CA1079876A - Coal-base landfill leachate treatment - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present 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 there-from. 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

lV79876 This invention relates to landfill operations, and in particular to a method of recovering and treating the leachate there~rom be~ore discharge.

Nearly 90 per cent of the solid waste generated in Canada is disposed of in a land~ill of one sort or ànother.
The ban on open burning at the~e site~ has led to the contamination of underground and surface waters by water~
draining from these fills. Referred to as leachate, this contaminated water ~s presumed to result from the perc-olat~on of precipitation through the landfill and or bythe dixect interception of the water table with the buried refuse.

When municipalities dump their garbage they often over-loo~ the hydrogeology of an area, yet they may have known for years that when waste i~ disposed o beneath the soil, dissolv~d sollds, bacteria and viruses can enter and travel in the groundwater.

Part of the problem has been that the old-~tyle garbage dump n~ver appeared to cause a haalth Problem. It was also Xept fairly acceptable by open burning, and was usually in an out of the way location. Thu~ the public had little r~ason to complain.

Groundwater i~ the basic water source for many million3 0~ Canadians- Leachate from solid waste fills i8 gaining recognition as a mounting threat to groundwater purity.
It i~ estimat~d that, leachate, mainly consisting of rain and the contamination it soaks up as it percola~es through the reus~ fill, contain~ about as much BOV as the nation's entire discharge of untreated raw sewage.

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107~876

-2-Soil and water are said to be polluted when the health of humans or animals i8 impaired by consumlng the food grown on the 80il or by drinking the water that had contact with the soil.

When wastes are applied to a ~oil, our expertise in protecting groundwater from landfill leachate must take into eonsideration the development of by-products or derivatives from the leaehate that may be toxic or that may accumulate and threaten our food chain.

A waste applied to a ~oil should only be considered safely disposed of when-a) The BOD has been lowered to aeceptable limits~
in the order of 4 ppm for liquid effluents~
., b) Water ~lowing over or through the 80il meets the r quired standards as to ehemical purity, taste, eolour and odour~
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c) Soil and water have not been polluted and it has been d~monstrated that the waste, or its by-products, are not building up to toxic levels in soil and water.

Apparently, few basic studies relat~d to gaining an understanding of th- basie eharaeteristics o~ leachates have been reported. Some studies done on the Pacifie Coast, indieate that ~leachate quantity and eharacter 18 dependent upon the amount o moisture traveling through the system a~ well as the time and placement of the material in the land~ill.

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An analysi~ of leachate from two landfill ~ites have be~n carried out in cooperation with th~ inventor, the re~ults of these measurement~ are shown in th- following Tables 1 and 2 T~ble 1 Range of Concentration - Sanltary Landfill Leachates Concentration - mg/litro Ion Range Iron 200 - 1700 ~inc 1 - 135 Phosphate 5 - 130 Sulf~to 25 - 500 Chloride 100 - 2400 Sodlum 100 - 3800 Nltrogen 20 - 500 Hardne s (as CaC03) 200 - 52S0 Ch _ lcal Oxyg-n Demand100 - 51,000 Total Rs idue 1000 - 45,000 Nickel 0 01 - 0 8 Copp-r 0 10 - 9.0 PH 4.00 - 8 5 An analysi~ o~ ths inorganic ions pr~ent in leachate emanaeing from the two converted land~ill dispo~al ~ites ~: i8 given below me first slte i~ located on basaltic : ~ :
bedroc~ thereby allowing littlo penetration of run-of~

wat-r lnto the underground water table. The results of analy~io of a selected number of inorganic ions in the lt-~leaehate i- as follows ~ ~ .

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~07~376 Compound Parts per Million pH :
~mmonia 55.5 7.8 to 8.0 Copper 0-05 Chromium O.oz Chloride 400 Calcium 132 Fluoride 0.42 Iron 1.72 Manganese 0.10 10 Nitrate 14 Phosphate 0.65 Silica 22.5 & lfate 10.0 Zinc 0.05 At the second site, the upper and lower limit~ of the concentration of variou~ inorganic ions were analysed during the su~mer months. The results are given below.

Compound Parts per Million PH
Iron 2.0 to 5.8 6.6 to 7.4 Phosphate (ortho) 0-04 to 0.68 Calclum 160 to 240 Magnesium 80 to 150 Nitrogen ~Nitrate ~ Nitrite) 12 to 24 Sulfate 50 to 225 - Silica 36 to 60 Chloride 75 to 80 Both ~ulfate and iron o~cur in concentrations exce~d-ing the limits sQt by Public Health Authoritie~

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- 1~)798'76 Con~iderable data aPPlicable to the decontamination of leachate i~ available ~ince the treatment of contam-inated w~ter r~presents a problem of great concern to a major portion of industrial and public ~nterPrise~ and the problem has been studied extensively Conventional prlmary and secondary treatm~nt processe6 may not provide the requir~d degree of cons~stency, nor do they provide sufficient treatment for the protection of natural waters from a v~riety of organic and inorganic pollutants~ mat-rials wh~ch contribute to the chemical OXygQn d~mand, the~io ~chemical oxygen demand, colour, tastQ~ odour~ ~8 well a~ certain pathogen-Re earch and d~velopmQnt on advanc d physioche~icalproc-~se- for waste water treatment has beon centered prlmarily on tertiary troatment proce~ses for wa~te al-r-ady sub~ect-d to conv-ntional econdary b~ologic~l treat-ment The addition of tertiary-level physiochemical proc-e-se- to conventional secondary treatm-nt incurs signif-icant addition~l exp~nses o~t-n without providing a comp-letely sati~factory r~ult Clearly, a low cost, highly offective method of r~mov-ing contaminant~ from water would repre~ent ~ significant contribution to th~ solution of one of mankind~'~ most pre~-ing environ~ental probl~ms ~ .
A variety of approaches to wast- water treatment have been propos~d and experimented with in rocent year~ ~

: ' Several important developments have given a new impetus to the use of activated carbon for large 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 inve~tigations of proc-essing raw sewage by a two step process of clarification and carbon adsorption have dramatically demonstrated the potential of the technique. These investigation~ have demonstrated the economic and practical advantage of using carbon in the water treatment process. The cost of act-ivated carbon is, however, a large factor in the economic viability of adsorption techniques~ regeneration of the carbon when spent, is an important factor in most presently commercial scheme~.

At present, activated carbon is one of the most prom-l~ing solid adsorbent~ owing to its commercial availab-ility, high adsorptive capacity and affinity for a broad sprectrum of ch~mical compounds. Organic compounds that can be removed from aqueous solution by active carbon include phenol~, cresols, alkylbenzen-sulfonates, nitroch-lorobenzenss, chlorinated paraffins, butadiene as well as certain synthetic dyes, insecticides and fungicides.

As an additional benefit, further removal of contam-inants ha~ been observed as a reault of biological act-ivity in carbon filter beds. It is thought that the highly adsorbent carbon surface actually enhances the growth of biological organisms because of its large surface area and its capacity to hold nutrients.

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_,_ Within reeent years, a large naturally oceurring dep-osit of earbon possessing properties similar to aetivated earbon ha~ been located. As a result of thousan~s of chemical tests and praetieal application in the field the result~ ~eem to indieate that the natural active car-bon may be as effective as the synthetically produced aetivated earbon in waste water purification of both organie and inorganie contaminants. If 80, b-eause the earbon may be produced at a fraetion of the eost of high qrade aetivated carbon, the dramatic eost reduction will allow many new uses in water purifieation needs, prev-iously found eeonomieally unfeasible.

Unlike ~ynthetie aetivated earbons the test results elearly demon~trate a significant adsorption eapaeity of the natural form of aetive earbon!for most cations and ~everal anions. The test~ also sugge t adsorption capac-itie~ eomparable with th- best aetivated earbons in the ease of phenols.

The following table sho~s the value of the natural earbons in the treatment of eontaminants-Inorganie Ion Adsorption -- . :
One of the unusual properties of the natural aetive earbon is its aPParent ability to adsorb a variety of inorganie ion~. The proeedure followed in testing the ad-orption properties of the earbon involves (1) prePar-ation o~ ~tandard solution~ (2) sievin~ of the earbon to a V 4~ to 1/16H partiele 8ize~ (3) three different washing proeedures involving ~a) a distill~d ~-.
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~ater wash, (b) a HCl acid wash, (c) a NaOH base wash, (d) a base then acid wash-(ppm)Neutral Açid ~ase Base then Contact Initial Wash Wash Wa h AcidTime Hrs concentration Zinc 300~6 1-0 Zinc 300-3 3.0 Barium 30022 1-0 Barium 3005 2-0 Copper 100-08 4-5 6-5 1-1 Iron 10 51 3-7 1-1 1-7 1-5 Manganese 114 6-30 81.0 6~3 43.0 1-0 Chromate105-00 .2 1 1 1-0 Chromate10025 18-0 Sulfate 200250.00120.0 150.0 1-0 Phosphate 50 37-50 33-8 13-1 1-0 Phosphate 50 6-0 11-1 3-0 Chloride 30 32-50 Nitrate 200 249-00115.090.0 5.0 Nitrite 109 105-00 1-5 Cyanide 70 10-00 1-0 Cyanide 70 8.00 2.0 Cyanide 70 1-10 20.0 Ammonium 30 5.00 1-0 A~monium 30 2-8 4.0 1~79876 _g_ The results shown heretofore, clearly indicate a strong adsorption tendency toward~ most cations and thR anion~>
CNr, CrO~ and to some extent PO~ Both nitrate and phos-phate have been ~ignificantly removed by th- earbon ~hen a biological community is developed. The acid and base treated carbons appear to have ~nhanced ability to adsorb nltrates, pho~phates and sulfates. It should be point~d out that longer eontact times will probably lead to inc-rea~ed ad-orption since oquilibriu~ aPPear~ to require e~-ral hour~ g., ee chromate r- ults) in some case~

Organic Adsorption m~ following tudios have been earried out using phenol and nitrob-nzenQ. Ten gra~ of neutral washed carbon wa~
treat d wlth ten gr~m~ o~ pure nitrobenzen~ and ten gra~s of 90X ~queou- olution of phenol for one hour By weigh-ln~ th- earbon b-fore and after xpo~ure to the organie the followlng r~ ult- wer- obtalned~
g of organie ad~orbed/g of carbon .
Phenol 0.19 .
~ 20~NltrDb nz~ne 0.16 ~, :
, _ re~ult- eo~pare favorably with the result- o~
a tudy in ~hieh phenol and nitrobenzene wcre adsorb d on a~larg- ar-a eo~er¢lal ~eeiv,ated earbon. Thi~ activated earbon, ~hieh~po---s-ed~a~Ju~aee area of 1200 m2~g, ad-eorbed 0.094 gram~ of p enol/gra~ of carbon and 0.22 grams of nitrob-nz-n~/gram of carbon.

Th-~- r ult~how ehat th- natural earbon adJorpt$on of~th~e~t~o~organic- 1- ~qu-l to that of a high grade ntb~tic;~actlvaeed~carbon :~:
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The following tests were done to determine the treat-ment effectiveness of the natural carbon in which a biol-ogical community has built up~ and which had been in use in the treatment of meat-packing house wastes for a period of 26 months without regeneration or replacement.

Contaminant Removals- Before Treatment After treatment.
_ Phosphate (ortho) 65.0 ppm .08 ppm Pho~phate ~total) 85.0 ppm 2.1 ppm Biological Oxygen Demand 750 ppm lO ppm ''"' mi8 invention relates in part to Canadian Patent App-lication No. 228,069 Pil~d May 29, 1975.

I have outlined heretofore the disadvantagQs associated with the collection and treatment of solid wa4t and the loachat~s issuing therefrom, in both controlled and uncont-rolled landflll operations, and have outlined herein by laboritory te~t~ the benefits to be gained from the use of adsorbent natural carbons for ~uch landfill leachate treatment-, It i~ an object of the invention to provide a ne~ and improved proceQs for the collection and treatment of land-fill leach~tes issulng from both controlled and uncontrolled landfill operations, that will effectively remove a variety o~ contaminant- from the leachate.

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An important objective i8 to remove the greater percent- -age o BOD and COD from the leachates.

Another object i8 to remove from leachates the heavy metals therein.

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A prime obje~tive of the invention i8 to provide an ~07~376 adsorptive curtain wall of carbon to surround old land-fill operations, 80 placed as to intercept and treat the horizontal flo~ of leachate originating from the refuse therein.

An additional object of the invention i8 to provide a ProCe8~ for treating landfill leachate~ which will remove offenoive odours therefrom.

A still further ob~ect of the invention i8 to provide a procees for remo~ing harmful bacteria~ pathogens and 0 VirUBe~ from the l~ndfill leachates to prevent th~m from passing into the groundwaters.

Still other objects and advantages will become appar-ent hereinafter I have found that the a~orementioned disadvantages may be o rco-e and the ob~ective~ achieved by Providing treatment for the landfill leachatea as is shown and desc-ribod in the ~ollowing numbered drawings and description.

In accordance with the present invention, therefor, the landflll leachatea are treated with~n a prepared land~ill site compris1ng a drained impervious base, which i8 over-laid with an impervious liner, covered by layer~ of ad-~orbent carbon A plurality of interconnected perforated flcKible pipe4 are laid ~ithin the carbon, and serve to gath-r and conduct the leachate to the collecting ~ump- ~-, whi d ~xt-nd vertically to the surface of the land-fill me refuse 1B placed upon the carben, and in use the eachat-~pa~Qg~through the refuse and i~ conducted through the perforated pipe to the collecting well ~' ::
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7~76 and then pumped to a plurality of separat$on bed~, biO-logical treatment beds, and tertiary treatment beds for treatment.

Referring now to Drawing l of Sheet 1. indicated at 10 is surface water $nto which landfill leachates from a typical uncontrolled land~ill operation may be seeping.
Indicated at 11 i~ a vertical curtain wall designed to stop the horizontal flow of groundwater carrying leach-ates therein indicated at 13. The curtain wall ll comp-rising two vertical wall sections, an inner ~all indic-ated at B formed by perviou~ polyvinal chloride (PVC) heavy sheating on the landfill ~ide, and an outer wall ~onmed by impervious polyvinal chloride (PVC) heavy sheet~ng indicatod at 9 Indicated at 7 i8 shown an inner core of granular solscted adsorbent coal. Within the lnner core ~ection 7 leachate recovery well~ indic~tod at 12 are rqcessed into the base thereof. In practice the laach-ate-groundwat-r indicated at 13 i85ue8 from the land~ill area~ indicated at 14 and passe~s into the curt~in wall ind$cated at ll thro~gh the per~ibus^l~all indic~ted at 8 ~he lcachate i8 prevented ~ro~ pa~ing into the sur~ace ~ater indicated at 10 by the imperviou~ outer wall of the curtain wall indicat~d at 9, and i8 coll~ct~d therein for r~moval by ~ean~ of pumping the leachate from the well8 12 Re~erring now to Drawing 2 of Sheet 1, indicated at 16 i8 ~ well crosa section Indicated at 19 i8 land~111 refu~e wlthin which a ~ell 12 may be ~ited out~ide the curtain wall 11 ~he re~u e leacha~e 22 pa~s~a through the rigid p~rvious wall 21 to b~o~ the leachate 23 At 24 is the ~ump s2ction o~ the well and indic-~079876 ated at 20 is bedrock or base of the landfill area within the well. me leachate 23 i8 withdrawn from the well 16 through the pipe indicated at 15, at the bottom end of pipe 15 is a standard waterwell screen indicated at 18. The withdrawal pipe 15 is 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 i8 a solid base of undisturbed earth, into which a groundwater coll~ction trap i8 recessed, the trap is lndic~tl~d~ at 3Q. The walls of the trap 30 are ~ade of pervious material 31. within the traP is laid perforated groundwater collection pipes which are indicated at 27-Enclo~ed within the trap and forming a surround for the perforated pipe 27 are selected adsorbent natural coal material~ indicated at 29. On either side of the trap 30 i- plac~d optionally a layer of perviou~ ~and or natur-ad~orbent active carbon 29 to the top of the trap 30.
Overlying the ~olid base 26, trap 30 and level fill ind-ieae d at 28 comprising either perviou~ sand or naturalcarbon 29 i~ a thick impervious sheet of polyvinal chloride PVC) indicated at 31. A ~ix inch base cover o~ sQlected 29 naturally active adoorbent coal iJ laid over the entire landflll ~lte, into which leachate traps 32 are rece~sed at lntervals across the refuse disposal area 25. Perforated coll-ction pipes indicated at 33 are laid within the leachate ~rap 32 with a surround o~ selected naturally w tlve adsorbent coal 29. A solid layer of clayey oil 18 placed ov-r the entire working area of , ''"'' , . . ! , , , ' ~ ' ' ' ' '' . ' . ' . ' . ' ' . ~ :', ' " ' ' ' ' ' ' ', .

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the landfill as indicated at 34. At suitable ~paced intervals perpendicular well piping indicated at 35 i8 joined together with the leachate collection pipe 33 and sump 22 from which the leachate and sludge may be pumped- Indicated at 36 is the refuse of the landf$11 operation.

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

Referring now to Drawing 5 o~ Sheet 3, indicated a~ 40 is a landfill area, indicated at 41 is the leachate cQll-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 i8 received the leachate to be treated. ~ the leachate is carrying large amounts of ea-lly ~ettled solids, it is pre~erably pa~sed through a ettling tank, indicated at 44, to permit such solid~ to ~ettle out. Optionally the leachate effluent is treated ~with a poIyelectrolyte pr~or to the passage of the leachate lnto a biological treatment bed comprising a smaller : ~ :
~ sa*d sQction indlcated a~ 45 : ~ ~ .'.': ' .~

1079~76 and a larger filter s~ction indicated at 46. The first treatment bed is shown as a dual media bed as i~ indic-ated at 47, having a first smaller section of relatively fine f~lter material and a larger filter section of rel-atively coarse filter media. The difference in the part-icle sizings of the media may vary according to the nature of the leachate~ and the type and amount of pollutants therein. Pre~erably the particles in the longer section 46 are of materials of lower density than that o~ the smaller section 45 particles. The difference in the den~ity helps to maintain ~aparation between the sections particularly during backwashing operations. While th desirab}e size range of the filter media may vary as aforementioned, the particles of the coarse section 46 should be sub~tantially larger in diameter than those particles of the finer media in sQction 45- The coarse Particles may range, for ~xample, from about 1/8 inch to about 3/4 inch. me coarse section 46 should preferably have a depth o~ not more than about 12 inches and the level of the effluant 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 i8 preferably formed of a relatively den~e material such as silica sand. The particle size ~hould be subatantially smaller than the particle size o~ the coarse media in section 46. The sand may range in size from about 0-04 to 0-Ol inch- The section 45 should have a depth of at least 6 inches and preferably a depth of between abou~ 6 to 12 inches.

: -- , - , , 10'7~8~6 After a period of about a month or when a backpressure develop~ which tends to restrict the free flow of the eff-luent 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 adsorbent coal treat-ment media in the bed~ 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 carry-ing line indicated at 48 and returned to the se~tling tank indicated at 44 for gettling. me effluent from settling tank ind~cated at 44 i8 then passed into the biological treatment bed 47 ~n the direction through the ~maller sand filter section indicated at 45, to ramove any ~olid~ therefrom and then through the longer ~ilter section containing ~elected adsorb-ent natural coal c~rbon in coarse particle ~izings therein. Ablological community i~ d~eloped naturally within the bed and i~ enhanced by returning part of bacteria laden outflow from the bed to the inflow of the longer bed ~ection 46 for th~ purpose o~ inoculation. The removal of BOD and COD prod-uclng ingredients is carried out in the first bed~ indicated at 47 without the production of any odours therefrom by maintain-ing the effluent level within the beds below that of the ~op of the carbon indicated at 49 therein. As i~ indicated in a following table the bacterial content of total colifonm and 30 faecal coliform are r~moved by the selected natural carbon ~-1~7~8 in contact therewith. Provision i3 made ~or the removal of phosphate containing substances in the effluents by providing in the plurality of treatment beds a bed or a section of a bed which will contain a ~elected natural adsorbent carbon having an affinity for phoæphates in the effluents 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 through a second biological treatment bed 47 or a plurality of such bad9~ and i8 then passed into a plurality of treatment beds by means of carrier line indicated at 55, wherein tertiary treatment is provided the leachate effluent~ to remove any remaining pollutants therefrom. The tertiary treatment beds indicated at 48 contain a selected natural adsorbent carbon having an affinity for tertiary type poll-utants which may remain in the leachate effluents, to remove them there~rom. The treated leachate effluents are then discharged from the treatment bed of the treatment sy6tem by m~ans of discharge pipe indicated at 56 for discharge to surfaoe waters indicated at 52 or to be re-cycled to the landfill operation indicated at at 51.
The aforementioned water discharged from the final treat-ment bed will be of a standard of quality suitable and acceptable to pollutlon control agencies for such disch-arges. The backwashing of the system is carried out by means of the pump indicated at 50 and the water carriage lines indicated at 55.

An idea of the treatment effectiveness of a selected naturally adsorbent carbon in the removal of harmful bacteria from wa~tewater after such treatment may be seen from the following reportO

Excerpt~ from a letter (on file) concerning tests made by the B-C- Pollution Control ~ranch, as reported to the Chief Health Inspector, Capital Regional District, Vict-oria, B.C. Dated January 22, 1975-"Attached are the results of tests on the coal system of 9ewage treatment"...We ran the te~ts for our own inform-ation as to how the material worked on domestic sewage, however, we thought you migh~ be interested in the results-"

"Re~ Treatment of Domestic Sewage with Pulverized Coal.
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A high degree of reduction has been achieved for some parameters including total and faecal coliform levels-"---The degree of treatment provided by this system is better than level "A" of the "Minimum Requirements for disposal of Municipal and domestic wastewaters to sur-face waters"-"--July 3, 1974-T- Coliform Infl- 9-2x106 Eff- 9-2x104 Red- 99X
F- Coliform " 4-9xlO " 7 xlO ~ 99%

In summary the process of the invention involves the ~tep~ oft 1. Providing a suitable way of coll~cting and remov-ing leachates from both controlled and uncontrolled landfill operations-~798~6 2. Collecting leachate originating within a controlledlandfill operation by conducting the leachate by means of perforated piping laid within adsorbent coarsely sized coal, to recessed filter trap~ containing therein the coarsely siz~d adsorbent coal.

3. Providing a means of settling out solid~ ~rom the leachates by forming well sections extendin~ to the surface of the refu~e from the recessed filter trap where the well has a lower sludge sump and an upper effluent section.

4. Collecting the leachate within the well which origin-ates from the perforated piping, the filter traps and through the pervious wall of the Well8-

5. Removing the collected leachate from the wells in bothcontrolled and uncontrolled landfill operations by means of pumps and conducting it to a settling tank.

6. Removing any remaining effluent 601ids in the leachate by the addition to the leachate of an adsorbent powd-ered coal flocculating agent with agitation, and then - op~ionally adding as r~quired a polyelectrolyte sett-ling agent.

7. when found necessary removing the settled sludge from the well sumps and f~rom the settling tanX~and inter-mixing the sludge with a further addition of powdered adsorbent coal and recyling the coal sludge mixture back to the landfill operation.

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8. Passing the ef~luent from the settling tank into a dual media filter comprising firstly a smaller sand section wherein the sand particle~ have a sizlng ranging in 6ize from about 0.04 to 0.01 and i8 placed within the filter to a depth of between 6 inches and 12 inches.

9. The effluent i9 then pa~sed into a longer filter-section conta$ning therein coarse sizings of selected adsorbent coal having a range of sizings ranging from about 1/8 inch to about 3/4 inch, wherein the leach-ate organlc matter i8 oxidized by biological w tivity, and where the biological activity may be enhanced by re-inoculating the biological community in th~ treat-ment bed by re-cycling the outgoing effluent ~rom the bed back to the ~ir~t ~ection of the coal filter media.
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10- Maintaining odour control within tha treatment bed~
by keeping tho ~f~luent level in the bed below that o~ the top o~ the coal treatment media.

11. Sel~ctively r~moving the total coliform, faecal col-iform and pathogenic bacteria from the landfill . .
leachate by treatment with the ~elected adsorbent coal materials. `

12- ~oving BOD and COD causing pollutants from th~ :
landfill leachates by trea~nt with ~elect~d adsor-bent coal material~-.
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13. Providing tertiary treatment a~ a final polishing sta~e of leachate treatment to remove any remaining pollutant~ ~herein.

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 material~, for use in removing poll-utants from landill leachates.

16. Determining the pollutant content and concentration thereof by analysing the landfill leachates.

17. Selecting the most suitable adsorbent coal3 for u8e in the treatment of landfill leachates chosen ~rom the group of coals consisting of most ranks of coal and coal wastes excepting anthracite coal~ In deter-mining the coal suitable for use in the leachate treatment procedure thin sections of coal are exam-ined by microphotograph ~tudy to determine the phys-ical characteristics, the content of surface chemic-als and crystals thereon, and the adsorptivity of the coal to remove the polluting leachate contamin-ants as found by aforementioned analysis.

18. Cru~hing, pulverizing and sizing the selected coals to provide treatment sizings which may range from 3 inche~ down through -200 screen mesh Bize-:

`` 10798~76

19. Improving the adsorptive affinity of the selected coal by a proces~ which involves artif$cial weath-ering which comprise~ boiling the coal particles in water for from about 5 to 30 minutes, or sub-jecting the coal Particles to a ~team bath, or washing the coal particles with solvent solutions chosenfrom hot or cold water, an HCl acid wash, a NaOh base wash, or a base then acid wash. Then optionally drying the coal particles at a temper-ature of from about 100C to 200C for a sufficient period of time to effe~t the removal of the moist-ure and/ or easily volatilized subetances or gases therein, or from about 1 to 10 hours.

20. Providing selected adsorbent coal in si~e ranges ~uitable for use ~or the purpo~e intended of the invention wherein a sizing of ~rom about 3/4 inch up to about 3 inches may be used in the filter traps, a~ a cover for the landfill base, and for a coal surround for the perforated collection pipes within the controll~d land~ill operation.
And wharein a powdered sizing of the adsorbent coal is used in the treatment of the leachate effluent passing into the settling tank for use as a flocculating agent~ this powdered sizing includes all those pulverized adsorbent coal materials in which the maximum ~ize i8 that pa~ing a standard 200 mesh size screen- And wherein the sizing of the ad60rbent granular coal materials used in the biological 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 ~elected sizings within that range.

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21. ~ further additional step is the conversion of an uncontrolled landfill operation to a controlled landfill operation wherein a vertical lmpervious curtain wall i9 provided to surround or cut-off the horizontal flow of leachate iæsuing from the landfill operation, within which a second vertical wall of pervious construction i9 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 recessed ~nto the base of the landfill and the aforesaid inner core section ~eparating the two wall sections. The wells consisting of a lower sump section for the collection of settleable solid~ ~rom the leachate, and an upper section for the coll~ction of the sett-ling leachate e~fluent. The wells, extending vertic-ally from the recessed sump area through the landfill refuse and adsorbent coal treatment media to the landfill surface, are formed from rigid perviou~
non-degradable material. The leachate from the solid refuse percolates through the inner pervious vertical wall and thence through the inner core ~ection of adsorbent ~ranular coal and is then passed through the parviou~ rigid wall of the collection well, and, when the ~olids are settled therefrom the ~ettled eff-luent i8 then pumped from the well to a settling tank and i8 then treated by the aforementioned leachate proce~8 outlined heretofora.

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79!~6

22. Backwashing the biological treatment beds and the tertiary treatment bed~ when a backpressure is found building up within the beds which restricts the free flow of the leachate effluent therethrough and conducting the wash-debris from the beds back into the settling tank.

Having illustrated and de~cribed a preferred embod-iment of the invention, it should be apparent to those skilled in the art that the invention permits of modif-ication in arrangement and detail. I claim as my inven-tion all such modifications as come within the true spirit and scope of th~ appended claims.

Claims (4)

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

1. In a landfill-leachate treatment process, the imp-rovement in treating solids in the landfill leachate which comprises:

(a) mixing leachate as received from the landfill collection wells with adsorbent powdered-coal flocculating agents, (b) separating the solids and liquids in the mixture of coal and leachate and removing the solids from the liquids, (c) adding a polyelectrolyte to the coal-leachate mixture as a settling agent, and (d) filtering the solids after addition of the ad-sorbent powdered coal flocculating agent and polyelectrolyte settling agent, through a dual media treatment bed containing in a first section a dense filter media comprising silica sand having sizings which may range from between about 0.04 to 0.01 and in a second section a media of alarger diameter sizing comprising selected ad-sorbent coal having a range of sizings ranging from between about 1/8 inch to about 3/4 inch-

2. A leachate treatment process as set forth in Claim l wherein the solids are separated from liquids in the mixture of powdered coal and leachate by passing the mixture into a settling tank, adding an adsorbent powd-ered coal flocculant thereto, and allowing the solids to settle therefrom and thereafter removing said solids and coal mixture from the bottom of said tank.

3. A leachate treatment process as set forth in Claim l wherein an additional polyelectrolyte settling agent is used and added to the said leachate to enhance the degree solids settling in the said settling tank.

4. A leachate treatment process as set forth in Claim l wherein adsorbent powdered coal is mixed with the incoming leachate to the settling tank in the proportions of from between about 1/4 lb to about 10 lbs of said powdered coal per 100 gallons of said leachate.