CA1079650A - Coal-base landfill, leachate treatment - Google Patents

Abstract

AN ABSTRACT OF THE DISCLOSURE
The prevent invention concerns the use of selected and improved adsorbent coal materials to provide a high degree of treatment for landfill leachates, in a simple effective and economical manner the process involves a unique way of collecting leachates from either a newer controlled type of landfill operation or the conversion of an uncontrolled type, and again the process may be used to upgrade older covered fills of refuse to correct potential leachate problems therefrom.
According to the invention the landfill leachates are collected, removed and treated to an acceptable standard suitable for discharge to surface waters or re-cycling to the landfill operation.

Description

This invention relates to landfill operations, and in particular to a method of recovering and treating the leachate therefrom before discharge.

Nearly 90 per cent of the solid waste generated in Canada i8 disposed of in a landfill of one 80rt or another. The ban on open burning at these sites has led to the contamination of underground and surface waters by waters draining from these fills. Referred to as leachate, this contaminated water i8 presumed to result from the percolation of precipitation through the land-fill and or by the direct interception of the water table with the buried refuse.

When municipalities dump their garbage they often overlook the hydrogeology of an area, yet they may have known for years that when waste is disposed of beneath the soil, dissolved solids, bacteria and viruses can enter and travel in the groundwater.

Part of the problem has been that the old-style garb-age dump never apPeared to cause a health problem. It was also kept fairly acceptable by open burning, and was usually in an out of the way location. Thus the public had little reason to complain.

Groundwater is the basic water source for many millions of Canadians. L2achate from solid-waste fills is gaining recognition as a mounting threat to groundwater purity.
It i8 estimated that, leachate, mainly consisting of rain and the contamination it soaks up as it percolates through the refuse fill, contains about as much BOD as the Nation's entire discharge of untreated raw sewage.

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" 10796~0

- 2 -Soil and water are said to be polluted when the health of humans or animals i~ impaired by consuming the food grown on the 80il or by drinking the water that had contact with the 80il.

When wastes are applied to a 80il~ our expertise in Protecting groundwater from landfill lcachate must take into consideration the development of by-products or derivatives from the leachate that may be toxic or that may accumulate and threaten our food chain.

A wa~te applied to a soil should only be considered safely disposed of wh~n-a) The BOD has been lowered to acceptable limitss in the order of 4ppm for liquid ~ffluent~

b) Water flowing over or through the 80il meets the required standards as to chemical pur$ty, ta~te, colour and odour~

c) Soil and water have not been polluted and it ~ ha~ bean demonstrated that the waste, or its ; by-products, are not building up to toxic levels in 80il or water.

Apparently, few basic studie~ related to gaining an und~rstanding of the bafiic character~stics o~ leachates ; have b~en reported. Some fitudies done on the Pacific Coast, ~ndica~e that "leachate quantity and character i8 dependent upon th~ amount of moisture traveling through the systen as well as th~ time and placement of the material in the landfill.
, An analysis of leachate from two landfill sites have been carried out in cooperation with the inventor, the results of these measurements are shown in the following Tables 1 and 2.

Table 1-Range of Concentration - Sanitary_Landfill L achates ~Concentration - mg/litre Ion Range Iron 200 - 1700 10 %inc 1 - 135 Phosphate 5 - 130 Sulfate 25 - 500 Chloride 100 - 2400 Sodium 100 - 3800 Nitrogen 20 - 500 Hardness (as CaC03~ 200 - 5250 Chemical Oxygen Demand100 - 51000 Total Residue 1000 - 45000 Nickel .l - 0.8 20 Copper 0.10 - 9.0 : pH 4.00 - 8.5 ~ n analysis o~ the inorganic ions present in leachate emanating from the two converted landfill disposal sites is given below. m e-first site is located on basaltic bedrock thereby allowing little penetration of run-off - water into the underground water table. m e results of analysis of a selected number of inorganic ions in the site leachate is as follows.

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' 10796~iiQ

Compound Parts per Million pH
Ammonia 5S.5 7.8 to 8.0 Copper 0-05 :~
Chromium 0.02 -Chloride 400 Calcium 132 Fluoride 0.42 Iron 1.72 Manganese 0.10 10 Nitrate 14 Phosphate 0.65 S~lica 22.5 Sulfate 10.0 Zinc 0.05 A~ the second site, the upper and lower limit~ of the concentration of various inorganic ions were analysed during the ~u~mer months. The results are given below.

Compound Part~ per Million pH
-- .
Iron 2.0 to 5.8 6.6 to 7.4 Pho~phate (ortho) 0-04 to 0.68 20 Calcium 160 to 240 MagnQsium 80 to 150 Nitrogen ( nitrate & Nitrite) 12 to 24 Sulfate 50 to 225 ;.
Silica 36 to 60 Chloride 75 to 80 ~oth sulfate and iron occur in concentrations exceed-ing the limits set by Public Health Authoritie~.

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- 107~650 Con~iderable data applicable to the decontamination o~ leachate is available since the treatment of contam-inated water represents a problem of great concern ~o a major portion of industrial and public enterprises and the problem has been studied extensively. Conventional primary and secondary treatment processe~ may not provide the required degree of cons$~tency, nor do they provide sufficient treatment for the protection of natural waters from a variety of organic and inorganic pollutants, mat- :
erial8 which contribute to the chemical oxygen demand, '~i.o-`'chen~cal oxygen demand, colour, tasteJ odouri as well as certain pathogens.

Research and development on advanced physioch~mical processes for waste water treatment has been centered primarily on tertiary treatment processes for waste already subjected to conventional secondary biological treatment. m e additiono~ tertiary-level physiochemical processes to conv~ntional secondary treatment incurs significant addional expenses often without providing a completely satisfac~ory result.

Clearly, a low cost, highly effective method of remov-ing conta~inants from water would represent a signi~i~ant contribution to the solution o~ one of mankind's most pressing environmental probl2ms.

A variety of approaches to waste water treatment have been ProPosed and exPerimented with in recent years-1~796SO

Several important developments have given a naw i~p~tus to the u~e of activated carbon for larqe scale water treat-ment application. Activated carbon filtration constitutes a step in the tertiary treatment at the South Tahoe, U.S., sewage treatment facility. Other investigations of proc-essing raw sewage by a two step process of clarification and carbon adsorption have dramatically demonstrated the potential of the technique. These investigations have dem-on~trated the economic and practical advantage of using carbon in the water treatment Process- The cost of activ-ated carbon i8~ however, a large factor in ~he economic viability of adsorption techniques~ regeneration of the carbon when sPent~ i8 an important factor in most presently commercial schemes-At Present, activated carbon is one of the most prom-ising solid adsorbents owing to its commercial availab-ility, high adsorptive capaci~y and affinity for a broad spectrum of chemical compounds, Organic compounds that can be removed from aqueous solution by active carbon in-- 20 clude phenols, cresols, alkylbenzen-sulfonates, nitroch-loroben~enes, chlorinated paraffins, butadiene as well as certain synthetic dyes, insecticides and fungicides.
.
As an additional benefit, further remoYal of contam-inants has be~n observed as a result of biological activity in carbon filter bed~. It is thought that the highly adsor-bent carbon surface actually enhances the growth of biolog-ical organisms because of its large surface area and its capacity to hold nutrient~.

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1(~79650 Within recent years, a large naturally occurring deposit of carbon possessing properties similar to activated carbon ha~ been located- A~ a result of thousands of chemical tests and practical application in the field the results seem to indicate that the natural active carbon may be as effective as the synthetically produced activated carbon in waste water purification of both organic and inorganic contaminants. If so, because the carbon may be produced at a fraction of the cost of high grade a~tivated carbon, the dramatic cost reduction will allow many new uses in water purification needs, previou~ly found economically unfeasible.

Unlike s y nthetic activated carbons the te~t results clearly demonstrate a significant adsorption cap3city o~
the natural form of active carbon for most catiOnS and ~everal anions- The tests also suggest adsorption capacities comparable with the best activated carbons in the case of phenols.

The following table shows the value of the natural carbons in the treatment of contaminants.

Inorganic Ion Adsorption One of the unusual properties of the natural active carbon is its apparent ability to adsorb a variety of inorganic ions. The procedure ~ollowed in testing the ad-sorption properties of the carbon involves (1) Preparation of standard solution; (2) sieving of the carbon to a l/4"
to L/l6" PartiCle size~ t3) three different washing procedures involving (a) a distilled 1{~796~50 water wash, (b) a HCl acid wash, (c) a NaOH base wash, (d) a base then acid wa~h.

(ppm~ Neutral Acid Base Base then Contact Initial Wash Wash Wash Acid time Hr3 concentration æ~nc 30 0~6 1.0 Zinc 30 0.3 3.0 Barium300 22 1.0 Barium300 5 2.0 Copper 10 0.08 4.5 6.5 1.1 Iron 10 .51 3.7 1.1 1.7 1.5 Man ganese1146.30 81.0 6.3 43.0 1.0 Chromate105.00 .2 .1 .1 1.0 Chromate10.025 18.0 Sulfate200250.00120.0 150.0 1.0 Phosphate 50 37.50 33.8 13.1 1.0 Pho~phate 50 6.0 11.1 3.0 Chloride 30 32.50 Nitrate200249.00115.0 90.0 5.0 Nitrite109105.00 1.5 Cyanide7010.00 1.0 Cyan$de70 8.00 2.0 Cyan~de70 1~10 20.0 ~mmonium 30 5.0 1.0 Am~onium 30 2.8 4.0 796~{) ~he results shown heretofore, clearly indicate a strong adsorption tendency toward~ most cations and the anions, CN , CrO4 and to some extent P04 . Both nitrate and phosphate have been significantly removed by the carbon when a biol-ogical community is developed. The acid and base treated carbons appear to have enhanced ability to adsorb nitrates, phosphates and sulfates. It should be pointed out that longer contact times will probably lead to increas~d ad~orp-tion since equalibrium appears to r~quire several hours (e.g., ~ee chromate re~ults) in some ca~es.

Organic Ad~orption The following studies have been carr$ed out U8 ing phenol and nitrobenzene. Ten grams of neutral washed carbon was treated with ten grams of pure nitrob~nzene and ten grams of 90X aqueous solution of phenol for one hour. By weighing the carbon before and after exposure to the organic the r ~ollowing results were obtained~
g of organic adsorbed/g of carbon Phenol 0.19 Nitrobenzene 0.16 , Thes~ re~ults compare favorably with the results of a study in which phenol and nitrobenzene were adsorbed on a large area commercial activated carbon. This activated carbon, which possessed a surface area of 1200 m2/g, adsor-bed O.094 grams of phenol/gram of carbon and O.22 grams of nitrobenzene/gram of carbon.

These result~ ~how that the natural carbon ad30rption of the e two organics i8 equal to that of a high grade synthetic activated carbon.

-" 1079650 The following tests were done to determine the treat-ment effectiveness of the natural carbon in which a biological community has built up~ and which had been in use in the treatment of meat-packing hou~e wastes for a period of 26 months without regeneration or replacement.

Contaminant Removals. Before Treatment. After Treatment.
Phosphate (ortho) 65.0 ppm .08 ppm Phosphate (total) 85.0 ppm 2.1 ppm Biological Oxygen Demand 750 ppm 10 ppm ;;.
This invention relates in part to Canadian Patent App-lication No. 228,069 Filed May 29, 1975.

I have outlined heretofore the disadvantages associated with the collection and treatment of ~olid wastes and the leachates issuing therefrom, in b oth controlled and un-controlled landfill operations, and have outlined herein by laboritory tests the benefits to be gained from the use of adRorbent natural carbons for such landfill leachate treatment.

It is an object of the invention to provide a new and improved process for the collection and treatment of land-f ill leachates issuing from both controlled and uncont-rolled landfill operations, that will effectively remove a variety of contaminants from the leachate.

An important objective is to remove the greater per -centage of BOD and COD from the leachates-Another object is to remove from leachates the heavymetals therein.

A prime objective of the invention is to provide an 1~79650 adsorptive curtain wall of carbon to surround old landfill operations, so placed as to intercept and treat the horiz-ontal flow of leachate originating from the refuse therein.

An additional object of the invention is to provide a process for treating landfill leachates which will remove offensive odours therefrom.

A still further object of the invention is to provide a process for removing harmful bacteria, pathogens and viruses from the landfill leachates to prev~nt them from passing into the groundwaters.

Still other objects and advantages will become appar-ent hereinafter.

I have found that the aforementioned di3advantages may be overcome and the objectives achieved by providing treat-ment for the landfill leachates as is ~hown and described in the following numbered drawings and description.
,, In accordance with the present invention, therefore, the landfill leachates are treated within a prepared land-fill site comprising a drained impervious base, which is overlaid with an impervious liner, covered by layers of adsorbent carbon. A plurality of interconnected perforated flexible pipes are laid within the carbon, and serve to gather and conduct the leachate to the collecting sump-wells, which extend vertically to the surface of the land-fill. The refuse is placed upon the carbon, and in use the leachate passes through the refuse and is conducted through the perforated pipe to the collecting well --` 1079650 and then pumped to a plurality of separation bed~, bio-ogical treatment beds, and tertiary treatment beds for treatment. ~-Referring now to Drawing 1 of Sheet 1, indicated at 10 i8 surface water into which landfill leachates from a typical uncontrolled landfill operation may be seeping.
Indicated a~ 11 i8 a vertical curtain wall designed to stop the horizontal flow of groundwater carrying leach-ates therein indicated at 13. The curtain wall 11 comp-riQing two vertical wall sections, an inner wall indic-ated at 8 fonmed ~y pervious polyvinal ~hloride (PVC) heavy sheeting on the landfill side, and an outer wall formed by impervious polyvynal chloride (PVC) heavy sheeting indicated at 9. Indicated at 7 i8 shown an inner core of granular selected adsorbent coal. within the inner core section 7 leachate recovery wells indicated at 12 are recessed into the base thereof. In practice the leach-ate-groundwater indicated at 13 issues from the landfill areas indicated at 14 and passes into the curtain wall indicated at 11 through the pervious wall indicated at 8.
The leachate is Prevented from passing into the surface water indicated at 10 by the impervious outer wall of the curtain wall indicated at 9, and i8 collected therein for removal by means of pumping the leachate from the wells 12.

Referring now to Drawing 2 of Sheet 1, indicat~d at 16 is a well cros~ section. Indicated at 19 is a landfill refuse, within which a well 12 may be sit2d outside the curta$n wall 11. The refuse leachate 22 passes through the r~gid pervious wall 21 to become the leachate 23.
At 24 is the sump section of the well and indic-. ~

ated at 20 i8 bedrock or base of the landfill area within the well. The leachate 23 is withdrawn from the well 16 through the pipe indicated at 15., at the bottom end of the pipe 15 is a ~tandard waterwell screen indic-ated at 18. ~he withdrawal pipe 15 i~ made of stiff black plastic PVC indicated at 17.

Referring now to Drawing 3 of Sheet 2, indicated at 25 i8 a controlled type of landfill operation. Indicated at 26 is a solid ba~e of undisturbed earth, into ~hich a groundwater collection trap i8 recessed, the trap i8 indicated at 30,The walls of the trap 30 are made of pervious material 31. within the trap is laid perforated groundwater collection pipes which are indicated at 27.
Enclosed within the trap and forming a surround for the perforated pipe 27 are selec~ed adsorbent natural coal material~ indicated at 29. On ei~her side of the trap 30 is placed optionally a layer of pervious sand or naturally adsorbent active carbon 29 to the top of the trap 30.
Overlying the solid base 26, trap 30 and level fill ind-icated at 28 comprising either pervious sand or naturalcarbon 29 i8 a thick impervious sheet of polyvinal chloride ~PVC) indicated at 31. A ~ixx inch base cover of s~lected 29 naturally active adsorbent coal i~ laid over the entire -~
landfill site, into which leachate traps 32 are recessed at intervals across the refuse di6posal area 25. Perforated collection pipes indicated at 33 are la~d within the leachate traps 32 with a surround of 3elec ted naturally active adsorbent coal 29. A ~olid layer of clayey soil is placed over the entire working area of -`\ 1079650 the landfill as indicated at 34. At suitable spaced int-ervals perpendicular well piping indicated at 35 is joined together with the leachate collection pipes 33 and sump 22 from which the leachate and sludge may be pumped. Indicated at 36 is the refuse of the landfill operation.

Referring now to Drawing 4 of Sheet 2, indicated at 37 is an uncontrolled landfill operation, the greater major-ity of this type of refuse disposal have limited if any controls governing their operations. If site plans are available for this type of landfill it i8 best to sink leachate ræovery wells at low points indicated on the plan. Since water does not always flo~ downhill because of certain qeological and impermeable strata, it will likely be found that almost any well drilled into an old garbage dump will draw water to it, even up hill. Indic-ated at 38 are wells for the removal of leachates for treatment.

Referring now to Drawing 5 of Sheet 3, indicated at 40 is a landfill area. Indicated at 41 i8 the leachate coll-ection and recovery well. The leachate i8 pumped from thewell by pump indicated at 42 and is Passed into the line indicated at 43 through which iB received the leachate to be treated. If the leachate is carrying large amount~
of ea~ily settlQd solids, it i8 preferably passed through a settling tank, indicated at 44, to permit such solids to settle out. Optionally the leachate effluent is treated with a polyelectrolyte prior to the passage of the leachate into a ~iblogical tr~atment bed comprising a smaller sand section indicated at 45 10~9650 and a larger filter section indicated at 46. The first treatment bed is shown as a dual media bed as i8 indic-ated at 47, having a first smaller section of relatively fine filter material and a larger filter section of relat-ively coarse filter media. The difference in the particle sizin~s of the media may vary according to the nature of the leachates and the type and amount of pollutants therein.
Preferably the particle~ in the longer section 46 are of materials of lower density than that of the smaller section 45 PartiCleS- m e difference in the density helps to main-tain separation between the sections particularly during backwashing operations. Whilethe desirable size range of the filter media may vary as aforemention~d, the particles of the coarse section 46 should be substantially larger in diameter than those particles of the finer media in section 45. The coarse particles may range, for example, from about 1/8 inch to about 3/4 inch. The coarse section ~6 should preferably have a depth of not more than about 12 inches and the level of the effluent in the treatment bed should not be above about 8 inches as measured from the bottom of the bed to provide odour control therein.

The section 45 is preferably formed of a relatively dense material such as silica sand. The particle ~ize should be substantially smaller than the particle size of the coarse media in section 46. The sand may range in size from about 0.04 to Q.01 inch. The section 45 should have a depth of at least 6 inches and preferably a depth of between about 6 to 12 inches.

1~796~i0 -16- ... -;
After a period of about a month or when a backpressure develops which tends to restrict the free flow of the eff-lent through the treatment beds, a cleaning procedure in-volving the backwashing of the beds to remove normal degrad-ation materials and windblown debris therefrom is carried out. This is done by PaSsing a reverse flow of water through the beds indicated at 47. Clean water from any available source iB pumped into and through the treatment beds in a reverse flow pattern to dislodge and remove the effluent degradation materials and windblown debris from the adsor-bent coal treatment media in the beds, as an effluent sludge, and then the backwash water and effluent sludge is - discharged from the treatment beds indicated at 47 and carried through the carrying line indicated at 48 and ret-urned to the settling tank indicated at 44 for settling.
The effl~ent from settling tank indicated at 44 is then passed into the biological treatment bed 47 in the dir-ection through the smaller sand filter..section indicated at 45,to remove any solids therefrom and then through the longer filter section containing celected adsorbent natural coal carbon in coarse particle sizings therein. A biolog-ical community is developed naturally within the bed and is enhanced by returning part of the bacteria-laden outflo~
from-the bed to the inflow of the longer bed section 46 for the purpose of inoculation. The removal of BOD and ~OD producing ingredients is carried out in the first beds indicated at 47 without the production of any odours there-from by maintaining the effluent level within the beds below that of the top of the carbon indicated at 49 there-in. As is indicated in a following table the bacterial content of total coliform and faecal coliform are removed by the selected natural carbon -' 1079~;S0 in contact therewith. Provision is made for the removal of phosphate-containin~ substances in the effluents by providing in the plurality of treatment bed~ a ~ed or a section of a bed which will contain a selected natural adsorbent carbon having an affinity for phosphates in the effluent to remove it therefrom. The effluent flow is indicated at 53 and the backwash flow is indicated at 54. The effluent from bed indicated at 47 is passed the second biolo~ical treatment bed 47 or a plurality 10 of such beds, and is then passed into a plurality of treatment beds by means of carrier line indicated at 55, wherein tertiary treatment i~ provided the leachate eff-luents to remove any remaining pollutants therefrom. The tertiary treatment beds indicated at 48 contain a sel-ected natural adsorbent carbon having an affinity for tertiary type pollutants which may remain in the leach-ate effluent~, to remove them therefrom. The treated leachate effluents are then discharged from the treatment bed of the treatment system by means of discharge pipe 20 indicated at 56 for di~charge to surface waters indic-ated at 52 or to be re-cycled to the landfill operation indicated at 51. The aforementioned water discharged from the final treatment bed will be of a standard of quality suitable and acceptable to pollution control agencies for such discharges. The backwashing of the system is carried out be means of the pump indicated at 50 and the water carriage lines indicated at 55.

-- iO796~;0 An idea of the treatment effectiveness of a selected naturally adsorbent carbon in the removal of harmful bacteria from wastewater after such treatment may be seen from the following report.

Excerpts from a letter (on file) concerning tests made by the B.C. Pollution Control Branch, as reported to the -Chief Health Inspector, Capitol Regional District, Vict-oria, B.C., Dated January 22, 1975.

"attached are the results of tests on the coal system of sewage treatment"..-We ran the tests for our own information as to how the material worked on domestic sewage, however, we thought you might be interested in the results."

"rel Treatment of Domestic Sewage with Pulverized Coal.
~ high degree of reduction has been achieved for some parameters including total and faecal coliform levels.
"... m e degree of treatment provided by this sy~tem is better than level "A" of the "Minimum Requirements for disposal of Municipal and Domestic wastewaters to surf-ace waters".

"...July 3, 1974.

T. Coliform Infl. 9.2xlO Eff. 9.2x104 Red. 99%
F. Coliform " 4.9x105 7 x103 " 99%

In summary the process of the invention involvesthe steps of~

1. Providing a suitable way of collecting and rem-oving leachates from both controlled and uncont-rolled landfill operations.

--19-- :
2. Collecting leachates originating within a controlled landfill operation by conducting the leachate by means o~ perforated piping laid within adsorbent coarsely sized coal, to rece~sed filter traps cont-aining therein the coarsely sized adsorbent coal.

3~ Providing a means of settling out solids from the leachates by forming well sections extending to the surface of the refuse from the recessed filter trap where the well has a lower ~ludge sump and an upper effluent section.

4. Collecting the leachate within the well which orig-inates from the perforated piping, the filter traps and through the pervious wall of the wells-

5. Remo~ing the collected leachate from the wells in both controlled and uncontrolled landfill operations by means of pumps and conducting it to a settling tank.

6. Removing any re~aining e~fluent solids in the leachate by the addition to the leachate of an adsorbent powd-ered-coal flocculatin~ a~ent, with agitation, and then optionally adding as required a polyelectrolyte settling agent.

7. When found necessary removing the settled sludge from the well sumps and from the settling tank and inter-mixing the cludge with a further addition of powdered adsorbent coal and recyc~ing the coal-sludge mixture back to the landfill operation.

- ~ 10796~0

8. Passing the effluent from the settling tank into a dual media filter comprising firstly a smaller sand section wherein the sand particles have a sizing ranging in size from about 0.04 to 0.01 and is placed within the filter to a depth of between 6 inches and 12 inches.

9. The effluent is then passed into a longer filter section containing therein coar~e sizings of sel-ected adsorbent coal having a range of sizings ranging from about 1/8 inch to about 3/4 inch, wherein the leachate organic matter is oxidized by biological activity, and where the biological activity may be enhanced by re-inoculating the biological community in the treatment bed by re-cycling the outgoing effluent from the b~d back to the first section of the coal filter media.

10. Maintaining odour control within the treatment beds by keeping the effluent level in the bed below that of the top of the coal treatment media.

20 11. Selectively removing the total coliform, faecal coliform and pathogenic bacteria from the land-fill leachate by treatment with the selected adsor-bent coal materials.

12. Removing BOD and COD causin~ pollutants from the landfill leachates by treatment with selected adsorbent coal material~.

~079650 13. Providing tertiary treatment as a final polish-ing stage of leachate treatment to remove any remaining pollutants therein.

14. Discharging after treatment an effluent having a water quality of acceptable standard suitable for discharge to surface waters or for re-cycling back to the landfill operation.

15. Providing a plurality of biological and tertiary ~;
treatment beds using a plurality of differing selected adsorbent coal materials, for use in removing pollutants from landfill leachatesO

16. Determining the pollutant content and concentra~-ion thereof by analysing the landfill leachates.

17. Selecting the most suitable adæorbent coals for use in the treatment of landfill leachates chosen from the group of coals consisting of most ranks of coal and coal ~astes excepting anthracite coal.
In determining the coal suitable for use in the leachate treatment procedure thin sections of coal are examined by microphotograph study to determine the physical characteristics, the cont-ent of surface chemicals and crystals thereon, and the adsorptivity of the coal to remove the polluting leachate contaminants as found by aforementioned analysis.

18. Crushing, pulverizing and sizing the selected ; coals to provide treatment sizings which may range from 3 inches down through -200 screen mesh size.

19 Improving the ad~orptive affinity of the selected `~
coal ~y a process which involves artificial weath-ering which comprises boiling the coal particles in water for about 5 to 30 minutes, or subjecting the coal particles to a steam bath, or washing the coal particles with solvent solutions chosen from hot or cold water, an HCl acid wash. a NaOh base wash, or a base then acid wash. The optionally drying the coal particles at a temperature of from about 100 C to 200C for a sufficient period of time to effect the removal of the moisture and or easily volatilized substances or gases therein, or from about 1 to 10 hours.

20. Providing selec~ed adsorbent coal in size ranges suitable for use for the purpose intended of the invention wherein a sizing of from about 3/4 inch up to about 3 inches may be used in the filter traps, as a cover for the landfill base, and for a coal surround for the perforated collection pipes within the con~rolled landfill operation. And wherein a powdered sizing of the adsorbent coal is used in the treatment of the leachate effluent passing into the ~ettling tank for use as a flocc-ulating agent, this Powdered sizing includes all those pulverized ad~orbent coal materials in which the maximum size is that passing a standard 200 mesh size screen. ~nd wherein the sizing of the adsorbent gra~ular coal materials used in the biol-ogical treatment beds and the tertiary treatment beds as well as the curtain wall is preferably of from about 1~8 inch to 3/4 inch or selected sizings within that range.

1(3796So 21. A further additional step i9 the conver~ion of an uncontrolled landfill operation to a controlled landfill operation wherein a vertical impervious `
curtain wall is provided to surround or cut-off the horizontal flow of leachate issuing from the landfill operation, within which a second vertical wall of pervious construction i5 placed, and wherein the pervious vertical wall and the impervious vertical walls are separated one from the other by an inner core comprising adsorbent granular coal in predet-ermined sizings- Leachate recovery wells are rece~sed into the base of the landfill and the aforesaid inner core section separating the two wall sections.
The wells consisting of a lower sump section for the collection of settl@able solids from the leachate, and an upper section for the collection of the set-tling leachate effluent, The wells, extending ~ertic-ally from the recesced sump area through the iand-fill refu~e and adsorbent coal treatment media to ~ !
~he landfill sur~ace, are formed from rigid pervious non-degradable material. m e leachate from the solid refuse percolates through the inner pervious vert-ical wall and thence through the inner core section of adsorbent granular coal and is then passed through the pervious rigid wall of the c~llection well and, when the solids are settled therefrom the settled effluent i~ then pumped from the well to a settling tank and is then treated by the aforementioned leach-ate process outlined heretfore.
22. Backwashing the biological treatment beds and the tert-iary treatment beds when a backpressure is found build-ing up within the beds which restricts the free flow of the leachate effluent therethrough and conducting the wash-debri~ back into the settling tank.

22. Backwashing the biological treatment ~eds and the tertiary treat~ent beds when a backpre~ure is found building up within the beds which re~tricts the free flow of the leachate effluent therethrough and cond-ucting the wash-debris ~rom the beds back into the settling tank.

Having illustrated and described a preferred ~mbodiment of the invention, it hould be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true 3pirit and scope of the appended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for treating landfill leachate in which the landfill installation has an impervious base overlaid with leachate collection pipes leading to sump wells from which leachate is extracted to biological and tertiary, leachate-treatment beds comprising pulver-izing, screening, artificial weathering, and rescreening sorptive granular coal to a first size between 1/8 and 3/4 inch, a second size between 3/4 inch and 3 inches, and a third size of less than 200 mesh, covering said base and sump wells with said second size coal, with-drawing leachate from said sump wells, adding said third size coal to the pumped leachate, and filtering said leachate through biological and tertiary treatment beds composed of said first size coal.