Title:

Contract No.

Institution:

Date:

Contract Date:

Anticipated Completion Date;

Government Award:

Project Director:

Project Manager:

PIS:

Technical Project Officer (COR):

Reporting Period:

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OUARTERLY TECHNICAL REPORT:

WETLAND TREATMENT OF OIL AND GAS WEL-- L WASTEWATERS

DE-AC22-92MT92010

University of Michigan, Department of Chemical Engineering

October 4, 1993

May 25,1992

May 24,1994.

( $89,560 for the Second Year )

Prof. Robert H. Kadlec

Dr. Keeran R. Srinivasan

Prof. Robert H. Kadlec and Dr. Keeran R. Srinivasan

Dr. Brent W. Smith

May 25,199$- 'Aug. 24,1993. 9

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Executive Summary:

During the first quarter of the above contract, all the elements of Task 1 were completed. The first quarterly report (1) presented an overview of a wetland and its increasing use in industrial waste water treatment. An idealized, reaction engineering description of wetlands was presented to demonstrate how the various processes that occur in a wetland can be modeled. Previous work on the use of wetlands to remove BOD, TSS, Phosphorus and Nitrogen was reviewed. Recent literature on the application of wetland technology to the treatment of petroleum-related waste water was critically evaluated and an outline of the research plans for the first year was delineated. Further, our literature search (nominally completed under Task 1) unearthed more recent studies (some unpublished) and a summary was included in the second quarterly report (2). In the second quarterly report, results of our efforts on the construction of a laboratory-type wetland were also reported. Initial studies on the use of wetland amendments such as modified- clays and algae cells were presented and discussed (2). In the third quarterly report (3), adsorption of heavy metals ions such as Cu(II) and Cr(VI) onto soils drawn from the laboratory- type wetland was shown to be weak. Secondly, it was shown that modified-clays did adsorb Cr(vI) ions strongly at pH 4.5. Further, studies on the pH dependence of the adsorption of p- naphthoic acid, (NA), a well-documented contaminant in many oil and gas well waste waters (4), onto modified-clays were undertaken and it was shown that uptake of NA by modified-clays was of the high affinity type at pH 4.5 and 7.0, but weak at pH 9.0. Adsorption of heavy metal ions, Cu2+, and Cr(V1) onto algae, a proposed wetland amendment, was carried out and the results were presented and discussed in the fourth quarterly report (5). Uptake of NA by the soil component of the laboratory-type wetland was monitored as a function of pH. The adsorption of NA onto modified-clays was studied in greater detail and these data were described and analyzed in the previous quarterly report (5).

The dynamics of the uptake of phenol and P-naphthoic acid by laboratory-type wetland systems have been studied and the results are presented and discussed.

II. Task 3A: Dynamics of the Uptake of Toxic Organics by Laboratory-type Wetlands.

In a previous report (2), we had described the design and the construction of a laboratory-type wetland. Briefly, 18-gallon plastic containers containing 4 cattails/container were prepared in a suitable soil matrix and grown at the Botanical Gardens operated by The University of Michigan.

Uptake experiments were conducted in the following manner:

(1)

(2)

Removed the overlying water and replaced with fresh tap water.

After 24 -hr equilibration, determined the height of the water column and spiked the overlying water with phenol or p-naphthoic acid to a pre-determined concentration, Following the addition of the toxic organic, the water was mixed manually with a paddle, and was left undisturbed thereafter.

(3) Collected water samples prior to the start of the experiment and periodically during the experiment. The temperature and the pH were noted.

The concentration of phenol in the supernatant water was determined spectrophotometrically following steam distillation of the water sample (6). On the other hand, P-naphthoic acid was

DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

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assayed fluorimetrically after filtering the sample and the standards through a 0.22 ym filter using the standard addition method. Details are given in Table I.

Table 1: Assay of Phenol and B-naphthoic acid:

Phenol Adsomtion on Microcosm:

Initial Concentration:

Sample Size:

Analysis Method:

Temp.

PH

&Naphthoic Acid Sorption:

Initial Concentration:

Sample Size:

Analysis:

Temp. and p H

100 PPm

50 ml

Steam Distillation and W Absorbance

@ 268 nm

Room Temp.

7.5 - 8.5

10 PPm

20 ml

Filter through 0.2 pm Membrane,

Fluorescence detection using the Standard

Addition method with two standard spikes.

of 1.0 and 2.5 ppm

Ex. 287 nm

Em. 360 nm

Room Temp. and 7.5 respectively.

A preliminary sorption experiment was conducted on a single wetland, and based on the data obtained phenol and P-naphthoic acid uptake were canied out respectively on a separate set of 2 and 3 wetlands each. Similar experiments to determine the potential evaporative losses of phenol were also undertaken. The combined results of phenol uptake by the wetlands and its evaporative losses are shown in Figs 1 - 4. In Fig. 5, the results of P-naphthoic acid adsorption are displayed.

\

E

3

Fig. 1 Phenol Calibration Curve 60

50

3 40 a a W

20

10

0 0.0 0.1 0.2 0.3

Absorbance 268 nm 0.4

Fig. 2 Comparison of Phenol Assay before and after Stearn Distillation

100

80

r?

60 a 0

W w

40

20

0

y = -0.145 + 158.8*~; RA2 = 1.000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 Absorbance 268 nm

i

120

100

80

60

40

20

0

4

Fig. 3 Uptake of Phenol by Laboratory-type Wetlands y = 103.8 - 1.43*~ RA2 = 0.96

' 9 1 I I I

0

130

120 - a &lo W

90

80 0

10 20 30 Time (hours)

40 50

Fig. 4 Rate of Evaporation of Phenol

f 0 # 5 8 17 # 4 5

10 20 30 Time (hours)

40 50

. . 5

Fig. 5 Uptake of 2-Naphthoic Acid by Laboratory-type Wetlands

I

loss of phenol by evaporation was measured and is shown in Fig. 4. It is clear that evaporative

0 100 200 300 Time (hours)

Phenol UDtake;

Fig. 1 is a calibration curve for the assay of phenol using the UV absorbance method. Concentrations as low as 5 ppm could be determined with very little uncertainty. Even though the water samples had a slight coloration, UV absorbance method following steam distillation was found to be quite effective and reproducible. The validity of this approach is verified in Fig. 2. Phenol standards were spiked into water drawn from one of the wetlands (not used in the uptake measurements) and the phenol assay was performed following steam distillation of the water samples. The amount of phenol recovered was compared with the amount initially added. The recovery was close to 100%. Secondly, the calibration line was identical to the one obtained with phenol standards ( compare the linear calibration equations shown in Figs 1 and 2).

Phenol uptake by laboratory-type wetlands is quite rapid, and appears to be linear with respect to time. The results shown in Fig. 3 indicate that, although a linear fit of the data has an acceptable correlation coefficient, the disappearance of phenol is most likely mediated by a number of processes such as biodegradation, simple sorption, and evaporation. Each data point shown in Fig. 3 is an average of two measurements at each time period and the two lines represent fits to the data obtained from two different wetlands. Both the wetlands show similar behavior.

The potential loss of phenol through evaporation was examined using surface evaporation method. The tap water used in the uptake experiments (described above) were spiked with phenol and allowed to evaporate from a container of nearly identical surface area. The rate of

losses of phenol are substantial. However, the extent of evaporative loss is much lower than the degree of removal of phenol by the wetlands examined in this study. It appears, therefore, that evaporative losses can not account for the full extent of phenol removal by a typical wetland. The data show oscillatory behavior (Fig. 4), and in order to explain this phenomenon, temperature and the pH of the overlying water were recorded during wetland and evaporation experiments. It was observed that variations in temperature and pH were small and similar in both cases. It is worth noting that a downward turn in phenol concentration with time is discernible in Fig. 4 despite random fluctuations in some of the raw data.

D-naDhthoic ac id somt ion;

The disappearance of 2-naphthoic acid (NA) from the supernatant water was much slower than phenol uptake. The results are shown in Fig. 5. Even after 12 days the loss of NA from the supernatant was only around 50%. The temperature and pH were nearly the same as in the phenol uptake experiments. The combined use of filtration and the standard addition method enabled us to quantify NA concentrations with a high level of reproducibility. The fact that the disappearance of NA is a much slower process would indicate that a loss mechanism such as evaporation may be unimportant. Sorption to various components of the wetland appears to be a main removal mechanism. It is however possible that adsorption of NA to different components of the wetland is not of the high affinity type. Biodegradation can not be ruled out because naphthalene and substituted naphthalenes are known to be biodegraded rapidly and easily.

Assuming sorption is the most likely removal mechanism, the pH of the overlying may not have been optimum to promote strong adsorption. A lower value of pH might have been more effective. Further work is in progress . III. Future Work:

Based on the results described above, uptake of P-naphthoic acid, phenol by laboratory-type wetlands will be studied in greater detail. Similar studies on uptake of heavy metals by laboratory-type wetland have been started. Furthermore, a large number of the laboratory-type wetlands have been supplemented by the addition of peat from an operating wetland in Michigan, and the effectiveness of the peat in promoting uptake of toxic organics and heavy metals will be considered.

IV: SUMMARY

This quarterly report presents results from studies on the uptake of phenol and P-naphthoic acid by laboratory-type wetlands designed and built during the earlier phases of this study. The uptake of phenol by the wetlands is quite rapid, and nearly complete in 50 hours, but it was also found that evaporative losses of phenol from the supernatant water during the same time period was considerable. On the other hand, P-naphthoic acid (NA) is sorbed quite slowly and there was no indication of evaporative losses in the case on NA.

V: Report Distribution List:

Document Control Center U. S. Depamnent of Energy Pittsburgh Energy Technology Center P. 0. BOX 10940, MS 921-1 18 Pittsburgh, PA 15236-0940.

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REFEREP

7

CES:

R. H. Kadlec and Keeran R. Srinivasan: 1st Quarterly Report, U. S. DOE, PETC, August, 1992. R. H. Kadlec and Keeran R. Srinivasan: 2nd Quarterly Report, U. S. DOE, PETC, November, 1992. R. H. Kadlec and Keeran R. Srinivasan: 3rd Quarterly Report, U. S. DOE, PETC, March, 1993. J. R. Gulley and P. G . Nix: 'I Wetland Treatment of Oil sands Operation Waste water I' ( A private Communication from authors to R. H. Kadlec, PI). R. H. Kadlec and Keeran R. Srinivasan: 3rd Quarterly Report, U. S. DOE, PETC, July, 1993. Standard Methods for the Examination of Water and Wastewater: 16th Edition, Prepared Jointly by MHA, AWWA, amd WPCF, (Publ.) American Public Health Association. Washington, D. C., pp 556 ( 1985).

Publications: None