burning times. Emissions of
fluorine, chlorine, sulphates and dust particles were not significantly
higher when sludges were mixed with clay. In some cases there was a
slight increase of heavy metal content in the dust particles. Sludge
addition did not cause remarkable variations in mechanical characteristics
of the product.
Fly ash may be used as a cementitious additive in concretes and
grouts together with Portland cement. The pozzolanic reactivity of
fly ash is largely a consequence of the presence of glassy material
(silicate particles). At this moment about 50% of the fly ash produced
is utilized, the other 50% has to be disposed of. The amount of fly ash
is expected to increase strongly in the near future because of the
increasing use of coal as a fuel for electric power generation.
At this moment about 600 x 10 tons of coal are consumed leaving
75 x 10 tons of fly ash. This amount is expected to be doubled in
1990.
Especially the aluminum in fly ash (about 20% A1„0~) is an
interesting resource for recovery because there are no natural
aluminum resources within the USA. Other interesting chemicals,
which may be recovered from fly ash are titanium oxide and many
trace metals (Mn, Co, Ni, Zn, Cd, Fe).
Research is going on now on different types of recovery processes,
like leaching of metals with acids, sintering, carbon chlorination
(i.e. extraction as volatile aluminum chloride), and bacterial
extraction. When all fly ash produced would be used for aluminum
recovery about 10 x 10 tons of aluminum metal could be produced
in 1990, which exceeds the annual US-demand for primary aluminum.
Because of the importance of aluminum even the feasibility of
aluminum recovery from clay soils rich in aluminum is investigated.
Other possibilities for recovery and reuse of valuable parts
from solid waste are:
- production of a feed for animals, e.g. from food wastes. One of
the major concerns is the spread of diseases. Therefore the waste
has to be treated. Thus the effect of temperature and exposure
time was studied, indicating that most bacteria were killed at
rather low temperatures (up to 30°C) within 72 hours;
- production of biogas from MSW, RDF and/or sludge, under controlled
conditions, by pyrolysis, hydrogénation or anaerobic digestion;
- use of sludge as a soil amendment in forests (forest products are
not consumed and thus are less likely to pose a health hazard).
Research indicated an increase in tree growth and an increase in
waterholding capacity and available nutrient status of the soil.
2.5. R e c o v e r y o f l a n d f i l l g a s
A few papers (two from Germany, one from Italy) discussed
research on recovery of landfill gas. In the German contributions
research on laboratory scale and field scale was discussed. One of
the conclusions was, that under optimum conditions in the laboratory
the main gas production phase in shredded refuse was terminated
after a period of 4 to 6 months.
In highly compacted refuse it took more time to reach the
methane fermentation stage than in less compacted refuse. In practice
methane fermentation will start within one year, when the refuse
is only moderately compacted and especially when leachate is
recirculated.
The quality of the leachate in a landfill depends on the stage
of fermentation. To minimize the chemical load of the leachate one
should try to reach the methane production phase in a landfill as
soon as possible. An effective degradation of fatty acids by methane
fermentation may be realized in a 'two-reactor' system, i.e. the
lower 2 meter of refuse is treated in such a way that methane
fermentation starts rather soon. In this case the fatty acids
produced in upper refuse layers will be converted to methane during
percolation through the lower layer. This new concept of sanitary
landfilling is now tested at the landfill of Lingen (W-Germany).
The gas produced in a landfill can be extracted and utilized
in gas engines producing electricity. At the landfill 'Am Lemberg'
(W-Germany) the landfill gas is burnt in boilers for heating of a
nearby greenhouse complex. Extraction from a horizontal withdrawal
system under natural pressure inside the landfill has given quite
good results with high methane contents in the gas (55-60%).
In Italy also research is going on about the feasibility
of landfill gas recovery. The alternatives studied are:
- distribution of landfill gas to nearby factories;
- transport to the nearest gas distribution network;
- installation of an electric power generator on the site.
The feasibility study indicated that generation of electricity
was the most attractive alternative.
In the USA several gas recovery projects are under operation
for several years (see Chapter 10). These experiences, however,
were not presented at the Conference.
2.6. R e s o u r c e R e c o v e r y P l a n t n e a r M i a m i
An excursion was made to Resources Recovery (Dade County), Inc.
near Miami.
In a resource recovery plant first of all the MSW is separated
into fractions by shredding (in hammermills), followed by magnetic
separation of ferrous material. Next the light combustible fraction
is separated from the heavier noncombustibles and further processed
to yield RDF. Aluminum and glass are recovered from the heavy fraction.
In this resource recovery plant 3,000 tons/day of MSW (domestic
garbage and trash) are processed to recover yearly:
- 62,000 tons of ferrous material;
- 3,000 tons of aluminum;
- 10,000 tons of non-ferrous material;
- 20 to 85,000 tons of glass, depending on quality desired;
- 400 to 500,000 Megawatt Hours as net output electricity generation.
The materials in the MSW are seperated by sieving and differences
in specific weight in a slurry according to the Black Clawson
principle. The combustible fraction (paper, organic garbage, plastic)
is processed to yield RDF. Next the RDF is fired in boilers to
produce steam for electricity generation. Per ton of RDF (i.e. about
70% of the MSW) about 120 kWh is produced. Ash and glass are used
as granulates in road construction. The total investment in the
plant amounted to $ 120 x 10 (1979).
The financial output of the recovery process was very good,
particularly thanks to the generation of electricity. The yearly
revenue of this plant is about $ 20 x 10 from the sale of electricity
and recycable materials.
2 . 7 . L i t e r a t u r e
ABSTRACTS OF THE PAPERS PRESENTED AT THE CONFERENCE ON RESOURCE
RECOVERY FROM MUNICIPAL, HAZARDOUS AND COAL SOLID WASTES
in Miami Beach, Florida (May, 10-12, 1982)
BROCHURE ON THE RESOURCE RECOVERY PLANT NEAR MIAMI (Address:
Resources Recovery (Dade County), Inc., P.O.Box 524056,
Miami, Florida 33152
3. COURSE ON GROUNDWATER MODELING (Holcomb Institute, Butler University,
Indianapolis, IND.)
3.1. I n t e r n a t i o n a l G r o u n d W a t e r M o d e l i n g
C e n t r e (IGWMC)
In 1978 the Holcomb Research Institute established the International
Ground Water Modeling Centre (IGWMC) whose principal objective is to
provide information on groundwater modeling. To this purpose, IGWMC
operates a clearinghouse for groundwater models, organizes and
conducts workshops, seminars and short-courses on groundwater modeling
and carries out a services-oriented research program.
The clearinghouse function is performed by collecting information
on groundwater models, both from the USA and abroad. After screening
and testing this information is stored on a computerised data base
now containing up to date information on hundreds of groundwater models.
First priority is given to making existing models more accessible
to potential users. Apart from an adequate documentation this also
includes training of the model users.
To facilitate the different activities the Center opted for a
four-department structure: Clearinghouse, Training and Education,
Research and Communication (see fig. 1).
The need for communication with different groups within the
groundwater community was met by developing an extensive publication
program including brochures, newsletters and reports. Especially
the Groundwater Modeling Newsletter covers all aspects of ground
water modeling. Furthermore complete lists are available on
documented groundwater models, mass transport models and programs
for hand-held calculators.
International Ground Water Modeling Center
Clearinqhouse
-storing & updating model information
-model information searches
-screening testing & selecting models
-computer programs & program documentation
I G W H C
Training & Education
-short courses
-seminars
-workshops
-individual assistance
Research
-model needs
-model use
-model development
Commun cations
-newsletter
-reports
-papers
-handling information requests
-general mailing
-documentation center
Fig. 1. Organization of IGWMC
3 . 2 . T h e P r i c k e t t - L o n n q u i s t M o d e l s P L A S M
a n d T R A N S
This course in May, 1982 was organized to instruct users about
the Prickett-Lonnquist Aquifer Simulation Model (PLASM) and the
expanded version of this model, which simulates the transport of
solutes in groundwater systems (TRANS).
The PLASM model has been widely used to study groundwater flow
problems and has been proven by numerous field applications to
solving complex problems in water supply, mining and reclamation
projects including stream-aquifer systems.
The mass transport model, i.e. the expanded version of PLASM,
incorporates processes like dispersion and diffusion,
retardation due to linear adsorption and first-order decay. The main
advantages of this model are its simplicity and ease of application
to groundwater flow processes pertinent to contamination and other
water quality problems. Dispersion is treated as a random process
and it is described by a statistical method. The model is therefore
called the 'Random-Walk' Solute Transport Model, shortly indicated
as model TRANS.
PLASM is a 2-Dimensional model and so is the mass transport model
TRANS. There is a 3-D version of PLASM but only for the waterflow,
not for transport of solutes.
The differential equation of continuity for the transport of
solutes in soil may be numerically solved in three ways:
- normal finite difference approximation (FD) this method is very
tricky and sensitive and may lead to instability problems;
- Method of Characteristics (MOC): two grid systems are needed, one
for calculation of flow velocities and another one for the
displacement of particles and calculation of new concentrations.
Particles must be present in all elements of the grid system.
This method is therefore time consuming.
- Random-Walk Model: needs only one grid system, because the
particles are running in a continuous space. Particles are
present only at the places of interest. This means that elements
can be empty. Disadvantages may be that, because the results have
a lumpy character, lots of particles are needed to get a more
'smooth' result. On the other hand the advantage is that solutions
are additive, i.e. when a first run is done with a number of
particles too low, a new run can be done and the two solutions can
be added.
The Random-Walk Model is in first instance meant for the horizontal
plane. Nevertheless it can be used for the vertical plane, but in
that case one should remember the features for the plane, e.g.
recharge in the horizontal plane is coming from above, so in the
vertical plane it is coming from aside.
The model is not appropiate for unsaturated conditions and does
not account for density flow.
The model includes retardation due to linear adsorption. The
retardation of a concentration front in groundwater relative to the
bulk mass of water is described by the relation
10
V n d d
where :
V = interstitial velocity of the groundwater
V = velocity of the relative concentration Ç/C = 0.5 in the c o
concentration front
p, = bulk mass density b
n = effective porosity
K, = distribution coefficient d
R, = retardation factor d
First-order decay is not incorporated in the model but can be
added to the model if desired. This can be done very easily as is
illustrated in the description of the model (PRICKETT et al., 1981,
p.14). The particle mass (PM) is then decreasing according to
PM = PM (0.5) T I M E / H L
o
where:
PM = particle mass at TIME=0 o
HL = half-life of the solute
The effect of dispersion can be illustrated with the progress
of a unit slug of tracer-marked fluid, placed initially at x=0,
in an infinite column of porous medium with steady flow in the
x-direction (no adsorption, no decay). BEAR (1972) describes the
solution as:
c ( x '° = (w1 vO* exp
Li
(x-Vt)2
4d Vt Li
(1)
where :
C = concentration
d = longitudinal dispersivity JLi
V = interstitial velocity
t = time
x = distance along the x-axis
11
The shapes of the curves C (x',t) are shown in fig. 2 where
x' = x-Vt.
M/n= 1.0
0.8
4 0.6
c
0.4
02
0 ^ /
\ " t o
W*
t 2 > t 1
I I After Bear, 1972
, t 3 > t 2
-5 -3 -2 -1 0 1 x' = x-Vt
Fig. 2. Progress of a slug around the mean flow
Based upon statistical concepts a random variable x is said
to be normally distributed if its density function, n(x) is given
by
n ( x ) • moexp (x-u)
- 2a2
2-(2)
where:
a = standard deviation of the distribution
u = mean of the distribution
Comparing both equations (1) and (2) it can be seen that these
equations are equal if:
a = /2dT Vt' Li
u = Vt
n(x) = C(x,t)
12
This means that dispersion in a porous system can be considered
as a random process with a normal distribution. This concept is not
new. Only the method by which this statistical approach is treated
in the computer code and is applied to transport problems is new.
In the computer a particle is moved in the flow direction x- and
y-direction during a time increment, DELP, by convection according
to its velocity (V ,V ). Then a random movement both in the flow J x' y
direction and in a direction transverse to the mean flow is added
to represent the effects of longitudinal and transverge dispersion.
This random movement is given the magnitude (see fig. 3): - in the x-direction: /2d DX * ANORM(O)
- in the y-direction: /2d DY * ANORM(O) J-j
- in the direction transverse to the flow: /2d„ DD * ANORM(O)
= v ^ T ™2 T where DD = VDX + DY , DX = V * DELP, DY = V * DELP
' x ' y
The function ANORM(O) is generated in the computer code as
a simple function involving a summation of random numbers. ANORM(O)
is a number between +6 and -6, drawn from a normal distribution of
numbers having a standard deviation of 1 and a mean of 0.
If the above process is repeated for numerous particles, all
having the same initial position (xx, yy) and convective term, the
new positions are normally distributed around the new position
(xx + DX, yy + DY).
The program can simulate one- or two-dimensional nonsteady/
steady flow problems in heterogeneous aquifers under watertable
and/or artesian or leaky artesian conditions. Furthermore this
program covers time-varying pumpage or injection from or into wells,
natural or artificial recharge rates, the relations of water
exchange between surface waters and the groundwater reservoir,
the process of groundwater évapotranspiration, the mechanism of
possible conversion of storage coefficients from artesian to water
table conditions and the mechanism of flow from springs.
It is possible to replace the hydrological part of the program
(i.e. PLASM) by another hydrological model if necessary.
13
(A) LONGITUDINAL DISPERSION
d L > 0
dT = 0
Old particle )ositior xx.yy
position \
*- x
DY = Vy»DELP
DD = y/0X2 + DY
DX = V
V^L=V5d[DD
V ^ v Jt> DISPERSE { RL»DD <*DELPX^£
RL*DY y > »-»- New particle position
y RL*DX
Where: xx.yy
RL*DD = v/2dLDD ANORM (0)
New position = Old position + Convection + Dispersion xx xx + DX + RL*DX yy = yy + DY + RL*DY
(B) TRANSVERSE DISPERSION
:erc DISPL = 10 - 3 0 )
Old particle _ DX = VX*DELP
position
d L = 0 (to avoid a zero divide in code
d T > 0
DD = , / D X 2 + DY2
Where:
RT*DD= x /2dTDD ANORM (0)
New position = Old position + Convection + Dispersion xx xx + DX + RT»DY yy yy + DY — RT*DX
Fig. 3. General scheme for convection and longitudinal (A) and
transverse (B) dispersion
14
3.3. L i t e r a t u r e
MERCER, JAMES W. and CHARLES R. FAUST, 1981. Ground-Water Modeling.
Geo Trans, Inc., P.O.Box 2550, Reston, Virginia (Copyright:
National Water Well Association)
PRICKET, T.A. and C G . LONNQUIST, 1971. Selected digital computer
techniques for groundwater resource evaluation. 111. State
Water Survey, Urbana, Bulletin 55
;r.G. NAYMIK and C G . LONNQUIST, 1981. A 'Random-Walk' solute
transport model for selected groundwater quality evaluations.
111. State Water Survey, Champaign. Bulletin 65
4. SOLID AND HAZARDOUS WASTE RESEARCH DIVISION, EPA (Cincinnatti, OH)
4 . 1 . G e n e r a l
This division of the Municipal Environmental Research Laboratory
is responsible for developing new and improved technology and methods
for:
- collection, transportation, processing and disposal of both solid
and hazardous wastes;
- prevention, control and abatement of accidental discharges of oil
and hazardous materials.
The division's research provides the scientific base for regulations
and standards required by the Resource Conservation and Recovery
Act. To perform its task the division uses research contracts,
grants and interagency agreements. Major programs include:
- improving landfill site selection and operation;
- investigating alternatives to landfills;
- recovery and reuse of waste materials;
- development of hazardous and oil spill technology.
In the past research was mainly focussed on municipal solid
waste. A large number of reports have been published on subjects
like production and quality of landfill leachate and landfill gas,
stabilization of landfill processes, recirculation of leachate
attenuation and migration of pollutants in soils near landfill sites.
15
This means that much information is available now, especially
on environmental effects of handling and disposal of municipal solid
waste at landfill sites. Recently the research in this field has
been gradually reduced and attention is now focussed on hazardous
waste materials.
Important areas of research are now:
- identification of pollutants in waste materials;
- generation and migration of pollutants;
- control and treatment of pollutants;
- closure of landfill sites;
- cost studies ;
- publication of technical handbooks.
4.2. G r o u n d w a t e r p o l l u t i o n n e a r l a n d f i l l s
A special problem is the characterization of hazardous waste
materials and the determination of leaching characteristics. For this
purpose leaching tests have to be done in the laboratory.
Standard leaching tests are available that prescribe leaching
of the waste material with acidified water. However, EPA is convinced
that these tests don't simulate the leaching process under field
conditions in a correct way. Therefore leaching tests with tap water
are preferred.
The same problem is met when studying the transport of pollutants
in soil with help of soil column experiments. In the USA many column
experiments have been done with pure solutions to determine adsorption
isotherms. The application of these isotherms in field situations
is far from realistic because the ionic strength and the presence
and concentration of competing ions may be completely different.
Therefore column experiments for a certain field situation should
be done with the waste water and soil type for that particular case.
An important research project is also the chemical stabilization
of hazardous waste and sludges. Several processes can be used to
encapsulate the hazardous waste, but only a few can stand the
durability tests (freezing/thawing, wetting/drying). The stabilized
material was also tested by leaching it with water during two years.
16
The best, but most expensive stabilization process approved to be
encapsulation with plastic.
Models are available to predict the leachate volume as a function
of climatical data, nature of vegetative cover and soil cover. Other
models predict the migration of pollutants in groundwater (both simple
analytical solutions and more complex computer models). Recently
EPA published a comprehensive report on methods which are available for
the prediction of leachate plume migration and mixing.
Density flow, which may occur under field conditions because of
the high density of the leachate, is not included in these models.
In only one case there was a slight indication that density flow
might have influenced the migration of pollutants. However, this
aspect does not get much attention in the USA.
4.3. L i n i n g a n d c a p p i n g o f l a n d f i l l s
Another aspect, which gets a lot of attention, is the lining and
capping of landfills to prevent infiltration of rain water and ground
water pollution. Research is going on about the durability of liners
in contact with leachate or organic liquids. Before application in
a certain field situation synthetic materials must be tested on
resistance against the leachate of that particular site. The tests
should run for 120 days at a temperature of 20°C. The changes in
physical features of the material are measured and should be less
than a prescribed percentage depending on the requirements for that
particular application. There is also research going on on the
longterm effects of leachate and organic liquids on the permeability
of clay liners (see Chapter 9).
Liners of clay should have a saturated conductivity less than -9 -1 . .
10 m.s , which is an order of magnitude lower than the limit used
in Germany. Compared with research data in the Netherlands the limit - 9 - 1 . . .
of 10 m.s is, however, still too high, since hydrological calculations and measurements have shown that the annual leakage through such clay
-1 layers may be in the order of 100 mm.year
A slightly different approach is the research which has been done on
liners of natural porous soils with the intention to minimize the
17
pollutant migration. In this case soils are selected on the base of
their attenuation capacity. Especially a high adsorptive capacity
for heavy metals is considered to be important. The permeability
of these liners is of less importance.
4.4. P r o d u c t i o n a n d r e c o v e r y o f l a n d f i l l
g a s
Another research project that has got much attention in the past
years is the production and recovery of landfill gas. Compared with
the situation in the Netherlands the composition of the municipal
refuse in the USA is quite different. There is much more paper (42%)
in the refuse, while the amount of food waste is minimal (12%)
because most kitchen waste is dumped in the garbage grainder and
goes into the sewage system.
Several reports have been published dealing with the following
aspects (see also Chapter 10):
- rate of decomposition and gas production (accelleration of processes
in a landfill) ;
- recovery of landfill gas (piping system, pumps, etc.);
- prevention of problems caused by horizontal spreading of the gas.
4.5. T h e CECOS l a n d f i l l f o r d i s p o s a l o f
h a z a r d o u s w a s t e
A field trip was made to the CECOS (Chemical and Environmental
Conservation Systems) landfill (211 acres), where hazardous waste
(a.o. PCB's) is deposited in a controlled way. The amount of hazardous
waste in the USA amounted to 50 x 10 tons in 1980, this figure will
rise to 85 x 10 tons in 2000.
The landfill was lined with a 60 mil (= 1.5 mm) high density
Polythylene liner. Both below (1.50 in) and above (0.60 m) the liner
a clay layer was brought in to protect the liner and to present
additional resistance against leakage. The clay layers were compacted -9 -1 to lower the saturated conductivity to a value as low as 10 cm.s
The waste is placed in the fill both as bulk material and in containers.
Ultimately the fill will be closed with a 20 mil (=0.5 mm) PVC-liner
18
between two layers of each 0.60 m of compacted clay. On top 6 inches
of top soil with grass will be placed.
Each firm, that wants to deliver waste at the site, has to fill
in a form reporting the characteristics of the waste. Furthermore
the quality of the waste is checked when it is delivered at the
site. For this purpose their is a laboratory at the site. The
containers are covered with soil, while the locations are indicated
on a map. The latter is important with respect to possible reclamation
of the waste in the future,
4 . 6 . L i t e r a t u r e
ANONYMUS, 1980. Guide to the disposal of chemically stabilized and
solidified waste. EPA-report (draft version), EPA, Mun.
Env. Res. Lab., Cincinnatti, OH
ANONYMUS, 1981. Management of uncontrolled hazardous waste sites.
Proc. Nat. Conf., Washington, D.C., October 28-30, 1981
COIA, M.F., J.J. PEIRCE and P.A. VESILIND, 1982. Impact of waste
chemicals on permeability of clays. Paper submitted for
publication in: J. Env. Eng. Div.
DAVIDSON, J.M., P.S.C. RAO, L.T. OU, W.B. WHEELER and D.F. ROTHWELL,
1980. Adsorption, movement and biological degradation of
large concentrations of selected pesticides in soils.
EPA-600/2-80-124, EPA, Solid and Hazardous Waste Res. Div.,
Cincinnatti, OH
DAY, M.E., 1970. Brine disposal pond manual. US Dept. of the
Interior Bureau of Reclamation, (only list of contents)
DIETRICH, T., 1978. Determination of permeability of mineral waste
deposit bases at low hydraulic gradients, (translation from
German). Forschungsbericht 78-102 02 019, Lab. Grundbau
und Bodenmechanik, Berlin
EPA, 1982. Project information sheets for hazardous materials
spills research. Mun. Env. Res. Lab., Oil and Hazardous
Materials Spills Branch, Edison, New Yersey
1982. Remedial action program. Mun. Env. Res. Lab., Solid
and Hazardous Waste Res. Div., Cincinnatti, OH
19
EPA, 1982. Handbook for remedial action at waste disposal sites.
EPA-625/6-82-006, Mun. Env. Res. Lab., Cincinnatti, OH
FARMER, W.J., M.S. YANG, J. LETCY and W.F. SPENCER, 1980. Land
disposal of hexachlozobenzene wastes: Controlling vapor
movement in soil. EPA-600/2-80-119, EPA, Solid and Hazardous
Waste Res. Div., Cincinnatti, OH
FULLER, W.H., 1981. Liner of natural porous materials to minimize
pollution migration. EPA-report, Solid and Hazardous
Waste Res. Div., Cincinnatti, OH
GIBB, J.P., R.M. SCHULLER and R.A. GRIFFIN, 1981. Procedures for
the collection of representative water quality data from
monitoring wells. Coop. Groundwater Report 7. 111. State
Water Survey & 111. State Geol. Survey, Champaign, 111.
GRIFFIN, R.A. and N.F. SHIMP, 1978. Attenuation of pollutants in
municipal landfill leachate by clay minerals. EPA-600/2-
-78-157, EPA, Solid and Hazardous Waste Res. Div., Cincinnatti,
OH
HAM, R.K. et al., 1979. Recovery, processing and utilization of
gas from sanitary landfills. EPA 600/2-79-001, EPA, Solid
and Hazardous Waste Res. Div., Cincinnatti, OH
JAMES, S.C. and C.W. RHYNE. Methane production, recovery and
utilization from landfills. EPA, Solid and Hazardous Waste
Res. Div., Cincinnatti, OH
KENT, D.C., W.A. PETTYJOHN, T.A. PRICKET and F.E. WITZ, 1982.
Methods for the prediction of leachate plume migration.
EPA-report (draft), EPA, Solid and Hazardous Waste Res.
Div., Cincinnatti, OH
LUDWIQSON, J., 1982. Hazardous Material Spills Conference Proceedings.
Milwaukee, Wisconsin, April 19-22, 1982
LUTTON, R.J., 1982. Evaluating Cover Systems for solid and hazardous
waste. EPA-report (draft version), EPA, Solid and Hazardous
Waste Res. Div., Cincinnatti, OH
, G.L. REGAN and L.W. JONES, 1979. Design and construction
of covers for solid waste landfills. EPA-600/2-79-165,
EPA, Solid and Hazardous Waste Res. Div., Cincinnatti, OH
20
MIDDLEBROOKS, E.J., C D . PERMAN and I.S. DUNN, 1978. Wastewater
stabilization pond linings. Special Report 78-28, Middlebrook
and Ass., Logan, Utah, 121 pp
MOORE, C.A., 1980. Landfill and surface impoundment performance
evaluation manual. EPA-report (draft version), EPA,
Mun. Env. Res. Lab., Cincinnatti, OH
PETTYJOHN, W.A., D.C. KENT, T.A. PRICKETT, H.E. LEGRAND and F.E. WITZ,
1982. Methods for the prediction of leachate plume migration
and mixing. EPA-report (draft), EPA, Mun. Env. Res. Lab.,
Cincinnatti, OH
ROSS, D.E. et al., 1978. Study of engineering and water management
practices that will minimize the infiltration of precipitation
into trenches containing radioactive waste. ORP LV-78-5,
EPA, Off. Radiation Programs, Las Vegas
SHUCKROW, A.J., A.P. PAJÄK and C.J. TONHILL, 1982. Management of
hazardous waste leachate. EPA-report (draft), EPA, Mun.
Env. Res. Lab., Cincinnatti, OH
SHULTZ, D.W., 1982. Land disposal of hazardous waste. Proc. Eight
Annual Research Symposium, EPA-600/9-82-002, EPA, Cincinnatti,
OH
STRAUB, W.A. and D.R. LYNCH, 1982. Models of landfill leaching:
Moisture flow and inorganic strength. J. Env. Eng. Div.
108 (No. EE2): 231-268
TOLMAN, A.L., A.P. BALLESTERO, W.W. BECK and G.H. EMRICH, 1978.
Guidance manual for minimizing pollution from waste disposal
sites. EPA-600/2-78-142, US. Env. Protection Ag.,
Cincinnatti, 83 pp
WANG, M.C., 1981. Lining methods and compacted soil liner for
reserve pit/tailings pond - A review. US Geol. Survey,
Reston, VA
ZASLAVSKY, D., 1980. Specification for sealing of earth reservoirs
by non-continuous plastic membranes. Publ. No. 314,
Israel Inst. Techn., Technion, Haifa, Israel
21
5. SYMPOSIUM ON AQUIFER RESTORATION AND GROUNDWATER MONITORING
(Columbus, OH)
5.1. G e n e r a l
This Conference was meant to give a overview of the measures
which can be taken in case of serious groundwater contamination.
A lot of accidental spills and serious pollution problems were
reported. In most cases measures had to be taken within a couple
of days to weeks. A general impression of the Conference is that
there is already a lot of experience with various restoration
measures in the USA, but research concerning the effectiveness of
such measures is still in its infancy.
Measures to contain or remove contaminated groundwater include:
- construction of withdrawal wells, interceptor wells or trenches;
- surface capping to prevent infiltration of rainwater;
- construction of impermeable vertical walls with bentonite, grout
columns or sheet piles;
- immobilization of contaminants in the soil.
Special attention was also given to the sampling and analysis
of groundwater and the application of models to calculate the migration
of contaminants in groundwater.
5.2. W i t h d r a w a l a n d i n t e r c e p t o r w e l l s
In case of serious aquifer contamination one of the first
solutions considered is withdrawal of the contaminated groundwater.
The position of extraction wells, the monitor well spacing with
respect to the extraction wells and the duration and rate of
extraction (and perhaps injection of the treated groundwater)
should be designed with help of hydraulic computer models that
consider also anisotropic properties of the aquifer system.
A few papers discussed the effect of adsorption processes
on the flow of a contamination front. This effect should be realized
in designing monitoring networks, including distribution of wells
and well depths. Due to adsorption processes the amount of water,
which has to be removed from a contaminated aquifer, is much greater
22
for an adsorbing species than would be required for a non-adsorbing
species. Furthermore the adsorption process may not be reversible,
which means that the desorption process may take much more time
than would be predicted on the base of adsorption curves only.
Hydrocarbons which are lighter than water, float on the
groundwater. Techniques for recovery of lost product and the
abatement of residual, dissolved hydrocarbons may include the
recovery of free product by a special two-pump system or with
intercepting trenches. The groundwater extracted should be treated.
The removal of dissolved hydrocarbons can be done by air stripping
(especially effective for low molecular compounds if the distribution
ratio C . /C is higher than 10), by activated carbon filters air water & ' J
(for removal of high molecular compounds) or by biochemical processes.
5.3. S u r f a c e c a p p i n g
In the USA the permeability limit for clay caps on top of a - 9 - 1 .
landfill is set at 10 m.s . The clay cap is meant to reduce
infiltration of rainwater. The ICW has done research in the Netherlands
indicating that this permeability limit is too high for the Dutch
climatic conditions. The annual leakage through such clay barriers
is about 100 mm per year (i.e. one third of the annual precipitation
surplus).
Since there are large differences in climate between the states
in the USA such clay caps may give sufficient protection in states
with relatively low amounts of rainfall but they will definitely
give insufficient protection in states with a more wet climate.
5.4. I m p e r m e a b l e v e r t i c a l w a l l s a n d
i m m o b i l i z a t i o n o f c o n t a m i n a n t s
Vertical walls or dams are especially suitable when the
aquifer is rather shallow. Such barriers may be constructed with
bentonite, grout or sheet piles. One case was reported where
suitable clay was present at the landfill site. The clay was remolded . . -10 -1
to a permeability of 3 x 10 m.s and placed in an excavated
23
trench to the bottom of the aquifer (about 5 to 7 meter).
Vertical barriers were found to be effective only when the
depth of the barrier was equal to the depth of the aquifer. Several
case studies were reported illustrating measures which were taken
to prevent further migration of contaminants in the groundwater,
e.g. serious pollution near a hazardous waste landfill was abated
with clay barriers, subsurface grout curtains and interceptor wells.
One paper reported a unique method of containment, viz. the
polymerizing of a contaminant in the soil. In this case the pollutant
was acrylate monomer, being lighter than water. The hydrogeologic
conditions did not favor recovery by conventional techniques.
Therefore catalysts were injected to immobilize the contaminant
by polymerization. The effectiveness of such immobilization methods
should be investigated more thoroughly.
5.5. T h e u s e o f c o m p u t e r m o d e l s
Excercises with computer models should be incorporated in a
groundwater restoration project right from the start, because it can
give valuable information about data collection and the design of
monitoring networks, extraction and injection wells, etc.
Two numerical models were discussed during the Symposium.
One model (TRANS, finite differences) was used for the horizontal
spreading of contaminants in an aquifer, while the other model
(finite elements) was used for the calculation of contaminant
transport in the vertical plane. The effect of density flow was found
to be small, but this was mainly due to the effect of a rather high
transverse dispersion coefficient.
Another paper presented an analytical solution for the two-
dimensional horizontal plane, taking into account dispersion.
With respect to model calculations a warning was given, that
the results of models can never be more exact than the input data.
Especially with complex numerical models a lot of parameters are
needed. Often these parameters are insufficiently known. In such
cases the use of more simple models and analytical solutions may be
considered to give rough estimates.
24
5.6. S a m p l i n g o f g r o u n d w a t e r
Another session at the Conference was the sampling and analysis
of groundwater.
The importance of sampling at different depths and placing seals
between screens of different height was stressed because of the
vertical concentration variation in aquifers.
For several parameters groundwater samples should be collected
in vessels which retain in situ pressure conditions until laboratory
analysis are performed. Sampling techniques and sampling materials
used should be selected considering the specific purpose for which
they are intended. This is important to avoid:
- loss of volatiles due to evaporation;
- loss or gain sample constituents from adsorption or leaching
from sample equipment;
- introduction of contaminants carried by sampling equipment.
For the analysis of volatile organics suction lifting with a
pump has to be avoided. In this case a sampling syringe should be
used. Because of possible alterations in the sample the possibility
for measurements in the bore hole should be considered.
The materials used for sampling wells, pumps, sample vessels
etc. may affect the waterquality. When choosing a material, the
parameters to be analyzed should be taken into account. Materials
like teflon and stainless steel are the most inert materials.
The volume of water, which has to be removed from the borehole
before sampling, should be determined by measuring the electrical
conductivity and the temperature of the water. Sampling can be
performed as soon as these values have become constant.
A lot of papers discussed the design and installation of
monitoring wells. Important factors are: drilling and installation
method, construction materials, single or multiple screens,
decontamination of equipment and materials, and prevention of
cross - contamination by perforation of impermeable barriers.
25
5.7. L i t e r a t u r e
GIBB, J.P., R.M. SCHULLER and R.A. GRIFFIN, 1981. Procedures for
the collection of representative water quality data from
monitoring wells. Coop. Groundwater Rep. 7, 111. State Water
Survey & 111. State Geol. Survey, Champaign, 111.
KAUFMANN, R.F., T.A. GLEASON, R.B. ELLWOOD and G.P. LINDSEY, 1981.
Groundwater monitoring techniques for arid zone hazardous
waste disposal sites. Reprint from: Groundwater Monitoring
Review, Fall 1981
NAYMIK, T.G. and M.J. BARCELONA, 1982. Characterization of a
contaminant plume in groundwater, Meredosia, Illinois.
Groundwater 19: 517-526
PROCEEDINGS of the Second National Symposium on Aquifer Restoration
and Groundwater Monitoring, May 26-28, Columbus, Ohio (1982)
REHTLANE, E.A. and F.D. PATTON, 1982. Multiple port piezometers
US. standpipe piezometers: an economic comparison. Sec. Nat.
Symp. 'Aquifer Restoration and Groundwater Monitoring',
Columbus, OH
SVENDLEIN, L.V.A. and H. YAZICIGIL, 1981. Surface geophysical
techniques in groundwater monitoring (Part I). Reprint from:
Groundwater Monitoring Review, Fall 1981
YAZICIGIL, H. and L.V.A. SENDLEIN, 1982. Surface geophysical
techniques in groundwater monitoring (Part II). Reprint
from: Groundwater Monitoring Review, Winter 1982
26
6. GEORGIA INSTITUTE OF TECHNOLOGY (Atlanta, GA)
6.1. G e n e r a l
The Georgia Technology Institute (or briefly Georgia Tech.) is
a technical highschool, where students from all over the country
and from abroad are pursuing undergraduate and graduate degrees in
engineering, architectural, scientific and management schools and
colleges. The study in Environmental Engineering provides education
and research in the fields of water quality and pollution control, air
quality and pollution control,solid and hazardous waste management,
and environmental sciences.
Within the School of Civil Engineering research is done on
environmental aspects of disposal of solid and hazardous waste in
sanitary landfills, sludge treatment and disposal, biological,
physical and chemical treatment and water quality modeling.
6.2. S t a b i l i z a t i o n p r o c e s s e s i n a l a n d
f i l l
A lot of research has been done on stabilization processes in
a landfill and the enhancement of this process by leachate
recirculation. Because of smell problems the leachate is not recirculated
by sprinkler irrigation but via an underground drainsystem.
Several papers have been published on this subject (e.g. POHLAND,
1975, 1980) demonstrating that collecting and recirculating leachate
through a landfill dramatically decreases time required for stabilization
of the anaerobic bacterial population. Rapid stabilization is wanted
because the potential of environmental pollution is minimized in that
case. The organic load of the leachate strongly reduces by methane
fermentation within the landfill. Moreover the leaching of heavy
metals reduces because the pH rises and the metals are precipitated
as poorly soluble sulfides. As soon as stabilization is reached the
landfill should be covered with an impermeable liner.
The research on stabilization showed that the cumulative gas 3
production was very low, about 7 m per ton of refuse. Probably the
27
gasproduction proceeds very fast. The rapid reduction in gas production
after stabilization was ascribed to limitation of the bacterial process
by phosphate shortage.
For the experimental setup columns of various dimensions are used.
In the laboratory containers of about 200 liter are used. Outside
the laboratory in the open air pilot-scale landfill cells of about
3 meter height and 1 meter diameter are used. Furthermore lysimeters 2 .
of about 4 meter depth and 9 m in cross section are present here.
6.3. C o d i s p o s a l o f l o w - l e v e l r a d i o a c t i v e
w a s t e a n d m u n i c i p a l r e f u s e
Based on the results of the stabilization research a study is
now going on on codisposal of low-level radioactive wastes with
municipal solid waste in landfills. In the laboratory experiments
were done with shredded refuse in polyethylene containers (contents
208 liters). The radio-active isotopes used in this study were
Co-58, Cs-134 and Sr-85. In addition tritium (H-3) was added as a
tracer of water for the determination of water migration and its
role in biological conversion.
Both the leachate and gas generated in the containers were
collected and analyzed for its quantity and composition. The effect
of leachate recirculation was tested. In approximately six months
stabilization was reached. Especially Co-58 was effectively contained
in the waste, presumbably in the form of metal sulfides. The
containment of Cs-134 and Sr-85 was considerably smaller.
Tritium was present in the gas produced, probably as a result 3 . 3
of conversion of H„0 into C H, . Therefore biogas produced in
landfills containing tritium would require treatment to eliminate
radiation hazards.
Based on these early results it was stated that codisposal of low-
level radioactive wastes and municipal solid waste may be a promising
means of disposal because the radionuclides are transformed to poorly
soluble sulfides and probably also carbonates. However, the degree
of containment was not equally effective for all radionuclides used in
this study. Especially the radioactivity of Sr-85 remained relatively
high in the leachate. Nevertheless this method of codisposal is
recommended as a promising one.
28
6.4. I d e n t i f i c a t i o n a n d c h e l a t i n g e f f e c f
o f o r g a n i c p o l l u t a n t s
Another interesting research project at Georgia Tech is a study
on identification of organic pollutants in landfill leachate,
especially the identification of humic compounds. Techniques used for
isolation and concentration of organics are: centrifugation, millipore
filtration, membrane ultrafiltration, reversed osmosis, XAD-resins,
and gel permeation. For the detection of organic compounds techniques
like gas chromatography, infrared spectroscopy (IR) and mass spectro
photometry (NMR) are used.
For the analysis of organic micropollutants it is very important
to use inert materials for sampling equipment, sample bottles, tubes,
valves, etc. Teflon and glass have proven to be the most inert
materials. Other materials may adsorb or release organic compounds.
The glass materials are pretreated at 450°C to destroy all organics.
The nature of the organic compounds in landfill leachate reflects
the degree of stabilization. After stabilization there are no volatile
fatty acids left in the leachate. The organics present in stabilized
leachate are mainly humic compounds.
The aspect of complex formation of heavy metals and organic
compounds is also studied at Georgia Tech. A standard test for the
chelating effect of humic compounds is to establish whether or not
the concentration of heavy metals in a solution with humic compounds
is higher than in a solution without these compounds. Stability
constants for these metal complexes are both calculated and
experimentally determined.
The identification techniques are also applied to research on
removal of organics from water by various purification techniques and
control of the efficiency of these techniques.
6 . 5 . L i t e r a t u r e
CHANG, K., E.S.K. CHIAN, F.G. POHLAND, B. KAHN, Q.H. CROSS and
L. ROLAND, 1982. Codisposal of low-level radioactive wastes
within sanitary landfills. (Paper submitted for a symposium)
29
CHENG, S.S. and E.S.K. CHIAN, 1982. Treatment of phenol with an
innovative fluidized bed activated carbon anaerobic filter
(paper submitted for publication)
CHIAN, E.S.K. and F.B. DE WALLE, 1976. Sanitary landfill leachates
and their treatment. J.Env.Eng.Div. 102 (No. EE2): 411-431
and F.B. DE WALLE, 1977. Evaluation of leachate treatment.
EPA-600/2-77-186a, EPA, Solid and Hazardous Waste Res. Div.,
Cincinnatti, OH
et al., 1982. Anaerobic treatment of firefighting wastewater
(paper submitted for publication)
CLARK, R.R., E.S.K. CHIAN and R.A. GRIFFIN, 1979. Degradation of
polychlorinated biphenyls by mixed microbial cultures.
Appl. Env. Microb. 37:680-685
DE WALLE, F.B., E.S.K. CHIAN and E. HAMMERBERG, 1978. Gas production
from solid waste in landfills. J. Env. Eng. Div. 104(No.EE3):
415-432
and E.S.K. CHIAN, 1978. Solid wastes and water quality
(literature review). J. Water Poll. Control Fed. 50: 1277-1286
and E.S.K. CHIAN, 1979. Solid wastes and water quality
(literature review). J. Water Poll. Control Fed. 51: 1402-1410
, E.S.K. CHIAN and J. BRUSH, 1979. Heavy metal removal with
completely mixed anaerobic filter. J. Water Poll. Control
Fed. 51: 22-36
and E.S.K. CHIAN, 1980. Solid wastes and water quality
(literature review). J. Water Poll. Control Fed. 52: 1494-1506
and E.S.K. CHIAN, 1981. Detection of trace organics in well
water near a solid waste landfill. Res. and Techn., Journal
AWWA, April 1981: 206-211
, D. NORMAN, J. SUNG and E.S.K. CHIAN, 1981. Analysis of
Chemical Species: Organic. J. Water Poll. Control Fed.
53: 659-674
et al., 1982. Presence of phenolic compounds in sewage
effluent and sludge from municipal sewage treatment plants.
Water Sei. Techn. 14: 143-150
30
GHOSAL, M., J.H. REUTER, E.S.K. CHIAN and L. GELBAUM, 1982. Use
of field-variation and double irradiation techniques in
structural study of aquatic humic substances. Report
School of Civil Eng., Georgia Tech.
LEE, M.C., E.S.K. CHIAN and R.A. GRIFFIN, 1979. Solubility of
polychlorinated biphenyls and capacitor fluid in water. Water
Res. 13: 1249-1258
, R.A. GRIFFIN, M.L. MILLER and E.S.K. CHIAN, 1979.
Adsorption of water-soluble polychlorinated biphenyl
Aroclor 1242 and used capacitor fluid by soil materials and
coal chars. J. Env. Sei. Health, A14(5): 415-442
LEENHEER, J.A., 1981. Comprehensive approach to preparative isolation
and fractionation of dissolved organic carbon from natural
waters and waste waters. Env. Sei & Techn. 15: 578-587
POHLAND, F.G., 1980. Leachate recycle as landfill management option.
J. Env. Eng. Div. 106: 1057-1069
REUTER, J.H., M. GHOSAL, E.S.K. CHIAN and M. GIABBAI, 1982. Oxidative
degradation studies on aquatic humic substances, (paper
submitted for publication)
TITTLEBAUM, M.E., 1982. Organic carbon content stabilization through
landfill leachate recirculation. J. Water Poll. Control Fed.
54: 428-433
31
7. DEPARTMENT OF SOIL AND CROP SCIENCES (A & M University,
College Station, TX)
7.1. G e n e r a l
The research program of the Department of Soil and Crop Sciences
is mainly agriculture-oriented. This means that physical and chemical
features of soils are studied in relation with crop production.
Especially water supply of crops is an important research subject
because of shortness of water during the growing season.
Part of the research program, however, deals with subjects
that are related with non-agricultural activities, either because
these activities may have consequenses for agriculture like land
application of sewage effluent, sewage sludge and oily sludges,
or because special knowledge present here can be applied to solve
certain non-agricultural problems.
7.2. E f f e c t o f l i q u i d w a s t e o n c l a y l i n e r s
One of the non-agricultural problems studied here is the effect
of liquid waste on the permeability of clay liners. In the USA clay
liners are used in landfills for containment of both municipal refuse
and hazardous waste. The permeability of such clay liners has to be -9 -1
less than 10 m.s
Although EPA has banned the disposal of containerized liquids
in landfills, there is evidence that several containerized organic
liquids are still placed in landfills, either as a liquid or adsorbed
on a solid matrix. The latter is still permitted but the concentrations
may exceed the retention capacity of the solid matrix. When such
containers with hazardous liquid waste are present in a landfill it
is possible that on the long run containers may loose their contents.
The liquid waste may then contact the clay liner.
Laboratory investigations were performed to test the permeability
of clay liners with four classes of pure organic liquids, i.e. acidic
(acetic acid), basic (aniline), neutral polar (methanol, acetone,
ethylene glycol) and neutral non-polar (heptane, xylene) organic
fluids. The results were compared with a standard aqueous solution
32
(0.01 N CaSO,). The clay soils tested were non-calcareous smectite,
calcareous smectite, mixed cation kaolinite, and mixed cation illite.
It was found that the low permeability of compacted clay liners,
as tested with an aqueous solution of 0.01 N CaSO,, may substantially
increase when tested with organic fluids. Only a minor part of the
increase could be explained by the different density to viscosity
ratio of the organic fluids. Other explanations for the increase
in permeability are: dissolution of soil particles followed by
soil piping (with acetic acid), extensive structural changes or
excessive shrinkage and cracking (aniline, acetone, methanol, xylene,
heptane). Often the change in permeability was found to be more than
two orders of magnitude.
The results of these laboratory investigations indicate that
clay liners should be tested with the leachate to which they will
be exposed. The research is going on now both with laboratory
experiments and field experiments in lysimeters.
Twenty-eight lysimeters have been constructed in the field,
each consisting of an under-drain system and a compacted clay liner
(montmorillonite, illite and kaolinite). Leaking barrels of dye
labelled industrial wastes, containing primarily either acetone or
xylene, have been placed on the clay liners and were covered with
soil. Leachate from the under-drain system has been collected and
analyzed to establish the leakage rate and the presence of organic
fluids.
Later on the clay liner has been investigated for any physical
or chemical changes. This was done with the technique of thin
sections. In this way much information has been obtained about the
structural changes in the clay liners. In general the results of
the laboratory experiments were confirmed by the field experiments.
7.3. M o d e l i n g o f g r o u n d w a t e r p o l l u t i o n
Another interesting subject of research in this Department
is the study of groundwater pollution from fertilizers or other
chemicals when applied to cropland, from manure produced by livestock
feedlots, and from disposal of domestic or industrial wastes on land.
33
For the purpose of predicting the transport of pollutants in
groundwater a three-dimensional model was developed describing the
two-phase (air-water) fluid flow equations in an integrated saturated-
unsaturated porous medium. The model describes the relationship
between infiltration of water and air movement in the unsaturated
zone. The infiltration rate significantly reduces when air is
trapped and cannot escape freely.
Also a three-dimensional convective-dispersion equation describing
the movement of a conservative, non-interacting tracer in a non-
homogeneous, anisotropic porous medium was developed using the
method of characteristics (MOC).
The two models have been linked together by the pore water
velocity term. The program listing is added to the report on this
model (KHALEEL and REDDELL, 1977).
The model was tested with different analytical solutions and
experimental data from infiltration experiments, including the
effect of trapped air on infiltration. The agreement with the
results calculated with the model was very good.
7.4. L i t e r a t u r e
ANDERSON, D., K.W. BROWN and J. GREEN, 1982. Effect of organic
fluids on the permeability of clay soil liners (paper
submitted for publication)
CRITES, R. et al., 1977. Process design manual for land treatment
of municipal waste water. EPA 625/1-77-008
KHALEEL, R. and D.L. REDDELL, 1977. Simulation of pollutant movement
in groundwater aquifers. Techn. Rep. No. 81, Water Res. Inst.,
A & M University, Texas, 248 pp
KNISEL, W.G., 1980. CREAMS: A field-scale model for Chemicals,
Runoff and Erosion from Agricultural Management Systems.
US Dept. of Agriculture, Cons. Res. Rep. No. 26, 640 pp
34
8. U.S. WATER CONSERVATION LABORATORY (Phoenix, AR)
8 . 1 . G e n e r a l
The US Water Conservation Laboratory is performing research
in the field of water supply to crops. Because of the arid climate
in Arizona (less than 200 mm annual rainfall) the main research
topics are:
- conservation of water sources
- distribution of irrigation water
- crop measurements to determine the need for irrigation
- water-climate-plant relations (both in the field and in glass
houses)
In the past years the use of groundwater has increased
tremendously resulting in a dramatical lowering of the groundwater
level. In certain areas the lowering of the groundwater level
amounts to tens of meters. Because of the shortness of water reuse
of sewage water is very attractive.
8.2. R e u s e o f s e w a g e w a t e r
Since 1967 research has been done here on land treatment of
secondary effluent of a sewage treatment plant with the aim to reuse
the renovated water for irrigation.
The land treatment is necessary to meet the EPA-standards with
respect to biochemical oxygen demand (BOD) and suspendid solids -1
(SS). Both values must be less than 10 mg.l , and the faecal coliform
concentration must be less than 200 per 100 ml. When these standards
are met the effluent can be used for irrigation of crops for human
consumption. Without this treatment the secondary effluent can only
be used for crops not intended for human consumption.
A large project, the Flushing Meadows Project, was started to
study the efficiency of land treatment, the construction and
operation of rapid-infiltration basins and the quality of the
renovated water pumped from the aquifer. There were six basins,
which were flooded intermittently with secondary sewage effluent.
35
Flooding and drying periods of a few days to several weeks were used.
During flooding periods the infiltration rate ranged from 0.3 to
1.0 m.day . The depth of the groundwater table averaged about 3 meter.
It was found that this rapid-infiltration system produced
renovated water that is suitable for unrestricted irrigation, even
at high loadings of 122 m.year . The removal of nitrogen and phosphorus
was respectively 30% and 40% increasing to 65% and 80% at a lower
hydraulic loading of 60 m.year
In 1978 the Flushing Meadows Project was destroyed by a severe
flood in the Salt River. The project was not restored. At this moment
the research is continuing at a large field scale in the 23rd Avenue
Project (four basins of 4 ha each). The renovated water is pumped
from a depth of 30-60 meter with three large-capacity pumps. This
water is used for unrestricted irrigation.
At a smaller experimental field the use of primary effluent
(only mechanically purified) was investigated. Since this water
contains more organic carbon denitrification is enhanced. Moreover
the costs for treatment in the sewage treatment plant are strongly
reduced, so it may be economically advantageous to use the primary
effluent.
Research on the behaviour of organic micropollutants indicated
that many compounds were significantly removed from the waste water
during infiltration. Nevertheless many organic micropollutants could
be detected in the groundwater. Therefore such infiltration projects
should be situated in areas, where the spreading of contaminants in
the aquifer will be restricted to a small area around the infiltration
point.
8.3. W a t e r h a r v e s t i n g a n d i r r i g a t i o n
Because of the dry climate research has been done on water
harvesting, i.e. the rain water from a relatively large area is
collected and used to supply crops in a smaller area with sufficient
water. For this purpose the soil surface is made impermeable, e.g.
with wax (parafin), NaCl (dispersion of clay) or bentonite clay,
in combination with an organic stabilizer (byproduct of the petroleum
36
industry). The surface runoff from this area is collected and used c
for irrigation in an other smaller area.
Irrigation has been and still is extensively studied in the
institute. In this respect the plant-water relationship and the
design of surface irrigation systems are investigated with special
emphasis on salinity problems and efficiency of irrigation.
Recently a lot of research has been done on constructing simple
measuring flumes for practical use in irrigation canals. In cooperation
with the International Institute for Land Reclamation and Improvement
in Wageningen a handbook will be published on this subject.
With the purpose to improve the water application efficiency
research is done on so-called level-basin irrigation. It involves
applying water to a level ground area surrounded by a dike. The
land is leveled by dragscrapers with help of laser beams to reach
a high degree of precision. If the system is properly designed, losses
of water are minimal, the mean depth of infiltration is rather
constant over the field (about 6-10 cm), and irrigation efficiencies
above 90 percent can be attained. Another advantage of this system
is that natural rainfall is not lost by surface runoff.
8.4. C r o p p r o d u c t i o n
The water status of a crop is a primary determinant of crop
yield. A lot of research has been done on measuring this water
status and determining the need for irrigation. Measuring leaf
temperatures is a means to evaluate the water status of a plant.
In the Water Conservation Laboratory remote sensing techniques are
used to determine leaf temperatures. One of the techniques used here
is measuring the leaf temperature with help of hand-held infrared
radiation thermometers. The data obtained are used together with
wet- en dry-bulb air temperatures and net radiation to calculate
the crop water stress index (CWSI). It appeared that the CWSI-
value is nearly linearly related to a number of crop functions.
It was concluded that the CWSI is a promising tool for quantifying
crop water stress, and it may be a useful tool as an irrigation
guide.
37
Another research project was the study on the effect of carbon
dioxide on crop production. A stimulating effect of C0? on crop
production was found both for raised CO„-levels in the rootzone
and for CO„-supply in the atmosphere.
To raise the CO„-level in the rootzone C0~ is solved in the
irrigation water which is supplied with a subsurface distribution
system. In glasshouses the CO„-content of the atmosphere can be
raised with help of gasburners.
At a CO~-level of 0.1% in the atmosphere the stomata are more
closed causing a more efficient use of water. The increase in crop
yield may amount to 30-50%.
8.5. L i t e r a t u r e
BOUWER, H., R.C. RICE, J.C. LANCE and R.G. GILBERT, 1980. Rapid
infiltration research at Flushing Meadows Project, Arizona.
J. Water Poll. Control Fed. 52: 2457-2470
^_ , M. REINHARD, P.L. McCARTY, H. BOUWER and R.C. RICE, 1982.
Organic contaminant behaviour during rapid infiltration of
secondary wastewater at the Phoenix 23rd Avenue Project
CLEMMENS, A.J. and J.A. REPLOGLE, 1980. Constructing simple
measuring flumes for irrigation canals. Farmers' Bull.
Nr. 2268, 13 pp
ERIE, L.J. and A.R. DEDRICK, 1979. Level-basin irrigation: a method
for conserving water and labor. Farmers' Bull. Nr. 2261,
23 pp
IDSO, S.B., R.D. JACKSON and R.J. REGIONATO, 1977. Remote-sensing
of crop yields. Science 196: 19-25
, R.D. JACKSON, P.J. PINTER, R.J. REGINATO and J.L. HATFIELD,
1981. Normalizing the stress-degree-day parameter for
environmental variability. Agric. Meteorology 24: 45-55
JACKSON, R.D., R,J. REGINATO and S.B. IDSO, 1977. Wheat canopy
temperature: A practical tool for evaluating water requirements.
Water Res. Res. 13: 651-656
, S.B. IDSO, R.J. REGINATO and W.L. EHRLER, 1977. Crop
temperature reveals stress. Crops and Soils Mag., June-July
1977: 10-13
38
JACKSON, R.D., S.B. IDSO, R.J. REGINATO and P.J. PINTER, 1981.
Canopy temperature as a crop water stress index. Water Res.
Res. 17: 1133-1138
KIMBALL, B.A. and S.T. MITCHELL, 1979. Tomato yields from CO.-enrichment
in unventilated and conventionally ventilated greenhouses.
J. Amer. Soc. Hort. Sei 104: 515-520
PINTER, P.J., M.E. STANGHELLINI, R.J. REGINATO, S.B. IDSO, A.D. JENKINS
and R.D. JACKSON, 1979. Remote detection of biological stress
in plants with infrared thermometry. Science 205: 585-587
and R.J. REGINATO, 1981. Thermal infrared techniques for
assessing plant water stress. Proc. Irrigation Scheduling
Conference, Chicago, IL.
PUBLICATIONS LIST OF THE US WATER CONSERVATION LABORATORY (857
publications)
39
9. MATRECON, I n c . (Oakland, CA)
9 . 1 . G e n e r a l
Matrecon, Inc. is a firm, formed in 1973, which provides research
and development, consulting, and testing services related to non-
metallic materials. Major areas of expertise are in:
- the science and technology of rubber and rubber products, asphalt
and other bituminous materials, and concretes
- evaluations of plastics, coatings, adhesives, and textiles
- utilization of industrial and agricultural byproducts and wastes
- erosion control and soil stabilization
- environmental science.
9.2. T e s t s o n l i n i n g m a t e r i a l s f o r l a n d
f i l l s
Matrecon, Inc. has been and is still conducting research on
lining materials for sanitary landfills and for the impoundment of
hazardous wastes. The materials tested include soils and soil cement,
asphalt concrete and membranes, and a wide range of polymeric membranes,
The tests included exposure of the materials to municipal solid
waste leachate and to selected hazardous wastes for 56 months in
landfill simulators. After this exposure the effects were measured
by establishing the changes in important physical properties of
the lining materials, e.g. tensile strength, elongation at break,
stress at 100% and 200% elongation, tear strength, puncture resistance
and hardness.
One of the best early indicators of incompatibility of a liner
and a waste is the change in weight or dimensions after an immersion
test, due to either swell or shrinkage.
Another promising test is the pouch test. Small pouches are
fabricated of the membrane material to be tested. These pouches
are filled with waste or other test fluids and immersed in deionized
water. The permeability of the membrane to water and pollutants is
determined by observing the change in weights of the pouch and by
measuring the pH and electrical conductivity of the deionized water.
40
Outdoor exposure tests with the liner materials
should be run to give information on the degree of deterioration by
ultraviolet light, heat and wind (degradation of the polymer, loss
of plasticizer). The materials were exposed for nearly 3$ years
(1231 days) on a roof rack.
In tub tests the membrane liners are exposed simultaneously
to the weather and to wastes. The liner is draped over a tub and folded
to fit the inside contours and edges. The excess material is allowed
to hang freely over the edges of the tub. The tubs are kept 5/8 to 7/8
full of wastes and the liquid level is allowed to fluctuate to test
the alternating effect of wetting and drying.
9.3. S e l e c t i o n o f l i n i n g m a t e r i a l s
The results of this research indicate that lining materials should
be carefully selected for specific wastes. Each lining material has
to be tested for the specific situation where it will be used.
Compatibility tests (exposure to samples of the waste fluid during
a period of minimal 6 months) should be part of the liner selection
process (immersion, pouch and tub tests).
Organic constituents in waste fluids were found to be particularly
important if organic-type lining materials are contemplated. Problems
like swell or shrinkage by adsorption of waste fluid or extraction of
plasticizer may be expected. That's the reason why oily wastes cannot
be safely contained with asphalt-based liners or non crystalline
polymeric membranes like rubbers and PVC. In a similar way bentonite
liners and clay soils may not be satisfactory for confining strong
acids and bases and concentrated brines.
9.4. L i t e r a t u r e
HAXO, H.E., R.S. HAXO and R.M. WHITE, 1977. Liner materials exposed
to hazardous and toxic sludges (First Interim Report) EPA,
Solidand Hazardous Waste Research Div ision, Cincinnatti, OH;
EPA-600/2-77-081, 63 pp
41
HAXO, H.E., R.S. HAXO and T.F. KELLOGG, 1979. Liner materials
exposed to municipal solid waste leachate (Third Interim
Report) EPA-600/2-79-038.EPA, Solid and Hazardous Waste
Res. Div., Cincinnatti, OH., 57 pp
, 1981. Testing of materials for use in the lining of waste
disposal facilities. Am. Soc. Testing Materials, Philadelphia;
Special Techn. Publ. 760: 269-292
PUBLICATIONS LIST OF MATRECON, Inc. on environmental projects
42
10. PACIFIC GAS AND ELECTRIC COMPANY (San Francisco, CA)
10.1. G e n e r a 1
The Pacific Gas and Electric Company (PG and E) supplies about
9 million inhabitants of Northern and Central California with gas
and electricity. Since the oil embargo in 1973 PG and E has sought
to increase the efficiency of use of fossil fuels and electricity
and to promote energy conservation in order to reduce the requirements
for purchasing foreign oil and extend the lifetime of natural gas
reserves.
Since 1974 PG and E has also explored the contributions of
alternative resources like coal, solar energy, wind, thermal ocean
streams and biomass. The biomass resources will be treated here more
in detail.
The biomass resources include agricultural field crop residues,
fruit and nut tree prunings, animal manures, forest and lumber mill
residues and municipal solid waste. The total quantity of these
biomass resources in the PG and E's service territory is about 30
million dry tons per year.
PG and E undertook a series of feasibility studies on biomass
resources, e.g. municipal solid waste (anaerobic digestion and
pyrolysis under controlled conditions, natural decomposition in
landfills), agriculture and forest residues and the use of excess
sewage digestor gas. PG and E is now involved in many projects using
biomass as an energy source for gas and electricity production.
10.2. R e c o v e r y o f b i o g a s a t t h e M o u n t a i n
V i e w L a n d f i l l
One of PG and E's projects is the Mountain View Landfill Gas
Recovery Project. The Mountain View Landfill is a large landfill
where about 500,000 tons of refuse are coming in each year. It is
a well managed landfill with compacted clay liners at the bottom and
on top of the landfill. A large part of the completed section is now
used as a golf course.
43
After a first feasibility study a demonstration project was
started at Mountain View. The construction of the gas recovery system
was completed in May 1978. Landfill gas is extracted here now from
30 acres with 33 wells. The extraction system is completely under
ground. There are no special constructions to prevent damage from
settlements. The vertical wells are attached to the horizontal
pipelines by flexible joints. Every year a piece of the vertical well
is cut off and a new joint is made with the horizontal pipes. Near
each well there is a small observation hole where the horizontal
pipe is connected to the well and where the flow velocity of the
gas can be measured and controlled.
The gas is compressed to 150 psig in two stages. In a gas
treatment plant water vapor, carbon dioxide and other impurities
(e.g. H„S) are adsorbed on alumina gel, activated carbon and molecular
sieves. Treatment is done sequentially in three towers, with one
tower on-stream while the other two are being regenerated by back-
flushing. After removal of the impurities the gas, which is of
pipeline quality now, is compressed to 400 psig for injection into
the transmission and distribution system of a gas utility for
delivery to customers.
The costs of investment for the treatment plant, wells and
collection system amounted to $ 840,000 ($ 1978) at a design ft *}
capacity of 1 x 10 scf per day (= 28,373 standard m per day).
Continuous operation is routinely achieved at 50 to 70% of the 3 design capacity, i.e. at 600-800 m raw biogas per hour. The volume
of gas produced in 1980, i.e. gas at pipeline quality, amounted to
about 2 x 10 m of gas in roughly 6000 operating hours (average 345 3
m per hour). The methane content of this treated gas ranges from
70 to 80% CH.. 4
The average composition of the gas extracted is: 44% CH,, 34% C0„,
21% N« and 1% 0„. It was found that continuous extraction resulted
in air being drawn into the landfill in spite of a 2 feet of compacted
clay cover. Because most of the oxygen was consumed by microorganisms
in the landfill, this resulted in an increase in nitrogen levels from
less than 1% (the level in the biogas produced) to 20-30% depending
on the extraction rate.
44
Problems encountered were failures in the adsorbers with respect
to moisture adsorption and separation of carbon dioxide from the
raw gas and introduction of air into the landfill and consequently
high nitrogen levels in the gas at higher extraction levels.
Because of practical problems with vertical extraction,
especially when the landfill is still in operation, an experiment
was started with horizontal extraction. The horizontal wells were
made from the outerside of the fill by horizontal drilling over
distances of 200-300 feet. The first results indicate that this
horizontal system is functioning quite well.
Another interesting project has been set up here last year
(June 1981). Six cells (10x10x13 meter) were filled with refuse
in different conditions. The cells are covered with a plastic
cover and underlined with compacted clay. In this study the effect
of moisture content, lime addition and leachate recycling on the
gas production is tested. The first results indicate that especially
lime addition (added as CaC0„-powder) has a beneficial effect on
gas production. Moreover the effectiveness of various extraction
systems and different covers (clay or plastic) will be studied.
10.3. L i t e r a t u r e
ANONYMUS, 1979. Gas Recovery and Utilization from a municipal waste
disposal site (final report). Conestoga-Rovers & Ass.,
Waterloo, Ontario
BARON, J.L., et al., 1981. Landfill methane utilization technology
workbook. CPE-8101, US Dept. of Energy
BLANCHET, M.J., 1981. Recovery and utilization of biogas at the
Mountain View Landfill. PG and E, San Francisco, CA
, B.M. JENKINS, J.G. MEYER, P. MACIEL, and R.F. GOLDSTEIN,
1980. Pacific Gas and Electricity Company: Biomass energy
activities. PG and E, San Francisco, CA
BRAY, P., B. JENKINS and M.J. BLANCHET, 1981. Mountain View Landfill
Gas Recovery Project. (Technical Report). PG and E & City
of Mountain View, EPA Grant No. S-803390
45
BROWN and CALDWELL, 1980. Landfill gas recovery, processing and
utilization in California. Brown and Caldwell, prepared
for State Solid Waste Management Board, Sacramento, CA
BUIVID, M.G., 1980. Laboratory Simulation of fuel gas production
enhancement from municipal solid waste landfills. PG and E,
San Francisco, CA
and D.L. WISE, 1980. Laboratory simulation of fuel gas
production enhancement from municipal solid waste landfills.
Report No. 2035 R2, Dynatech R/D Company, Cambridge,
Massachuetts
CLANCY, D.P., M.J. BLANCHET and R.E. HODGE, 1980. Probabilistic
model for sanitary landfill gas production. PG and E,
San Francisco, CA
FERGUSON, F.A., P.L. MORSE and K.A. MILLER, 19xx. Refuse as a fuel
for utilities. Prepared for PG and E by: Stanford Res. Inst.,
Menlo Park, CA
FLYNN, N.W., M. GUTTMAN, J. HAHN and J.R. PAYNE, 1981. Trace chemical
characterization of pollutants occurring in the production
of landfill gas from the Shoreline Regional Park Sanitary
Landfill, Mountain View, California. Science Applications,
Inc., prepared for PG and E, San Francisco, CA
HERSFIELD, B.C. and B.M. JENKINS, 1977. Agricultural residues as
an alternative source of energy for the Pacific Gas and
Electric Company. Dept. Agric. Eng., Univ. California,
Davis, CA
PACEY, J. et al., 1982. Controlled Landfill Project (first annual
report): Construction and Operation. Report on Mountain
View Landfill Project prepared for PG and E, EMCON Ass.,
San Jose, CA
PACIFIC GAS AND ELECTRIC COMPANY, 1981. Bioconversion feasibility
study cattle manure to methane. Report PG and E, September
1981, San Francisco,CA
PG and E, 1981. Development of the utilization of combustible gas
produced in existing sanitary landfills: Effects of corrosion
at the Mountain View Landfill Gas Recovery Plant. PG and E,
San Francisco, CA
46
PROCEEDINGS of a working symposium on 'Methane from Landfills: Hazards
and opportunities'. Symp., March 21-23, 1979, Denver, COLO
WILSON LANGTON, E., M.G. BUIVID and D.L. WISE, 1980. Laboratory
experiments on in situ fermentation of combined agricultural
residues. Report No. 2031R2, Dynatech R/D Company, Cambridge,
Massachuetts
47
APPENDIX 1
ITINERARY May 10 - June 12, 1982
May 16
May 22
May 10 - 13 Conference on Resource Recovery from Municipal,
Hazardous and Coal Solid Wastes, Miami Beach,
Florida
- 21 Groundwater Modeling Course, Holcomb Institute,
Butler University, Indianapolis, Indiana
- 25 Solid and Hazardous Waste Research Division,
US Environmental Protection Agency, Cincinnatti,
Ohio.
Meeting with Dr. Ron Hill*, Dr. Norbert Schomaker
and staff; excursion to CECOS-landfill
Symposium on Aquifer Restoration and Ground Water
Monitoring, Columbus, Ohio
June 2 Georgia Institute of Technology, Atlanta, Georgia
Meeting with Prof. Dr. Frederick Pohland, Prof. Dr.
Edward Chian and staff
Department of Soil and Crop Sciences, Texas A & M
University, College Station, Texas.
Meeting with Jan Green and staff members of the
Department
June 8 US Water Conservation Laboratory, Phoenix, Arizona
Meeting with Dr. Herman Bouwer and staff
June 9 Matrecon, Inc., Oakland, California
Meeting with Dr. Henry Haxo and staff
June 10 Pacific Gas and Electric Company, San Francisco,
California
Meeting with Dr. Max Blanchet; excursion to
Mountain View Landfill
June 12 Return to the Netherlands.
May 26 - 28
May 31
June 3 - 7
*The author is greatly indebted to Dr. Ron Hill and coworkers, who composed the complete itinerary and made the arrangements with the institutes visited, and who even took care of the hotel reservations.
48