Treatment of potato processing wastewater with engineered natural systems

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Wat. Sci. Tech. Vol. 40. No.3. pp. 211-215. 1999

Pergamon

IC 19991AWQ Published by Elsevier Science Ltd

Pnnted in Great Britain, All rightsreserved 0273-1223/99 $20.00 + 0.00

PH: S0273-1223(99)00412-6

TREATMENT OF POTATO PROCESSING WASTEWATER WITH ENGINEERED NATURAL SYSTEMS Peter S. Burgoon*, Robert Ii. Kadlec** and Mike Henderson*** ·Water Quality Associates. Inc. 103 Palouse Street, Suite #2, Wenatchee, WA 98801. USA ··Wetland Management Services , 6995 West Bourne, Chelsea, MI488118, USA ···Lamb Weston, Inc. 2005 Saint Street, Richland, WA 99352, USA

ABSTRACT A full-scale integrated natural system has been used to treat high strength potato processing water for 2 years. The integrated natural system consists of free water surface and vertical flow wetlands, and a facultative storage lagoon. Influent wastewater averages 2800 mgIL COD, 150 mgIL TN and 350 mgIL TSS . Approximately 5300 m1/d of wastewater flows through the treatment system annually. The treatment objective is a 53% reduction in total nitrogen. The wastewater application permit requires an annual nitrogen load of 500 kglha yr on 213 hectares orland used to grow alfalfa and other fodder crops. Free water surface wetlands are used for sedimentation, mineralization of organic matter, and denitrification. Vertical flow wetlands oxidize organic matter and nitrogen . A lagoon provides storage during the winter when irrigation is not possible and functions as a facultat ive lagoon . Free water surface wetlands were planted with Typha latifolia and Scirpus validus in fall 1995. Wastewater application began in July of 1996. In the summer months COD removal has been greater than 95% through the free water surface wetlands and vertical flow wetlands . The removal rate decreased to about 75% in the winter. Average summer water temperatures are 18°C; average winter water tempe ratures are )OC. Ammonia removal through the vertical flow wetlands averages 85% during the summer and )0·50% removal during the winter. Addition of exogenous carbon to the free water surface wetlands resulted in 95% removal of N03-N. Use of natural systems have proved to be a cost effective treatment alternative for high strength industrial wastewater. (\:I 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved

KEYWORDS Constructed wetlands; potato processing wastewater; nitrogen removal; vertical flow wetlands; surface flow wetlands.

INTRODUCTION Kadlec et al. (1997) reviewed the use of pilot-scale wetlands for treatment of potato processing wastewater in Washington and Oregon. The pilot -scale work provided the basis for design and construction of a fullscale treatment facility owned and operated by Lamb Weston, Inc, in Connell, Washington. Connell is located in central Washington in the Columbia Basin. The basin is an arid agricultural area sustained by irrigation water from the Columbia River. The arid region receives approximately 20 ern (8 in) of rain and about 50 em (20 in) of snow per year. 211

P. S. BURGOON eta/.

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Description of Facility. Wetland components were designed for sequential treatment of the wastewater. Wastewater is pumped from a primary clarifier to ten hectares of free water surface wetlands constructed for sedimentation and mineralization of wastewater (WIIW2). The process water from the WIIW2 wetlands is sprayed onto 4 hectares of vertical flow wetland (W3) for oxidation of carbon and nitrogen. Water flows by gravity from the W3s into 2 hectares of denitrifying free water surface wetlands (W4). Raw process water is supplemented to augment denitrification in the wetlands. Treated process water flows into a 0.48 million-nr' lagoon (126 million-gallon) that provides facultative treatment and storage prior to land application. The wetlands were constructed in stages throughout 1994 and 1995. Construction and planting of the wetlands were completed in fall 1995. All wetlands were lined with 1.0 mm (40 mil) HDPE liner impregnated with carbon black for UV resistance. All free water surface wetlands had 20-30 em (8-12 inches) of native soil placed on the liners as soil for Typha sp. and 2 species of Scirpus sp. Plants were established in irrigation water for 8 months prior to application of process water. The vertical flow wetlands were filled with 0.9 metre of a local sand (Dso = 2.6 mm) excavated on site. The vertical flow wetlands were operated as intermittent sand filters with duty cycles of 6 to 72 hours. They have not been planted with Phragmites australis due to poor growth when sprayed with the wastewater (Kadlec et al. 1997). Table 1. Surrm1rv of water aualitv for treatm:nt s''StemfranAailI997 - April 1998 I SlITIret' ~ (A lIil- October) Wmter ~ - 98(NoveniJer - March) Influent WI12 W3 W4 Storage % Influent WI12 W3 W4 Storage I % m31d T,oC COD TSS 'IN IOmN NH4-N N03-N InH

31 2218 329 1.54 59 93 2 6.4

5643 13 262

65 138 15 121 1 7.7

16 144 39 130 29 47 54 7.0

14 175 45 90 19 .54 17 7.5

16 175 46 89

15 63 11 8.0

92 86

42 75 33

33 2838 324 176 62 113

1 5.9

4035 4

5

6

346 200 TTl 33 25 41 133 96 71

18 28 21 115 42 45 1 26 5 7.4 6.9 7.1

5 159 65 60 10

45 5 7.3

94 80 66

84 60

The wetlands system is designed to treat an annual flow of 1.4 mgd of wastewater with annual average concentrations of 3150 mgIL COD, 575 rng/l TSS, 149 mgIL TKN, and 30 mgIL ~-N. The winter design temperature was 1°C. The design goal was minimal odors and 53% removal of total nitrogen. After nitrogen removal is achieved the water is applied to 213 hectares (525 acres) of fodder crops. Water depths in the wetlands during the summer and winter were 30 and 45 ern respectively. The deeper water allows adequate flow through the wetlands during freezing conditions. The thickest ice measured was about 6 ern during the winter of97-98. Average water temperatures during the coldest part of the year were about 1.5 "C, Average air temperatures were below freezing for several consecutive weeks. Sample collection and analysis. Samples were collected 3 times per week at the effluent of each treatment component and analyzed on site within a couple hours. Chemical oxygen demand, TN, and N03-N were analyzed with Hach colorimetric test kits. The NH4-N was measured using a Hach ion specific electrode (Hach Company 1997). OPERATIONAL RESULTS AND DISCUSSION Water quality A summary of operational data shown in Table I is from April 1997 to April 1998. The data is generalized into summer and winter operations. This table excludes data from the first winter (96-97) because concentrations were unusually high due to start up. Therefore, the table shows what should be expected from an established wetland treatment system. Data for COD and TN from "start up" are shown in Figures 1 and 2.

Treatment of potato processing wastewater

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COD removal. The net COD removal through the system is greater than 90% all year round. The Wl/W2 wetlands removed about 85-90% of the COD, and 80-90% of the TSS. The removal of COD decreased in the coldest winter months. Figure I shows that effluent COD decreased as influent COD decreased. The higher effluent concentrations may also have been due to "start up"and establishment of the anaerobic bacteria. The COD was low in January 98 due to recycling of storage lagoon water through the wetlands while the processing plant was not processing potatoes. During 1998 COD concentrations have consistently averaged <500 mg/L in the winter and <300 mg/L in the spring and summer. The high rate of COD removal facilitates nitrogen oxidation in the W3s and reduces the odors during spray irrigation. The elevated COD from the W4 wetlands is due to addition of raw water for denitrification. Denitrification during summer 1997 was poor (Table 1) due to poor plant establishment, poor control of raw water loads, and pulsing of N03-N to the W4 wetlands. Poor establishment of cattails and bulrush appeared to create areas for hydraulic short-circuiting and reduced plant biomass for denitrifying bacteria. Since the majority of conditions contributing to reduced denitrification rates have been resolved >90% denitrification may be achieved with an excess of25 -75 mgIL COD in the W4 effluent.

Figure 1. Average montbly COD from tbe Wl/2 wetlands 4500 4000

- - Io n uent

....... WI/W2 ernuent

3 500 3000 ,.l

~

E 2500

C 2000 0

u

1500 1000 50 0

The averafe COD loading to the Wl/W2 wetlands was 0.5 kg/nr'd (31 Ib/IOOO ft3 d) and 0.3 kg/m'd (18 Ib/l000 ft d) for the summer and winter respectively. This loading rate is similar to low rate covered anaerobic lagoons used for COD reduction in food processing (Malina and Pohland 1992, Cocci et al. 1997). The effluent concentrations from the wetlands are lower in COD and TSS than from equivalently loaded covered anaerobic lagoons (Cocci et al. 1997). TSS removal. The effluent TSS from the WI/W2 wetlands is consistently less than 75 mg/L. As the wetland plants and litter layer matures the TSS concentrations have decreased, consequently winter 97-98 concentrations are lower than summer 97. The WI/W2 wetland plants and litter have proven to be very effective in solids removal. The TSS concentration in the W4s was higher than expected due to die off of large areas of an annual plant that became established before the wetland plants. The wetland plants have since become well established and are expected to improve performance. The TSS increases in the lagoon due to algal growth.

Nitrogen removal Total nitrogen. TN removal gradually deteriorated after start up; by May 97 the monthly average removal was only 12% (Figure 2). In Table 1 TN removal appears higher in the winter due to the deterioration in performance. Wastewater was not infiltrating the W3s and resulted in surface flow and minimal treatment. When treatment problems were remedied TN removal was greater than 70% by September 1997(Figure 2).

214

P. S. BURGOON et al.

Good performance was sustained through the winter of 1997 and 1998 verifying resolution of earlier problems. The results are that the wetlands are operating better than design expectations. Figure 2. TN removal in tbe engineered natural system 250 . . . , . . . . . - - - - - - - - - - - - - - - - - - - - - - - - - - - . ..... Innunt TN

200

..... WllWl

...... W3

...-W4

t------r------::;;-.~;;;;""'""\_---------_=_-____==______i

50 + - - - - - - - - - - - - - - - ' = . t - - - ; ; I I " - I - - - - - - - - - - - - i

Annual TN removal must be greater than 53% for all the wastewater to be land applied at the permitted annual rate. Table 2 shows the permit limit and system performance for the first (96-97) and second (97-98) permit years (November to November). During the first application year total nitrogen applied to the field was 12% less than permitted for the fields, despite the poor TN removal during "start up". As of March 1998, less than 30% of the TN applied by March 97 has been or is available to be applied to the fields (Table 2). TN application to the fields is expected to be significantly below the treatment goal due to improved operations of the W3s and W4s. Table 2. Total nitrogen in storage and applied to fodder crops with land application. TN annual load permitted to fields TN applied from November 1996 to November 1997 TN applied from November 1996 to March 1997 TN applied from November 1997 to March 1998

TN,kg 131,100 116,000 92,140 26,400

Organic nitrogen. The potato water mineralizes very rapidly so that >60% of the organic nitrogen was mineralized to NH4-N prior to entering the wetlands (Table I). This mineralization continued in the WIIW2 wetlands so that 7.0 and may have contributed to volatilization of Nlh-N, The majority of the ~-N removal occurred in the W3s. Periodic adsorption of ~-N appears significant and may account for some ~-N removal that is assumed to be nitrification. Evidence that adsorption was an active mechanism for N retention was the high N03-N concentration (highest recorded was 300 mgIL) that was flushed from the W3s after several days of down time. After remediation of the W3s performance improved markedly; average influent and effiuent ~-N concentrations for February-April 1997 werel62 and 131 mgIL respectively; the same months in 1998 had average influent and effluent concentrations of 131 and 47 mg/L NH4-N respectively. Duty cycle ranged from 6 to 72 hours; cycles from 6 to 48 hours did not appear to affect nitrification rates. Nitrification was reduced in the winter but was significantly higher than expected for operational water temperatures less than 4°C. During all except the coldest months of the year the water is warmed I-2°C after

Treatment of potato processing wastewater

21S

passage through the W3s. During extended periods with daytime temperature below freezing, the W3s were bypassed due to thick layers of ice on the wetland surfaces. ~N removal rates averaged 11.6 glm 3 d and 8.2 g/rrr' d during summer and winter respectively. Nitrate and nitrite removal. Nitrate removal is critical for compliance with TN removal goals and to minimize the amount of oxidized N that is land applied. Denitrification may have occurred in the W3 wetlands. Although W3 effiuent water always had 1-3 mg/L D.O., nitrogen balances implied denitrification or ~-N adsorption in the sand. The majority of the denitrification occurred in the W4 wetlands. There was not sufficient endogenous carbon in the W4 wetland to support significant denitrification. Addition of raw potato water allows >90% denitrification but also resulted in increased effiuent ~-N concentrations. Approximately 5-7 N03-N were removed for each ~-N added. As operations and plant litter become better established the removal ratio improves.

During start up this system produced strong odors as the biological ecosystem transitioned from aerobic (with clean irrigation water) to anaerobic (full strength process water). The strongest odors were produced when large populations of purple sulfur bacteria in the WlfW2 wetlands died and resulted in sulfides >40 mg/L. These "start up"odors may be avoided if wetland plants are well established prior to wastewater application, and start up begins in early summer. Since the wetland treatment system has stabilized odors are not a problem. Some odors are present at the influent wetland cells (about 10% of the WlfW2 wetlands). These odors are most likely due to volatile fatty acids and sulfur compounds. The remainder of the treatment system has no significant odors. The final product is high quality water with available nutrients and no odor problem during land application. Operations and maintenance This full-scale system is pioneering the use of engineered natural systems for treatment of high strength industrial wastewater. The intensive sampling and analysis for the past two years (3-5 times per week) and engineering modifications have required two full-time personnel. CONCLUSIONS The WlfW2 wetlands perform as effective pretreatment units for nitrification. The COD and TSS removal from the WlfW2 wetlands is equal to or better than similarly loaded covered anaerobic lagoons. The vertical flow wetlands are very effective in removing nitrogen throughout the summer and winter. Winter rates are higher than expected for the cold temperatures. The engineered natural systems produce an odor free, low nitrogen wastewater for use in land application and production of fodder crops. Continued research and development in operations and design of the full-scale system has resulted in performance better than the original design. ACKNOWLEDGEMENTS Key members of the team have been Tom Hockett, Frank Kirkbride, and Chris Aldrich. The success of this and many wetlands in the Northwestern U. S. is due to the vision and hard work of Rex van Wormer, who passed away on May 13, 1998. REFERENCES Cocci, A. A., Page, I. C., Grant, S. R. and Landine, R. C. (1997). Low-rate anaerobic treatment of high-strength industrial wastewater: ADI-BVF case histories. Presented at the Anaerobic Treatment for Industrial Wastes Seminar. East Syracuse, New York. Hach Company. (1997). Catalog ofProducts for Analysis. Available from Hach Company, P. O. Box 608, Loveland, Colorado, USA 80539-0608. Kadlec. R. H., Burgoon. P. S. and Henderson. M. E. (1997). Integrated Natural Systems for Treating Potato Processing Wastewater. Water Sci. Techn. 35(5),263-270. Malina, 1. F. and Pohland, F. G. (1992). Design ofAnaerobic Processes for the Treatment of Industrial and Municipal Wastes. Technomic Publishing Company, Inc. Lancaster, PA.