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Plants in Constructed Wetlands Help to Treat Agricultural Processing Wastewater

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Plants in Constructed Wetlands Help to Treat Agricultural Processing Wastewater UC Agriculture & Natural Resources California Agriculture Title Plants in constructed wetlands help to treat agricultural processing wastewater Permalink https://escholarship.org/uc/item/67s9p4z8 Journal California Agriculture, 65(2) ISSN 0008-0845 Authors Grismer, Mark E Shepherd, Heather L Publication Date 2011 Peer reviewed eScholarship.org Powered by the California Digital Library University of California ReseaRch aRticle ▼ Plants in constructed wetlands help to treat agricultural processing wastewater by Mark E. Grismer and Heather L. Shepherd Over the past three decades, winer- ies in the western United States and sugarcane processing for ethanol in Central and South America have experienced problems related to the treatment and disposal of pro- cess wastewater. Both winery and sugarcane (molasses) wastewaters are characterized by large organic loadings that change seasonally and are detrimental to aquatic life. We examined the role of plants for treating these wastewaters in constructed wetlands. In the green- house, subsurface-flow flumes with agricultural processing wastewaters may have high concentrations of organic matter that volcanic rock substrates and plants contaminate surface waters when discharged downstream. at imagery estate Winery in Glen ellen, constructed wetlands with plants were tested for their ability to remove pollutants. steadily removed approximately 80% of organic-loading oxygen demand Shepherd et al. (2001) described the sugarcane and winery wastewater from sugarcane process wastewater negative impacts of winery wastewater Sugarcane, food-processing, winery after about 3 weeks of plant growth; downstream, which led to requirements and other distilleries generate waste- for its control and on-site treatment. waters from processing and equipment unplanted flumes removed about Similarly, downstream degradation wash-down. These differ greatly from 30% less. In field studies at two op- from sugarcane process waters has domestic wastewater because of their erational wineries, we evaluated the been documented in the Ipojuca River high organic-matter concentrations, performance of similar-sized, paired, of northeast Brazil (Gunkel et al. 2006) variable flow rates, relatively low levels and in coastal lagoons of northwest of nutrients, low pH and lack of patho- subsurface constructed wetlands with Mexico (González-Farias et al. 2006). gens. Gunkel et al. (2006) monitored and without plants; while both re- Wastewater from molasses processing sugarcane fertigation and wash-down moved most of the oxygen demand, follows a seasonal variation similar to waters (used to clean equipment) in removal rates in the planted system that of wineries, with high flows and Brazil and noted their very low pH (3.8) loadings from November through May, and high sodium (1,320 milligrams per were slightly greater and significantly followed by harvesting and grape crush liter), salinity and organic loads. Kumar different from those of the unplanted in late summer and early fall. et al. (2007) obtained similar results in system under field conditions. Both winery and molasses process India and also noted high sulfates. wastewaters are responsive to natural To determine the characteristics treatment strategies prior to discharge. of sugarcane process wastewater in he processing of sugarcane to cre- Remnant wetland systems, relatively Mexico, in March 2007 we compared Tate molasses for ethanol fuel and common in the drainage channels of wastewater from a typical processor, feedstock is rapidly expanding across Central and South America, may be Ingenio La Gloria, located on the coast Central and South America, while the employed. Likewise, constructed wet- south of Veracruz (Olguín et al. 2008), to number of vineyards and wineries con- lands have been designed and installed sugarcane process wastewater in India tinues to increase across the western to treat winery process wastewater and Brazil, and process wastewater United States. Both industries generate in California. Surprisingly, the role of from a California winery (table 1). In process wastewater (PWW) of variable plants and their associated biofilms in Mexico, sugarcane process wastewater quality, which can have deleterious im- such systems is poorly understood and is typically diluted 10 to 100 times with pacts on receiving surface waters when not well documented relative to treat- canal water prior to reuse for irriga- discharged downstream. ment performance. tion or release into drainage channels, http://californiaagriculture.ucanr.org • APRIL–JUNE 2011 73 making it similar in quality to that re- TABle 1. comparison of process wastewaters (PWW) from sugarcane in Mexico (ingenio la Gloria, ported for Brazil. The biological oxygen Veracruz), Brazil and india; and a california winery demand (BOD5, 5-day holding time) and chemical oxygen demand (COD) concentrations (both measures of or- Winery sugarcane (molasses) Brazil Brazil india Mexico ganic loading), and BOD5-to-COD ratio, Parameter* calif. PWW* fertigation† wash-down† PWW‡ PWW (± sD) for Brazilian sugarcane wastewater — . mg/L . as diluted for fertigation — were nearly Chemical oxygen 22,290 23,727 1,050 105,000 118,270 305 the same as that for the California demand (COD) winery process wastewater. While at Biological oxygen 14,490 10,800 388 52,500 52,200 200 much higher concentrations, the BOD5- demand (BOD5) to-COD ratio for the Indian sugarcane Total Kjendahl 1,598 106 process wastewater was similar. nitrogen (TKN) Shepherd et al. (2001) proposed that Nitrogen as ammonia 772 16 constructed wetlands are an attractive (N-NH3) treatment system for moderate-sized Nitrogen as nitrate 163 312 10 (N-NO ) wineries, with their ability to assimi- 3 Phosphorus as 67.7 2.2 1,100 45 late variable and large organic load- phosphate (P-PO4) (total) (total) ings as well as their low maintenance Sulfur as sulfate 61 6,250 8,220 197 and operational costs. Likewise, process (S-SO4) wastewaters can be treated naturally in Potassium (K) 19,250 250 drainage channels constructed at the Total solids (TS) 1,120 85,000 106,465 1,534 outflow of sugarcane processing facto- (TSS) ries. Such constructed wetlands make * Source: Shepherd, Grismer et al. 2001. † Source: Gunkel et al. 2006. use of wetland plants and associated ‡ Source: Kumar et al. 2007. microorganisms on the roots (called biofilms) to degrade organic pollutants such as carbohydrates, proteins and While plants are understood to be the relative value of planted versus un- other carbon-based suspended matter important to treating process waste- planted systems. that comprise the wastewater’s BOD water in constructed wetlands, little 5 constructed-wetland performance and COD load. quantitative information is available. Free-water surface ponds are one Biofilms are defined as spatially and The success of constructed wet- type of constructed wetland. In this sys- metabolically structured microbial lands in treating process wastewaters tem, vegetation is planted in base soils communities (Nikolaev and Plakunov containing high-strength organic mat- below water as deep as 4 feet. These 2007) that interact with plant roots ter depends on several factors related systems are easy to maintain and are and the soil-water environment, while primarily to organic loading, HRTs, acceptable for relatively modest organic constantly adapting to changes in the tolerance of selected plants to pos- loadings, but generally they are not both. As such, plant roots provide the sibly toxic components in the process appropriate for winery or sugarcane structure needed for biofilm bacteria to wastewater, and plant biofilm activity. processing unless the wastewater is process wastewater. Biofilm microor- Comprehensive research reviews of pretreated (such as in aerated ponds, for ganisms consume organic material and brewery, winery and related distillery odor and mosquito control). ultimately release carbon dioxide and treatment methods for process waste- Another type of constructed wet- water, or methane and water, depend- water have underscored the need for land, called subsurface-flow or veg- ing on the amount of oxygen present. additional research, particularly of full- etated submerged beds (fig. 1), involves Since the surface area of plant roots is scale systems and individual processes planting wetland vegetation directly far greater than that of the sand/gravel/ (Grismer and Shepherd 1998; Grismer into a gravel substrate 3 to 4 feet deep. rock substrate alone, and because roots et al. 1999, 2000, 2002, 2003). Shepherd, The wastewater passes through the have the ability to partially oxygenate Grismer et al. (2001) evaluated the per- gravel but does not cover its surface. their surfaces, they can support thicker formance of a subsurface-flow wetland This system has greater treatment capa- and perhaps more robust biofilms. In (20 feet long, 8 feet wide and 4 feet bility but also higher initial installation addition, plants consume some of the deep) in treating winery process waste- costs. process wastewater nutrients, while water flows ranging from 80 to 170 Rates of flow into such constructed roots physically filter them. In some cubic meters per day at organic loads of wetlands are managed so that there cases the aesthetic appearance of the 600 to 45,000 milligrams COD per liter is sufficient hydraulic residence time constructed wetland is not a concern, (mg COD/l), and measured average re- (HRT) for adequate treatment. COD or but the processing plant operators may moval rates of 98% for COD and 97%
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