DE1926969A1 - Process for the chemical removal of phosphorus ions from waste water - Google Patents

Description

North A me r Loan Rockwell Corpora oi on ', KL Se ^ uudo, California,

- ^r; '' - ■ V.3 CA.

Vjtu'ahren zur che.aiscrun removal-of phosphorus ions

sewage

The invention -relates, itself, ayf. a, method of chemical Removal of Phosphbrioriöfi from "sewage.

Many, .Seen ,, pVlÜsse 'and BeebucKtö'n, i ^^ der'ih d see from loading ^; .population centers are for ^ humanity ... because of - the influx of nletit. can no longer be used on prepared or incompletely treated urban or industrial wastewater containing simple and condensed phosphates. These salts require radical changes with regard to the biological treatment of this water. Finding cheaper, more reliable and more effective Procedures for removing phosphorus from sewage are essential to the restoration and maintenance of these natural sources of water supply.

909848/1179 'ORiGlMAL! MSPE

- 2 - U jJ> -r

To remove Paospnaten- from Hbwäs.3 ..r \ i airiu vi ^ lc biologio jne and 'Ko.r.oiniarte chüi.viaca-bioio ^ ioun sen applied or vorgwocaiageri woi'd- ^ a. Uas ca /.iläo from Pnospnat iac in great.n mass a: r; he ßemitzun, voa j is en and AlUi.iiriiu.nsaizen been researched, luer ini ^ üiiüiiö successes oei in the treatment of floodplain- i ' u '. »ufd ^ j-ricat ^ :, · in particular in Benu'ozu.'i ^ from Alu; .iiniu..i- ur.d jüü-aaa Lz-, n ^: in a three-step weaveri'aaren. Gowoal " ui ^ s ^ V u'i ^ .it'iäoUjio; ä have been successfully an ^ ewendec unu vo-ueii-aaf '., · .. - \ ier.K ... ia Ls ■ have, suffer disse '/ ^ rfaarenswuison jedoün whom ilacn share.3o is i; n general:; iGinea aiii oec excess of caeräikalische zur wirlisamei-i ^ auf-jrLj ^

Phosphate required. Ausaerdtjai is ii all ^ e ^ iciaia -iiae careful pH-Ε ins ^ eIlUn ₀ necessary u -.- i sooa L Ko-apl ^ xbilduntjeh as well as a precipitation of hydroxide to ν ην.ΛχΛά ^ ΰ. Fdrn ^ r are the üo ^ ioaen Verfanren Roi.inlisiert- and 'rela ^ iv ^; uiiv / irxsa. ^, '· because from economic irwagungeii the fall ^ s :> L \ Gt: L i:, i atl ^ e- :: iinen has to be regenerated.

The aim of the present ¹ experience is the development of a very effective process for the direct precipitation of priopes from wastewater using a rare earth salt.

More particularly, the invention relates to a method of nefishing Removal of phosphorus ions from dimensions and is dadurca marked ty that these are worth with a trivalent rare Earth ion with the formation of an insoluble rare earth precipitate In the wastewater are implemented "and this" then precipitate * from which water is separated.

Ifach a further "feature of the invention _{: i} : vjird 'di-i3e * HUsfällung nachfolahd' for the regeneration" of the rare earth precipitation with strong acid or with strong acid or with strong alkali, preferably * in "an alkali regeneration procedure" a concentrated aqueous solution 'of sodium hydroxide oüir Käliumhydroxyd, ± n "a · the' Regenerieruhg geeigrte ten'AVt-Uend ^r w ^ eiäe"

BAB ORIGINAL

~ 3 ·· w l> ö ^

treated. This alkali regeneration medium can be used in the process eba.ifalis can be recovered by treating the formed Alka Liriuitällpnosphat with lime, and used again will.

The currently uoueren.Kosten the lie of a rare Erdenchemika existing novel precipitation:; iittels ergleicn in V :: iit previously used for FaLlungsmit "one is from wirtseriaf" lic, en Jesichtspunkt from disadvantageous feature, Durca the im a ilgeuieintn from the Consideration is given to using such precipitating agents, however, it has been found that the process of the invention eliminates many of the disadvantages associated with the previously known processes, and produces a more complete, higher-performing, and more accurate, phosphate low Control or adjustment measures are not required. These features, together with the regeneration stage associated with the process, make the process according to the invention economically significant in comparison with the processes previously used. The method according to the invention therefore offers the possibility of having a relatively cheap chemical method for reducing the phosphate content of wastewater below 0.1 mg P / liter and with a negligible remaining cation concentration of remaining precipitant.

According to the preferred embodiments of the invention lies the trivalent rare earth precipitating agent that contains the phosphate Wastewater is added in the form of the chloride, sulfate or hydroxide of the rare earths. The ions of the Rare earths react with the simple or complex Phosphatipnen with the formation of an insoluble phosphate precipitate of the rare earths, preferably by filtration is removed and leads to a practically phosphate-free wastewater. The starting compound of the rare earths is then advantageously by treating the insoluble precipitate regenerated with a strong acid or with strong alkali.

1179

- k - N j34

During the regeneration aas insoluble Pnospnat d ^ r rare earths, preferably with concentrated aqueous Matriu,; inydroxyd, in general at -ine.ri pH less than 11 for the conversion of the Pnosnhats the rare earths into an insoluble hydroxide of the 3eltonenrden and production of soluble sodium phosphate benandelo. The unloslicne hydroxide of the rare earths is oration of the solution containing dissolved Natriuranydroxyd and Natriumpnosphat entnäLü, uurcn Fi L or separates a entsnrechende process measure from _o e. The rare earth precipitate is then either added to the rare earth hydroxide directly to an untreated acidic water or first by reacting the rare earth hydroxide with hydrochloric or sulfuric acid for the purpose of reforming the soluble chloride or sulphate of the rare earth reused in the process as a soluble precipitation agent from rare earth salts.

The dissolved sodium phosphate; containing sodium hydroxide solution can be treated with lime in order to restore the regeneration agent from sodium hydroxide and to produce an insoluble precipitate, _{e.g. Ca 10} (OHJo (POh) - back fabric ze Na tr iumhydr oxy d solution is returned to circulation in the process.

For economic reasons, all process steps are im generally carried out at ambient temperatures. With the vote individual process stages, however, especially without regeneration, the temperature can be increased to increase the reaction rate or the solubility of the constituents.

The only figure in the drawing is a scenic snapshot again, in which the treatment of a phosphorus-containing waste ice for the purpose of precipitation of the phosphates contained therein and the subsequent regeneration of the reagent from rare substances Grounding using an alkali regeneration process will be explained.

909848/1179

BATH ORIGINAL

1926989

.- 5 - N 5

The present invention is broadly based on a

Varfanren for the chemical removal of phosphorus ions from waste water through direct precipitation of these ions through conversion with a precipitant from trivalent rare ürdeniori directed to form an insoluble precipitate. That Precipitant is then used to renew G / üraucri through an Alitali regeneration and recovered Rückoi longitudinal process.

To explain the preferred embodiment of the invention according to the single figure of the drawing with reference to the Removal of orthophosphate from Aowwasser by failures with a.a soluble lanthanum salt are described. It is there however, assume that the term orthophosphate is exemplary for dissolved phosphate ions in general and that other phosphate compounds are also to be recorded, such as condensed phosphates and polypnosphates from to Part of organic origin. In the same way, the lanthanum compound, such as the lanthanum chloride, sulfate or hydroxide, although generally preferred, is just one example of general salts of rare earths, which are used for sicn or as Mixture of rare earth salts can be used. Under practical procedural conditions, it is for most Purposes simpler and more economical, a naturally occurring To use a mixture of rare earths containing lanthanum mixed with other rare earth elements, as a material for the rare earth salt, to be used as any pure rare earth salt.

The precipitation and regeneration reactions given as examples can be shown schematically as follows become: ■■

La * ³ + POj |. ~ ³ (or HPO ^ " ² ) LaPO ₁ ^

+ 3NaOH (aqueous! PH ^ 11 ν La ( OHU + Na ^ POj ₁ (aqueous)

90 9840/1179

. - 6 - II

6Na, .PO, (aqueous) + 10Ca (OH) ^ Yes (GH) (PO) - +

The industrialized process is particularly suitable for a three-stage chemical treatment of urban wastewater for the practically complete removal of its phosphorus content, whereby the pnospnate which occurs in the second stage of a water treatment plant is precipitated. In a typical treatment of d cadciscjien wastewater, there is a first clarification stage for the removal of solid components as sludge, which is followed by a second treatment, to which aeration, biological Gxyaacion of organic material and a Nicderscnlao3n further solid Suus ^ no are dancing. Jurcn these two stages are common irn a Ll. ^ .- neinen not more than about 20, O of the waste water Ln '/ ^ oraancifc ien phosphorus eritfennt. May be 3o entnäLt the flow of the second 'n .- ^ oddi.n ritationssufe typically a PhospaorKonzenjra cion vori j to -jQ -Λ ^ / LLier phospnat Ortno-in the form of and konaensisruön Pnospriaten as pyrophosphates and polyphosphates ^ the biological origin .

The trivalent rare earth ion as a precipitant, preferably lanthanum ion with an admixture of other trivalent rare earth ions, can, for the sake of simplicity, be in the form of its chloride, sulfate or hydroxide. Although lanthanum hydroxide is relatively insoluble compared to lanthanum caloride or sulfate, it is particularly suitable for use in treating urban sewage which is acidic. The chloride salt is advantageous for treating non-acidic wastewater. Although lanthanum salts are generally preferred because of the more basicity of the lanthanum ion, any trivalent rare earth ion or ions in the form of a suitable salt or salt mixture can be used in the practice of the invention. With regard to the expression "rare earths", reference is made to the lanthanide series of 15 elements with the atomic numbers 57 - 1 and yttrium with the atomic number, which have similar properties to the rare ones

909848/1179

BA © ORiGfNAL

- J - - N uJ'i

Earth auiwjiut una in nature -., It eieri 3elre :: ~ n ErcUn ver _f ; ese 1 Is cha Γ c "before» co .int. The so-called: ', r.nton leicatsii rare earths, di- C ^ rjrur ·:. (Λ te: .muinierr; ^ i '- Jj)), w-mie.-i weighed inrer basicity "i. = Ia li. ^ G r.ii.ioii, ^ igen about d -" - n so ₀ poor heavier rare j] i "de ^v :.;! ^f tallon dir /.turiu^igrunpe (A tomnu-rnern jh - / 1 J, preferred. IL.Lsr üen ba tsUeulicn ^ i Aro «itsbedin _a untSen one. ■ Everyday W'jruc :, jeuocu .jcwöiinlicii oil · -, pure 3-3'l.tsiien.Lrdensalza nicnt aiigevj '., - iivit; t, sona.rn there are in Ha.idol unälTylicrie K-onzenira ie or G "iiscae bequ.j-ner and, ^^ ei ^ net ^ r. Suitable Hineralquellc .; are, -! oaaziv, Uastnasit and Kineralaofalle, which will age at the Veraro-ditua .. ^ \ on urannalLiijcn -irz ^ n. Lantnari liiacnt or-vja 'a- ..j ü <. 3 Κ · 3 tionen ^ eiialLes from Monazite. 3astnasit, dc.L ' :: ieiir contained as j> 0 p of the cations as lanthanum, is easily _{sold in the} inexhaustible, leached and calcined forin. , veil, jedoen vine ias liinzelne ^ unende study of the erf inaun ^ Sfj-i iaßii V-erfanrens primarily using lantnansaiz as Fällun ^ smit ce L and aqueous-Ortiiophospha tlösunc ^ n ^ eniaeat is said to be the preferred embodiment : n an Haad of the reaction between drewer oigei a Lanthanion and Ortnoposrshation are described.

After the Zeionnun.;. a phosphorous-containing wastewater 1, generally an Aolauf from a second stage of a treatment plant, with a:? i trivalent Laithanion 2 in a suitable reaction vessel · 3 u: no; ese tz t. Tananaev and Mit. have given a solubility product ^ t (^ _τρ ) of J, '(j χ 10 ^ for LaPO .. They also have a precipitate v-ea from 9LsPOi.'La (OH) ₇ * 23HqO when using an excess of La reports that while LaPO ₂ , * j5Ho ° is precipitated when stoichiometric amounts La - * and POjb are used, it is particularly advantageous to use s tochiOinetric amounts of up to an excess of trivalent cation for precipitation in order to produce an in To obtain the smallest possible mass of hydrolyzed simple product, ie a ratio of cation to anion between 1 and 1.5 · Depending on the other process stages, however, a ratio of cation to anion ranging from 0.5 to 5 is generally preferred.

909848/1179 BAB orig! Nal

- 8 "* N ^l jok

The precipitated LaPO ^ containing waste water is drawn from the boiler j5 through a conduit 4 to a filtration system ¹ J to the insoluble LaPO to collect. If desired, other suitable separation measures, such as decanting or centrifuging, are used. The treated water is drawn off the filter ^l j through a line ό. In a perfect method ernäLt & guidance n at this triple Präzipitationsbenandlung a reclaimed water, a nil Pnosphorgenalt of less than 0.1 mg P / liter. This reprocessed water can no longer be treated so that it can be reused as a source of drinking water in Betracut, or it can be drained directly as purified wastewater, which is then no longer a source of pollution, e.g. as an inlet to the groundwater dics-r process stage for phosphate removal

+ "5

becomes üD ·. Rscimssiges La, which was used as a precipitant, precipitated as LaPO ₄ ⁰ I) H ₂ O odex as a mixed hydroxide phosphate, for example as JLaPO ₄ 'La (OH) -' 2311.0. Therefore extends the Laritnarii "Ueck _o ewinnung whether initially equal, have been stoichiometric amounts or überscnUssige ewtndet ax ^, substantially completely before the aufbernioe ^ e water is continued for reuse.

Although the chemical failure of a three-stage water treatment is used as the primary method of removing Pnospaat from a second-stage run, the costs involved are relatively high, particularly because of the excess amounts of chemicals that were previously required to be treated in Wirlcsauer would like to remove 90 to 9 ^ _f j of the phosphorus content from the wastewater. Daxier is oei a wirtscjiaf ollen arbüitinden Verfa ^ r ^ n '-ine regeneration üe-s cnernischen precipitation .ni-ctels in allgeineiii'Lü erforderlicxi. The method according to the invention can easily be adapted to and is particularly suitable for -jine-solcn "regeneration measures.

! La tweüur is υ cine acid treatment, eg with HpSO ₄ , or a lisout; dei ia ad ment for regeneration ge ^ i ^ net. An initial

.9 0-9848 / 1179

BATH

• Borrowed, acidic treatment of the LaPO ₂ , with HpSQ ₁ , leads to a solution of a mixture of phosphate and sulfate with relatively low levels

+3
pH. The La is precipitated from this solution as oxalate, which is heated to form the oxide, which can then be used again to remove phosphate from the wastewater. In such a recovery process, HgSO ₁ and oxalic acid (or sodium oxalate) are consumed and represent part of the process costs. In the alkali process, however, in which Ca (OH) _{2 is} consumed, the product formed, e.g. Ga ₁₀ ( OH) ₂ (PO ₁ , L.

According to the drawing, the LaPG ₂ , precipitate is fed from the filter 5 through a line 7 either as a solid substance or in the form of a slurry to a reaction vessel 8, in which the precipitate reacts with a concentrated aqueous sodium hydroxide solution 9, which is in the Reaction vessel 3 is entered through a line 10 * Advantageously, increased temperatures which are below the boiling point of the solution are used in this process stage in order to accelerate the reaction rates. Temperatures between 40 and 90 ° C are suitable. The extent of the conversion of LaPOu into La (OH) - * depends on the concentration of the NaOH solution as well as on the reaction temperature and the reaction time; away. The appropriate assignment and optimal correspondence of these variable quantities can easily be determined by routine tests. In general, a greater than stoichometric amount of sodium hydroxide solution with a pH above 11 is _{preferred for optimal conversion of the LaPO 2} , preferably at a temperature between 70 and 90 ° C. When working at room temperature, a suitable reaction time can be 30 minutes to about 10 hours, an increase in temperature making it possible to shorten the reaction time. Unchanged solid LaPO ₂ , is carried out through the subsequent process stages and

909848/1179

can then later be separated and used for regeneration nii'c alkali be entered in the boiler d a.

The addition of lime, which is cheap, is preferably done on this point of the run to reform sodium hydroxide and to decrease the phosphate concentration. Some phosphate, that is dragged into the circulation beyond this point has little effect on the final phosphate content of the treated wastewater. Hence a practically complete removal as opposed to the water treatment step in the kettle > not required.

The sodium phosphate-sodium hydroxide solution in kettle B, which contains relatively insoluble La (OH) -, is passed through line to a filter 12, where the precipitated La (OH) - is removed. The sodium phosphate-sodium hydroxide solution is then drawn off from the filter 12 through a line 13 to a reaction vessel 14. A lime deposit 15 is introduced through a line 16 into the reaction vessel 14, in which it is reacted with Na ^ PO ₂ , an insoluble calcicurakoinplsalz, ζ .3. Ca ₁₀ (OH) ₂ (PO ₂ ,). ', And the sodium hydroxide is simultaneously regenerated. The mixture in the vessel 14 is passed through a line 17 to a filter 18 where the calcium "is separated phosphate complex and at the same time the sodium = hydroxide through line 19 to the Natriumhydroxydvorratsbeal? 1 9 for re-circulating in the process returned v * lru. < The calcium phosphate complex formed can be regarded as a waste product or used as a supplier of lime and phosphorus for agricultural purposes.

Relatively insoluble La (OH) -Z, which has been formed during the alkali regeneration of LaPO ₂ , can be added directly to the acidic wastewater. This allows the phosphate to be neutralized and removed in one step. However, according to the most important recovery process route, the La (OH), in an aqueous solution of LaCl-, or La ₂ (SO ₂ ,) -, is under

909848/1178

Using suitable hydrochloric or sulfuric acid transferred. The U .-. Rwandlung in the chloride salt is generally used because of its greater solubility. Thus, a mineral acid, for example HCl, is introduced into a boiler 20 through a line 21 into that reaction vessel 1 22, in which the acid _{reacts with the La (OH) 7} which enters the vessel 22 through the line 'd'j from the Filter 12 has been entered. The reconstituted lanthanum chloride is then returned through line 24 to the lanthanum storage tank 2 for recirculation in the process.

The following examples illustrate di · ¹ invention and give-yn the beneficial results again obtained by the erfindungsge.nässs process. The examples are supposed to be the j £ rfindun _o not υ v? gr e nz -ι ri.

example 1 Precipitation

A series of 1.2 experiments was carried out in which solutions of lanthanum nitrate were added to phosphate solutions with stirring, the HagHPO ^ solutions with concentrations of 1 or 50 mg P / liter, solutions with a pH of 5, (, ο and 9 were prepared by adding HpSO ^, or NaOH solutions of suitable concentrations. The lanthanum additives had a 5% excess over the stoichiometric amount, and one of the approaches was carried out with a 50% excess Stirring was continued for about 50 minutes, the precipitates were allowed to settle, and the solutions were then filtered. The resulting precipitates and filtrates were analyzed.

When applying '; i! I-; s 5 / üigen über causa es an La ^ over the S'töchio-netrisc.ic- slopes the phosphate-pnoshror-concentrations were from 1 m _o / liter to less than 0.02 mg / liter one

809840/1179

ORJGfNAL

ν 1926369

/ · - 12 - ^: N 584 '-

pH decreased from 8. The final concentrations were about;

.0.03 mg / liter at pH values of 7 and 9. This corresponds to a 97% or Beeslen removal of the phosphorus. Back - _t retarded La ⁺ ^ was generally wehiger than 0.05 mg / liter corresponding to an entrained quantity (loss) von'weniger than 1%. At phosphorus concentrations of 50 mg / liter, the final concentrations ranged from a highest value of 0.9 mg / liter (98 % removal) at pH 0 to a lowest value of 0.07 mg / liter (99 * 9 $ ige removal.) at pH 8 * Lanthanum entrained was less than $ 0.09 even without precipitating as, La (OH) - ,,.

With a 50% excess of La ⁺ ^ and 50 mg P / liter and a pH of 8, the final phosphorus concentration was less than 0.02 mg / liter ( 9 % removal). Lanthanum carryover was reduced less than 0.09 ^ä ß> by precipitation as La (OH) ₁₅ and by a pH of 12 ^· (6,4- ^ were before the pH ßins distribution in solution remained) *.

Example 2

R eg ene r 1 er ung ·

4 of the obtained according to Example 1 were digested with Lanthanphosphatniederschlägen JQ temperatures between ⁰ and 90 C in hot concentrated NaOH having a pH above. 11 The examination of the remaining, plague substances with the help of the Höntgen radiation diffraction and the X-ray fluorescence showed that these solid substances essentially consisted of La (OH) -. The residual phosphorus in the powder substances was of the order of a few tenths of a weight. -fi. Practically all of the phosphate had therefore been converted into a soluble form, and analysis further indicated that practically all of the phosphate remained in the precipitate.

It can be seen that the invention is subject to "numerous" variations "

909848/1179

ORIGINAL INSPECTED

- 13 · * ■ ■■. ■■. N

'round durcagefüßrt WoI ¹ UJn ttann, oxine from. These changes with regard to the temperature, the reaction time and the concentration of the reaction participants are partly due to the special lantnanide mixture or the mixture of other rare earths used as precipitants, the type and concentration the substances present in the effluent, depending on the nature of whether they are present in dissolved form or as suspended solid substances, and the like the method according to the invention can also be used for the treatment of phos pha thai conditions waste water from industrial plants or accumulated runoff water from the agricultural sector with Kotizentrationsberelohen for phosphate from around 1 ppm to IQQO ppm and higher.

Patent claims

809848/1179 MB

Claims (1)

Claim patents? 1. Veffahreri for the chemical removal of Phosphorioric-n from wastewater », thereby identifying that these ions with a trivalent rare srdenion. forming an insoluble rare earth coating In de-ri ad- _; water are converted, and this precipitation is separated from the -; ^ wastewater, -; _; ;? : v. 2. The method according to claim 1, characterized * that the ionic ratio of rare cation to phosphorus anion / which is used in the WWl treatment reaction is 0.5 Ms 5, - 3>; Method according to Claim 1 or 2, characterized in that that the rare earth precipitate ftäü ^^ äeiiileh lanthanum chloride, -sulphate or -hydroxide contains * r ^. Method according to claim 1, 2 or>, dadurea characterized, that the rare earth precipitation is a Qemish of Salts of the rare earths is * that from a lahthan-containing Mother mineral has been extracted. : 909848/1179 BATH 5, method according to any one of claims 1 to A / characterized in that the unliJsiLicae rare earth precipitation, which has been separated from the waste water, for the purpose of regeneration. The rare earth precipitate is reacted with a strongly acidic or alkaline regeneration agent. 5. The method according to claim 5 # characterized by * that " - The rectifying agent is a concentrated aqueous solution of sodium hydroxide or potassium hydroxide 1st, 7. Circulation proceed after a 4 a nsirtiche 1 to 6, thereby characterized that the phosphate precipitation and that practical Phosphate-free wastewater is obtained separately; the phosphate precipitate obtained is more than stoichiometric aqueous sodium hydroxide solution with a pH higher than 11 with the formation of a rare earth precipitate " hydroxide in a sa triümphospha t-sodium hydroxide solution is implemented, the precipitation from rare earth hydroxide and the said sodium phosphate-Na triumhydroxyd-liösung Separately, the precipitation from rare earth hydroxide is isolated with hydrochloric or sulfuric acid with the formation of a corresponding soluble salt of the Rare earth is implemented and said soluble salt of the rare earth in the process for further Circulation is returned, 3. The method according to claim 7j dadurca characterized in that the rare earth phosphate precipitate contains predominantly lanthanum chloride or lanthanum sulfate. 9. The method according to claim 7> characterized in that the wastewater to be treated is acidic and phospiafchaltige entaalt the oeltene Eruenausfällung Mainly lanthanum. 10. Ancestors according to claims; 7j. 3 or 3, marked with: i- 800848 / 117S bath η · η that uio isolates. NatriuLipnospnat-iJa'jriuranydroxyd-Lüsung with KaIk under ¹ Formation of a CalciUdipnosphamieders cn La ^ s and Re ^ erieriarun ^ der Ilatriuiahydroxydlösurie, · implemented vjiru, the, -, eiianriij-ce Ga lciu.anacosp ^ rierto Wa triu.anydroxydlösung in the Vurfanrjn.] further "J-nlauf zurücic" will result. 909848/1179 ORiGSKAL