6

BIOLOGICAL TFLEATABILITY AND INHIBITORY EFFECTS OF A TEXTILE WASTE CONTAINING CAPROLACTAM

2 3 by P. Christopher Brown', Gregory D. Boardman4, Raymond B. Reneau , and Thomas W. Simpson

Pntroduct ion

Al l ied Corporation's f i b e r p lan t a t Chesterf ie ld , Virginia, is one of the world's l a r g e s t producers of Nylon-6. Nylon-6 r e f e r s t o a polymeric material, t h a t i s manufactured from caprolactam, a cyc l i c amide of s ix carbon atoms, nine hydrogen atoms, and one nitrogen atom. The wastewater generated a t &&e plant contains r a the r high l eve l s of organic nitrogen due t o the presence of caprolactam, and is present ly handled i n a treatment t r a i n consis t ing of th ree holding ponds and a land appl icat ion system. followiny paper was undertaken t o evaluate the f e a s i b i l i t y of using act ivated sludge as a pretreatment process t o decrease t h e nitrogen loading on the land appl icat ion system.

The work described in the

There i s information i n t he l i t e r a t u r e which indicates t h a t caprolactam can i n h i b i t t he growth of microorganisms (2,4,6,7,12,13). Also, it has been reported t h a t n i t r i f i c a t i o n is repressed a t caprolactam l eve l s i n the a rea of 100 t o 1000 rag& (13). A t the lower end of t h e range the process is s l i g h t l y inh ib i ted , while a t t h e higher caprolactam l eve l s v i r t u a l l y no n i t r a t e and l i t t l e n i t r i t e form. These concepts were, of course, important t o consider hecause i f caprolactam leve ls i n t h e in f luent streams t o the biological reactors of t h i s study were too high, the t rea tnent processes could be inhi- bi ted. In addi t ion, t o accomplish the goals of t h i s study it w a s necessary t o minimize n i t r i f i c a t i o n , so t h a t the re lease of nitrogen from the wastewater i n the form of ammonia could be maximized.

Anderson -- e t a l . (1) a l so studied t h e use of act ivated sludge t o t r e a t the wastewater from Al l ied ' s t e x t i l e p lan t , Su t t h e r e s u l t s of t h a t e f f o r t were confounded by excessive evaporation from the reactors . presented herein i s therefore an extension and a refinement of the work i n i t i a t e d by Anderson st. (1). a t ten t ion was di rec ted a t t h e mass balance of const i tuents i n reactors and more parameters were monitored. caprolactam and const i tuents of the adenylate pool, cons is t s of adenosine mono-, di-, and tri-phosshates (AMP, ADP, and ATP). In recent years it has been suggested t h a t a r a t i o of the adenylate components can be cor re la ted t o the inhibi tory/ toxici ty e f f ec t s of an agent. One of the more C O ~ O R r a t i o s considered i s re fer red t o a s energy charge (EC) and is calculated a s follows:

The invest igat ion

More spec i f i ca l ly , i n t h i s study more

Among t h e addi t ional parameters measured were The adenylate ~ 0 0 1

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1 'Graduate Student, Civ i l Engrg. Dept., V?I&SU, Blacksburg VA, 24061 2Assoc. Prof . , Civ i l Engrg. Dept., V P I & S U , Blacksburg, VA, 24061 3Assoc. Prof. , Acjronomy Dept . , V P I C S U , Blacksburg, VA 4Asst . Prof. , Agronomy Dept. , V P I C S U , Blacksburg I VA

24061 24061

1

2

(ATP) + (ADP/2) (ATP) + (ADP) + (AMP)

EC =

I Thus, a secondary object ive Of t h e e f f o r t was t o determine i f EC could be cor re la ted t o t h e performance of the act ivated sludge reactors .

me experimental approach and procedures f o r t h i s research a r e described in the n e i t sect ion.

Overview of Research

me experimental procedure f o r t h i s study w a s divided in to two pa r t s . F i r s t , batch experiments were performed t o determine the inh ib i tory e f f e c t of caprolactam and thereby s e l e c t an optimum leve l f o r b io logica l treatment. Secondly, aerobic continuous flow, ac t iva ted sludge reac tors were used t o evaluate t h e b io logica l t r e a t a b i l i t y of the wastewater and f o r t he development of b iokine t ic constants.

Seed organisms were obtained from a p i l o t scale, ac t iva ted sludge system a t the All ied Corporation Plant i n Chesterf ie ld , Virginia. This cu l ture had been u t i l i z i n g caprolactam a s i t s so le source of carbon and nitrogen f o r approximately two years, and w a s therefore assumed t o be w e l l acclimated. Enough sludge w a s removed and t ransfer red t o VPIcSU t o f i l l th ree laboratory- scale, ac t iva t ed sludge reac tors (volume of each 8.0 o r 8.6 L).

Three 208 L (55 gal ) drums were l ined and then f i l l ed with wastewater from one of t h e holding ponds a t the All ied Plant. t o avoid having t o sample more than once and r i s k t h e chance t h a t the waste- w a t e r would change in composition. The wastewater w a s s tored a t room tempera- t u r e and the following cha rac t e r i s t i c s w e r e monitored frequent ly t o ensure t h a t t he wastewater remained s tab le : t o t a l organic c a r b n (TOC), chemical oxygen demand ( C O D ) , t y t a l Kjeldahl nitrogen ("1, n i t r a t e (NO-) , n i t r i t e (NO;), and ammonia (NH4 + NH3).

Aerobic Batch Experiments

Ample volume was obtained

3 (See "Analytical Procedures" sec t ion ) .

Waste sludge from t h e th ree bench reactors was composited t o make up the biomass f o r t h e batch experiments. a t 10,000 R P M f o r t en minutes a t 20'C. r e su l t i ng c e l l mass d i lu t ed t o one l i t e r . of t he biomass solut ion w e r e t ransfer red t o each o f - f o u r 500 m l Erlenmeyer f lasks . Twenty-five m i l l i l i t e r s of caprolactam standard o r d i lu t ed wastewater with 50 t o 10,000 mg/L of caprolactam was then added t o each f lask. addi t ion, a s u f f i c i e n t volume of a KH PO so lu t ion w a s added t o ensure a 2 4 BOD5:P r a t i o of a t l e a s t 100:4. temperature ( 2 2 ' + Z ' C ) , allowed t o s t a b i l i z e t o a PH of approximately 7 . 5 , and aerated t o provixe oxygen and mixing.

The composited cu l tures were centrifuged

W o hundred and f i f t y mi l l i l i t e r s The supernatant w a s removed and the

In

The react ion vesse ls were kept a t room

Each batch t e s t ing period l a s t ed f o r two hours. A t t he beginning of each t r i a l the m i x e d l iquor suspended so l id s (MLSS) of each reac tor was Zetermhed

r

3

and samples f o r t o t a l adenylates (ATP, ADP, and AMP) , soluble COD, and soluble caprolactam analyses were withdrawn. After one hour a d a t the end of the two hour t e s t i n g period, samples were again taken f o r t o t a l adenylates, COD, and caprolactam.

Inhibi t ion curves were developed f o r both caprolactam standards and wastewater t o determine i f t h e r e were any other inh ib i tory agents present i n t he wastewater other than caprolactam. Experiments with each d i lu t ion or standard were generally-duplicated, bu t i n t h e more cr i t ical areas of the inh ib i t i on curves t r i p l i c a t e t r i a l s were performed.

Aerobic Continuous Flow Reactors ,

Laboratory-scale, Plexiglas , act ivated sludge reac tors having volumes of 8.6 o r 8.0 l i t e r s were used i n t h i s study. and reciprocating) p is ton FMI and ( ro ta ry) p e r i s t a l t i c Cole Parmer pumps. Feed f o r each reactor w a s kept i n individual Nalgene containers. t o each reactor were checked d a i l y and adjusted as necessary. feed lines were per iodical ly removed, cleaned and replaced. through the laboratory 's compressed a i r system and passed through glass wool and a w a t e r t r a p p r i o r t o enter ing the reactors .

The reac tors w e r e fed by ( ro ta t ing

Flow r a t e s In addition,

A i r w a s provided

The reac tors w e r e run as complete-mix, no-recycle systems, so hydraulic Zetention t h e and mean c e l l residence time were equivalent. times consieered were 5 , 10, and 15 days, with residence times being varied by adjust ing inf luent flow r a t e . aera t ion

The detention

Complete-mix conditions were a t ta ined through

The feed solut ion t o each reactor consisted of r a w wastewater di luted t o provide a COD value of 2000 mg/L with d i s t i l l e d water. Phosphorus was added i n the form of a KK PO so lu t ion t o a t t a i n a EOD :P r a t i o of approximately 100:4. 2 4 5

To maintain a constant temperature the reactors were placed in a water f i l l e d aquarium and kept a t 25OC by aquarium heaters. s t a b i l i z e d a t 8.0 without adjustment. Dissolved oxygen (EO) in the reactors ranged from 6.0 t o 7.0 due t o the high r a t e of aerat ion necessary t o achieve good mixing. As a r e s u l t of t h i s high r a t e of aerat ion, it w a s necessary t o scrape the s ides of t h e reac tors da i ly t o re turn biomass t o the reactors . Plexiglas l i d s were placed over t he reac tors t o help prevent the loss of reac tor contents due t o evaporation.

The pH in a l l cases

Steady s t a t e conditions were assumed when ef f luent COD and suspended so l id s (SS) concentrations remained r e l a t ive ly constant f o r 7 t o 10 days. When steady s t a t e conditions were at ta ined, samples were co l lec ted for a period of 7 days. The analyses performed on ef f luents - from each reactor included ef f luent SS, soluble COD, TOC, TKX, NH3, NO3, NO-, 2 caprolactam, and t o t a l adenylates (ATP, ADP, and AMP) detenninatlons.

4

Organic Carbon and Ammonia Vo la t i l i za t ion Experiments

ammonia v o l a t i l i z a t i o n experiment was conducted t o determine how much nitrogen was removed from the reac tors by a i r s t r i pp ing and t o gain a b e t t e r understanding of the nitrogen balance i n the ac t iva ted sludge systems. The method used was a modified vers ion of t he technique described by Kissel e t a l . ( 8 ) . The apparatus consisted of a 2 0 c m Plexiglas cyl inder which was clamped t o a r ing stand and s l i g h t l y submerged i n t o the r eac to r contents. sample outside a i r was drawn through t h e cyl inder by m e a n s of a vacuum pump a t a rate of 1 4 cc/min over a one hour period. Air entered the cylinder j u s t above the water l i n e , ex i ted t h e cylinder about 7.6 c m from the top of the vessel , and then entered a gas scrubbing b o t t l e which contained 0.02 N H SO An impeller was mounted on top of t h e cylinder t o force aerosols created by aerat ion back t o t h e w a t e r surface, thereby preventing the droplets from entering the ammonia co l l ec t ion system.

-- For each

2 4‘

Organic carbon v o l a t i l i z a t i o n was a l s o examined t o see i f organic loading w a s being reduced due t o a i r s t r ipp ing . ident ica l t o t h a t used f o r ammonia with the exception of the trapping solution. Since the types of compounds possibly v o l a t i l i z i n g were unknown, four trapping so lu t ions were considered: d i s t i l l e d water a t pH 5, 6, and 9, and a 1:l mixture of methanol and water (11). The presence of v o l a t i l e organics w a s determined by TOC measurements.

The experimental procedure w a s

Amlyt ica l Procedures

Chemical oxygen demand (COD) was measured usir.g the dichromate re f lux method f o r 20 xi11 samples, as described i n Standard Methods ( 1 4 ) . In order t o obtain the soluble f r ac t ion of COD as w e l l a s t he soluble portion of the o ther parameters measured, samples were centrifuged a t 15,000 R P M f o r f i f t e e n minutes followed by f i l t r a t i o n through a 0.45 mu f i l t e r .

A D o h ” Envhotech t o t a l organic carbon (TOC) analyzer w a s used t o determine in f luen t and soluble e f f luen t TOC concentrations. Inf luent samples were d i lu ted with d i s t i l l e d water t o l eve l s c lose t o the carbon standards used f o r analyzer ca l ib ra t ion and e f f luen t concentrations.

I i

I Total Kjeldahl nitrogen (nW) was determined by the micro-Kjeldahl method I outl ined i n Standard Methods (14 ) . Samples w e r e digested using a gas heat ing

mantle and d i s t i l l a t i o n s were car r ied out on a Lahcon steam d i s t i l l a t i o n un i t .

concentrations i n both procedures w e r e determined using the titrimetric method. To obtain g rea t e r s e n s i t i v i t y f o r the lower ammonia concentraticns obtained i n the v o l a t i l i z a t i o n experiments, the phenolhypochlorite t es t described by Weatherburn (15) w a s employed. This is a colorimetric procedure whereby the two reagents, phenol plus sodium ni t roprusside and sodium hydroxide plus sodium hypochlorite, reac t with axanonia t o produce a pa le yellow color. Absorbance w a s measured on a Bausch and Lomb tometer (spectronic 20) a t 625 nm.

r Samples f o r amnonia ana lys i s only were a l s o d i s t i l l e d as above. Ammonia i

1

spectropho- E

l I .

i i ! <

I

5

The species , n i t r a t e and n i t r i t e , comprise what is re fer red t o a s t o t a l oxidized nitrogen, and are not included as p a r t of the TKN measurement. species were determined i n accordance with Standard Methods (14) I n i t r a t e by the brucine method and n i t r i t e by the azo-dye technique.

Both

Both raw and t r ea t ed wastewater w e r e exceedingly d i f f i c u l t t o f i l t e r even under a high vacuum with Whatman 40, fast f i l t e r i n g , f i l t e r paper. The presence of caprolactam polymers and co l lo ida l p a r t i c l e s were believed t o be responsible f o r this phenomenon. Because of t h i s poor f i l t e r a b i l i t y , SS levels could not be a t t a ined d i r ec t ly . dissolved so l id s w e r e obtained, with t h e d i f fe rence i n the two measurements yielding t h e SS concentration. Dissolved so l id s samples were obtained through centr i fugat ion and f i l t r a t i o n as described f o r soluble COD samples. continuous flow experiments 20 m l of sample w e r e used t o make these two so l id s determinations, while 10 m l samples w e r e used i n the batch experiments. measurements were made i n accordance with Standard Methods ( 1 4 ) .

Instead, t o t a l so l id s and t o t a l

For the

Both

Caprolactam concentrations were measured by gas chromatography using a H e w l e t t Packard Model 5880A coupled with an in tegra tor . were used f o r t he ana lys i s . 1240 DA, a polyester packing deact ivated f o r ac id i c compounds. i n j ec t ion po r t temperatures were set a t 1 7 O O C and 12OoC, respectively; and, the carrier gas flow w a s 30 cc/min. This column began breaking down, pro- ducing incons is ten t r e s u l t s and w a s replaced. packed with Alltech CS-8, a polar cyanopropyl s i l i cone packing. i n j ec t ion po r t temperatures w e r e set a t 25OoC and 22OoC, respectively; and the c a r r i e r gas flow was adjusted t o 40 cc/min.

Two d i f f e ren t columns

Oven and The f i r s t column w a s packed with 1 percent SP

The replacement column w a s Oven and

Dissolved oxygen (DO) and p H were regular ly checked i n each of the continuous flow reactors . A Fisher Accumet, Model 230, pH/ion meter and a Yellow Springs Instrument, Model 54A, dissolved oxygen meter were used t o make these measurements.

Adenosine tr iphosphate (ATP) and energy charge (EC) were obtained using 1 ml samples of MLSS and hea t deact ivat ing the sample f o r f i v e minutes i n 9 ml of bo i l ing T r i s buffer . This deact ivat ion s t e p ex t r ac t s the adenine nucleo- t i d e s from the cells, while simultaneously k i l l i n g the c e l l s and preventing fu r the r metabolic a c t i v i t y . v i a l and frozen u n t i l needed f o r analysis . and AMP t o ATP and t h e subsequent measurement of ATF' w a s described by Karl and Holm-Hansen ( 5 ) . An S A I , Model 2000, ATP Photometer, which provides a d i g i t a l readout of peak height was used i n making the ATP dete-&nations. Two-hundred mic ro l i t e r s of sample were p ipe t ted i n t o the photometer sample tube, and peak height was measured wit?i?iin 3 seconds. The use of a 0 t o 3 second peak height measurement i s preferred over longer periods because of i ts reproducibi l i ty and i t s capacity t o reduce in te r fe rence from non-adenine containing nucleotide tr iphosphates (5).

This so lu t ion w a s cooled, placed i n a s ter i le The procedure used t o convert ADP

f I

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Results

Batch Reactor Studies

Inhibi t ion curves were developed f o r both the raw wastewater and capro- lactam standard solut ions. u t i l i z a t i o n ra te versus e f f luent chemical oxygen demand (COD). Specif ic u t i l i z a t i o n r a t e (9) i s defined as follows:

These were establ ished by p lo t t i ng spec i f ic

ds/dt 9 = - X

where ,

ds/dt = change i n subs t ra te per u n i t time, mg/L/time x = MLSS, mgfi

The curves derived with caprolactam standards reproduced f a i r l y w e l l , although f igure 1 suggests t h a t t h e wastewater w a s somewhat more i n h i b i t 0 3 i n t r i a l 2 than i n t r i a l 1. and 0 t o 0.034 f o r t he f i r s t and second t r i a l s , respectively. u t i l i z a t i o n rates were obtained a t i n i t i a l COD concentrations of 257 and 260 mg/L. which the reac tors f a i l e d t o produce any reduction i n COD. this f a i l u r e occurred a t 211 i n i t i a l COD of 1940 mg/L, while an i n i t i a l COD of 1280 mg/L produced complete inh ib i t ion i n t h e second t r i a l .

The u t i l i z a t i o n r a t e s ranged from 0 t o 0,028 h r The m a x i "

The zero u t i l i z a t i o n rates correspond i n each case t o t h e point a t In the f i r s t t r i a l

The curves developed f o r t he r a w wastewater showed l i t t l e s imi l a r i t y , a s The u t i l i z a t i o n r a t e s f o r the f i r s t t r i a l ranged

, with the maxhnum r a t e occurring a t an i n i t i a l COD of can be seen i n f igu re 2 . from 0.03 t o 0.06 h r 1240 mg/L. wastewater l eve l s i n t h i s t r ia l . It can be seen, however, t h a t a reduction i n u t i l i z a t i o n rate d i d occur a t i n i t i a l COD conc n t r a t ions of 1200 t o 1400 mg/L; ye t , a r e l a t i v e l y high uptake r a t e of 0.04 h r i n i t i a l 1800 mg/L COD. The u t i l i z a t i n r a t e s of t he second t r i a l were g rea t ly reduced and ranged from 0 t o 0.04 h r (see f igure 2 ) . The maximum u t i l i z a t i o n rate corresponded t o an i n i t i a l COD of 208 mg/L. This curve also shows t h a t u t i l i z a t i o n r a t e s rap id ly decreased with increasing wastewater concentraticns (above 200 t o 300 mg/L COD) . Complete inh ib i t ion occurred a t an i n i t i a l COD of 787 mg/L.

-1

Mote that complete inh ib i t ion w a s not induced by increasing

-!? w a s s t i l l obtained a t an

-P

The difference be tweh t r i a l 1 and 2 r e s u l t s i n the batch s tudies w a s not readi ly apparent. More inhib i t ion w a s noted i n the second t r i a l s than the first t r ia ls of both the wastewater and pure caprolactum studies . the difference between the f i r s t and second t r i a l s with the wastewater w a s much more pronounced than the difference associated with the t w o caprolactam t r i a l s . The change i n u t i l i z a t i o n rates may, i n par t , have been due t o the physiological condition of t he biomass used i n the second t r ia l s . These t r i a l s were performed approximately f i v e months a f t e r t he f i r s t t r i a l s and organisms used i n the la te r t r ia ls were taken from the continuous flow

However,

7

0.09

0.035-

0.03s

1 0.02%

0.02

0.01

0.00

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Figure 1. Relationship of COD to specific utilization r h t e Of caprolactam; o = t r i a l 1, pre-continuous flow studies,

= trial 2, sost-continuous flow studies.

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i

Remaining COD, mg/L

8

0.05 4

0 . o o k

0 200 400 600 800 1000 1200 lUC0 1600 1800 2000

Remainin'g COD, mg/L

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Figure 2 . Relationship of COD t o spec i f i c u t i l i z a t i o n r a t e of wastewater components; = t r i a l 1, pre-continuous f l o w studies, 0 = t r i a l 2 , post-continuous flcw s tudies .

t

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r eac to r s of t h i s study. exposed t o the i n d u s t r i a l waste f o r a prolonged period and may have become more s e n s i t i v e t o t h e wastewater and caprolactan. This hypothesis does not f u l l y explain the pronounced d i f fe rence observed i n t h e wastewater t r i a l s , however. i n t h e wastewater during s torage and/or t he microbes were sens i t ized t o another component (o r components) i n the wastewater which w a s (or were) more i n h i b i t i o r y than caprolactam.

The microbes i n t h e second t r ia l s had therefore been

It may be t h a t some undetected transformation of components occurred

Another point of i n t e r e s t noted i n t r i a l s with both the wastewater and caprolactam standards w a s t h e presence of what appeared t o be a res idua l COD of 40 t o 50 mg/L. t h e batch s tud ie s typ ica l ly had an i n i t i a l COD of 50 t o 60 mg/L. During the course of an experiment t he COD of the f l u i d s i n cont ro l flasks which con- tained only sludge (i.e. no addi t iona l subs t ra te ) decreased t o about 40 t o 50

I n other words the f l u i d associated with the sludge used i n

W/L - Measurement of adenylate energy charge (EC) w a s a l so attempted throughout

t h e batch s tudies . L i t t l e va r i a t ion occurred i n the EC a t the various concen- t r a t i o n s of wastewater and caprolactam standards. 0.80 and 0.73 t o 0.76 f o r t h e wastewater and standard so lu t ions , respectively. Similar ly , ac tua l concentrations of ATP, ADP, and AMP remained r e l a t i v e l y constant i n a l l four t r i a l s . This lack of change i n what has been reported as a s e n s i t i v e t e s t w a s probably due t o the r e l a t i v e l y sho r t time period of t he batch experiments.

The EC ranged from 0.75 t o

Continuous Flow Experiments

Based on information derived from t h e i n i t i a l wastewater inh ib i t ion curve, an in f luen t COD concentration of 2000 mg/L w a s se lec ted for u s e during t h e continuous flow experiments. This 760 mg/L increase i n COD over t he concentration.(1240 mg/L COD) which yielded t h e maximum rate of u t i l i z a t i o n was used, because it w a s f e l t t h a t under continuous-flow conditions with a l a rge r MLSS concentration a s t ronger waste could be successfully t reated. In order t o obta in t h e 2000 mg/L of COD it w a s necessary t o make a 1:18 d i lu t ion of t h e r a w wastewater which resu l ted i n the following che rac t e r i s t i c s : t o t a l organic carbon (TOC) 635 mg/L, caprolactam 1102 mg/L, t o t a l Kjeldahl nitrogen (TfCN) 123 mg/L, ammonia 10 mg/L, and t o t a l oxidized nitrogen 0.07 mg/L. As mentioned e a r l i e r , chemostat reac tors operating a t ce l l residence times (Oc1 of 5, 10, and 1 5 days were used t o evaluate t h e b io logica l t r e a t a b i l i t y of t he wastewater.

Effluent carbon l e v e l s versus 0 . COD reductions achieved by the three reac tors a t 0- values of 5 , 10,'and 15 days were 988, 1789, and 1913 mg/L,

c; respect ively. 280, 545, and 581mg/L and 721, 1064, and 1100 mg/L, respect ively. The percent removals for these th ree systems from lowest t o highest B ' s were respec t ive ly 49, 89, and 96 percent f o r soluble COD, 44, 86, and G1 percent f o r so luble TOC, and 65, 96, and 100 percent f o r soluble caprolactam. removals a r e represented graphically i n f igu re 3.

The corresponding reductions i n TOC and caprolactam leve ls were

These

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1100-

10

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Figure 3. Soluble COD (n) , TOC (01, ar,d caprolactam (A) i n e f f luen t s from the continuous flow reactors .

l eve l s

I f.;

11

From the theo re t i ca l COD of caprolactam and t h e f a c t t h a t carbon accounts f o r 64 percent of t he compound's weight, 1 mg/L of caprolactam represents 1.86 mg/L COD and 0.64 mg/L TOC. lactam alone contributed t o e f f luen t COD and TOC l eve l s a t each Qc. it appears t h a t caprolactam read i ly underwent primary degradation, with i n t e r - mediates of biodegradation and o ther minor carbon containing compounds being responsible fo r a por t ion of t h e COD and TCC concentrations. A rapid f i r s t s t e p i n t h e biodegradation of caprolactam, followed by slower rate- l imit ing react ions, has been documented previously (3,9).

From f igu re 3, it i s c l e a r t h a t more than capro- However,

Nitrogen species versus 0 and e f f luen t carbon leve ls . Reduction in TXN w a s a primary concern of this s&dy, and the reac tors w e r e able t o decrease TKX leve ls -by 18, 50, and 65 mg/L a t O c a s of 5 , 10, and 15 day l eve l s , respec- t i v e l y . These decreases i n TXN correspond t o percent removals of 15, 41, and 53 percent. A corresponding increase i n NH concentration occurred as the organic nitrogen w a s mineralized. Increases i n the NH concentration were 46, 3 64, and 52 mg/L a t 5, 10, and 1 5 day 0 I s , respect ively. Figure 4 i l l u s t r a t e s the fa te of these two ni t rogen species a t t he v-zrious 0 ' s . From the graph it can be seen t h a t NH3 l eve l s a t oc's of 10 and 15 days exceeded TKN concentra- t i o n s somewhat. t heo re t i ca l ly not poss ib le and may have been due t o incomplete digest ion of samples i n the TKN ana lys i s o r shnpiy analytical e r rors . &partant point i s that a t 0,'s i n excess of 10 days, complete conversion of organic nitrogen t o amonia ni t rogen occurred. And, amnonih can, of course, be e f f i c i e n t l y removed by a i r s t r ipp ing , s e l ec t ive i c n adsorption, and nitrification-denitrification processes. contained i n the r a w wastewater, it might be economically f eas ib l e t o b io logica l ly convert t h e nitrogen t o anmonia and recover the ammoEia fo r use as a f e r t i l i z e r . so lu t ions , producing ammonium s a l t s such a s anrmonium s u l f a t e o r m.onium n i t r a t e .

3

C C

Since NH3 i s included i n the TKN measurement, this is

However, the

Given the quant i ty of nitrogen

This could be accomplished by capturing the NH3 i n acid

Only trace amounts of oxidized nitrogen w e r e detected i n the three reactors . have been shown t o be s e n s i t i v e t o caprolactam (13) and NH l eve l s i n 'Ihe reac tors were ra ther high.

Inh ib i t ion of n i t r i f i c a t i o n was expected s ince n i t r i f y i n g bac ter ia 3

Figures 5 and 6 i l l u s t r a t e t h e f a t e of NH and TXN as functions of e f f luen t TOC and caprolactam concentrations. por t iona l t o e f f luen t caprolactam and TCC concentrations, w h i l e ammonia l eve l s appeared t o equal TXN values and peak at caprolactam and TOC concentrztions of 38 and 90 mg/L, respec t ive ly . Thus, below 38 mg/L caprolactam or 90 q / L TOC nitrogen was in a form t h a t could readi ly be removed o r recovered.

4 f f luen t TXN l eve l s were pro-

Energy charge and ATP. Energy charge (EC) var ied l i t t l e , having the following values a t Ocas of 5, 10, and 15 days, respectively: Obsened concentrations of ATP were 0.03, 0.04, and 0.06 mg/L at 5, 10, and 15 days 0 I s , respect ively. small Eo suggest t ha t e i t h e r p a r m e t e r could be used a s a r e l i a b l e too l f o r assessing the stress ar,d/or eff ic iency of t h e b io logica l systems.

0.77, 0.76, and 0.73.

Tine changes Fn EC and ATP noted were therefore tco

9

1 2

2 6 0 10 12

O c t days

Figure 4. Fate of nitrogen i n the continuous a = N H 3 , 0 = TKN.

19 16

flow reac tors ;

13

1

1% 1

0 0 50

Effluent TOC, mg/L

figure 5 . Relationship of nitrogen t o e f f l u e n t organic carbon concentration; = NH3, 0 = TKN.

r L--

i

t c La r c r i

I L

i

Y

14

U 50 100 iso too 250 300 350 YDO

Effluent concentration, mg/L

Figure 6. Relationship of nitrogen t o e f f luen t caprolactam concentration: n = NH3, e = TKN.

15

Volatilization experiments. After the continuous flow studies had been completed, with the data revealing excellent transformation of organic nitrogen to ammonia nitrogen, volatilization experiments were conducted to gain information concerning nitrogen loss due to air stripping. A continuous flow reactor operating at a 20 day 0 The influent TKN loading on the reactor gas 41 mg/day, while soluble TKN effluent levels stabilized at 15 mg/day. The amount of ammonia recovered from this reactor was 13 mg/day. It therefore appears that approximately 30 percent of the influent TKN laoding was air stripped from the reactor in the form of NH

was used for these experiments.

3'

This reactor was also used to evaluate the possibility of organic loading being reduced due to volatilization. The influent TOC loading was 217 mg/day, with an effluent TOC of 22 mg/day. the reactor was a function of the trapping solution used. For distilled water at a pH of approximately 6 and distilled water adjusted to pH 5 and 9, the volatile TOC fractions detected were 7, 5, and 15 mg/day, respectively. The considerably larger amount trapped at the higher pH can be explained by the fact that the majority of the compounds in the proposed biodegradation pathway are acidic. trapping solution were highly variable and believed to be invalid due to the loss of methanol from the gas trap during the experiments.

The amount of volatile TOC recovered from

The results of the trials performed with the methanol/water

Evaluation of biokinetic constants. With data collected from the continuous flow studies, the values calculated for m a x i m u m rate of utilization (k), one-half the maxi" rate of utilization (Ks), growth yield (Y) , and m i roorganism decay (k ) were 2.5 d- , 1029.5 mg/L, 0.183 mg/mg, and 0.028 d domestic w stewater values for k, K Y and k are generally in the area of 2 to 10 d respectively. with errant predictions of system performance, when the calculated coefficients were used in the standard Lawrence and McCarty.mode1, prompted further evaluation of these numbers.

-f I respectively. MegcaPf and Eddy (10) report that in systems treating

-B d , 15 to 70 mg/L, 0.25 to'h.40 mg/mg and 0.04 to 0.075 d-l, The relatively low values obtained for k and Y in conjunction

In figure 7, the curve for effluent COD versus specific utilization rate was extended to intersect the x-axis. approximately at 40 mg/L of COD, which is believed to be the norhiodegradable fraction of the waste load. Note that this is consistent with the findings of the batch studies where a 40 to 50 mg/L residual was observed. After subtracting this residual from the steady-state effluent COD levels obtained in the three continuous flow experiments, the biokinetic constants were recalculated. , 223 mg/L, 0.173 mg/mg, and 0.03 d lower than those typically encountered. The coefficients, k and Y, are mostly likely low due to the inhibitory nature of the wastewater.

The point of intersection is

-1 The revis d values for k, K , Y and kd were 1.04 d -f , respectively. f'hese values for k and Y are again

Conclusions

- 1 I 1 I

i

i B

i

The conclusions derived from this study are as follows:

16

1.

0.

0.

0.

0.

0 100 200 300 1100 500 800 700 800 900 1000 1100

E f f l u e n t 'COD, m g / L

Figure 7. S p e c i f i c u t i l i z a t i o n rate as a f u n c t i o n of e f f l u e n t COD.

P

k I

17

1.

2 .

3.

4.

5.

1 1

1

Efficient conversion of organic nitrogen to ammonia nitrogen and removals of organic carbon were achieved at cell residence times greater than or equal to 10 days.

Caprolactam and the textile wastewater both exhibited inhibitory effects. This was demonstrated in the batch studies by decreased specific utilization rates at lower dilutions of the wastewater and by the low values of k and Y determined from continuous flow data.

Through both batch &d continuous flow studies, it appeared that there was a nonbiodegradable residual of 40 to 50 mg/L in a 1:18 dilution of the wastewater. , ,

The results of the batch experiments suggested that an inhibitory agent other than caprolactam was present in the wastewater.

Energy charge and ATP did not appear to be reliable indicators of suspended growth system performance and/or stress.

References

1.

2.

3 ,

4.

5.

6.

7.

a.

Anderson, G. A., Boardman, G. D., and Wallis, D. A., "Biological Treatability Study of Wastewater from a Nylon Fibers and Plastic Facility," Proceedings of the Annual Purdue Indcstrial Waste Conference, Purdue University (1983)

Fukumura, T., "Bacterial Breakdown of Caprolactam and Its Cyclic Oligomers," Plant and Cell Physiology, - 7, 93 (1967).

Fukumura, T., "Splitting of Caprolactam and Other Lactams by Bacteria," Plant and Cell Physiology, - 7, 105 (1966). Gvozdyak, P. I., Roi, A. A., Rotmistrov, M. N., "Sporogenic Bacteria, Active Destructors of Caprolactam," Prikl. Biokhh. Mikrobiol., 101, 5, 738 (1974), Chemical Abstracts, 81:175797q (1974).

K a r l , P. M., and Holm-Hansen, O., "Adenylate Energy Charge Measurements in Natural Seawater and Sediment Samples," ATP Methodolog-- Seminar, Vol. II., ed. by Borun, G. A., SA1 Technology Co., 141 (1977).

Kato, R. and Fukumura, T., "Bacterial Breakdown of Caprolactam," Chemistry and Industry, June (1962).

Kinoshita, S., Kobayashi, by Achromobacter guttatus 10,719 (1973).

E., and Okada, H., "Degradation of Caprolactam KF71," Journal of Fermentation Technology, 51

Kissel, D. E., Erewer, H. L., and Arkin, G. F., "Design and Test of a Field Sampler for Ammonia Volatilization," Journal of t\e American Soil Science Society, - 41, 1133 (1977).

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