Maximizing total nitrogen removal from onsite-generated wastewater.Background Conventional wastewater treatment Conventional wastewater treatment
ni·tri·fi·ca·tion n. 1. of organic nitrogen and ammonia (total Kjeldahl nitrogen Total Kjeldahl Nitrogen or TKN is the sum of organic nitrogen; ammonia, NH3 and ammonium, NH4+ in biological wastewater treatment. TKN is determined in the same manner as organic nitrogen, except that the ammonia is not driven off before the [TKN TKN Total Kjeldahl Nitrogen TKN Takanini (suburb of Auckland, New Zealand) ]) to nitrate and the denitrification de·ni·tri·fy tr.v. de·ni·tri·fied, de·ni·tri·fy·ing, de·ni·tri·fies 1. To remove nitrogen or nitrogen groups from (a compound). 2. of nitrate to nitrogen gas have received much attention from the regulatory community. This attention is especially marked for onsite-generated wastewater because of an increase in population densities in areas without sewers and in environmentally sensitive regions. The U.S. Environmental Protection Agency Environmental Protection Agency (EPA), independent agency of the U.S. government, with headquarters in Washington, D.C. It was established in 1970 to reduce and control air and water pollution, noise pollution, and radiation and to ensure the safe handling and (U.S. EPA EPA eicosapentaenoic acid. EPA abbr. eicosapentaenoic acid EPA, n.pr See acid, eicosapentaenoic. EPA, n. ) recognizes the permanence and importance of onsite wastewater treatment. Therefore, new processes that can more comprehensively treat wastewater, including the removal of nutrients and optimization of existing technologies, are being developed (U.S. EPA, 2000). In a conventional wastewater treatment system, BO[D.sub.5] provides a soluble substrate for microorganism microorganism /mi·cro·or·gan·ism/ (-or´gah-nizm) a microscopic organism; those of medical interest include bacteria, fungi, and protozoa. growth resulting in the production of water and carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. . Nitrogen is required for growth and originates from the wastewater. With the removal of excess cells from the secondary clarifier, nitrogen contained within the removed cells exits the process. Because the nitrogen that had been incorporated in the removed cells is far less than that present in the wastewater, strict standards for effluent nitrogen levels cannot be reached simply by removal of BO[D.sub.5] and the associated excess cells from the system. Furthermore, excess cells are seldom discarded from onsite wastewater treatment as these processes operate as an extended aeration aeration /aer·a·tion/ (ar-a´shun) 1. the exchange of carbon dioxide for oxygen by the blood in the lungs. 2. the charging of a liquid with air or gas. aer·a·tion n. basin. In these systems, newly formed cells are allowed to oxidize oxidize /ox·i·dize/ (ok´si-diz) to cause to combine with oxygen or to remove hydrogen. ox·i·dize v. 1. To combine with oxygen; change into an oxide. 2. to carbon dioxide and water, resulting in the release of nitrogen back into the water. To achieve BO[D.sub.5] reduction and substantial removal of nitrogen (comprehensive wastewater treatment) to below the levels required for cell growth, multiple microbiological populations and environments are required: * BO[D.sub.5] oxidation to carbon dioxide and water requires a heterotrophic heterotrophic /het·ero·tro·phic/ (-tro´fik) not self-sustaining; said of microorganisms requiring a reduced form of carbon for energy and synthesis. population and aerobic conditions. * Nitrification of organic nitrogen and ammonia to nitrate requires an autotrophic autotrophic /au·to·tro·phic/ (aw?to-tro´fik) self-nourishing; able to build organic constituents from carbon dioxide and inorganic salts. population and aerobic conditions. Before substantial nitrification occurs, the BO[D.sub.5] must be substantially depleted de·plete tr.v. de·plet·ed, de·plet·ing, de·pletes To decrease the fullness of; use up or empty out. [Latin d . * Denitrification of nitrate to nitrogen gas requires a heterotrophic population and anoxic an·ox·i·a n. 1. Absence of oxygen. 2. A pathological deficiency of oxygen, especially hypoxia. [an- + ox(o)- + -ia1. conditions. Denitrifiers require an easily degradable de·grad·a·ble adj. That can be chemically degraded: degradable plastic wastes. de·grad carbon source. To achieve multiple populations and oxidation/reduction environments multiple tanks are often used. Several examples are described by Metcalf and Eddy (2003, pp. 741-746). When sequential tanks are used for BO[D.sub.5] oxidation/nitrification and denitrification, carbon for denitrification must be added because the BO[D.sub.5] (a very good source of easily degradable carbon) has largely been depleted once the wastewater reaches the denitrification tank. There are several options for providing carbon for denitrification. Nitrate-rich effluent can be recirculated to the front of the plant, mixed with the influent in·flu·ent adj. Flowing in or into. n. 1. An inflow, especially a tributary. 2. Ecology A nondominant organism in a community that exerts an important modifying effect. water that is high in BO[D.sub.5], and then treated in an anoxic reactor (the first treatment unit). Alternatively, influent wastewater (high in BOD BOD: see sewerage. ) can be metered to and mixed with nitrate-rich effluent and then proceed into an anoxic reactor (the last treatment unit). Instead of the influent BO[D.sub.5] being used for carbon, an external source such as methanol can be mixed with the secondary effluent and treated in an anoxic reactor (the last treatment unit). There are also several one-tank systems. The most obvious example is a sequential batch reactor The Batch reactor is the generic term for a type of vessel widely used in the process industries. Its name is something of a misnomer since vessels of this type are used for a variety of process operations such as solids dissolution, product mixing, chemical reactions, batch . In a batch system See batch processing. , the reaction environment varies for each stage of the treatment (fill, react, settle, and decant de·cant tr.v. de·cant·ed, de·cant·ing, de·cants 1. To pour off (wine, for example) without disturbing the sediment. 2. To pour (a liquid) from one container into another. ), as described by Bernardes and Klapwijk (1996). Continuous, single-tank systems with varied aeration/mixing patterns can also be designed (Daigger & Littleton, 2000; Littleton, Daigger, Storm, & Cowan, 2003). Even conventional biological wastewater treatment systems may have multiple environmental zones as a result of uneven mixing and aeration, which can result in nitrification and denitrification (Metcalf & Eddy, 2003, p. 623). This inherent capacity may be capitalized upon by a strategic wastewater-loading strategy. For onsite-generated wastewater, the flow is inherently variable. Onsite wastewater is generated in slugs See State and local government series. resulting from specific water usage activities. This circumstance makes controlling the hydraulic loading very simple. The requirements are simply the addition of an equalization In communications, techniques used to reduce distortion and compensate for signal loss (attenuation) over long distances. tank (which can be a septic tank septic tank, underground sedimentation tank in which sewage is retained for a short period while it is decomposed and purified by bacterial action. The organic matter in the sewage settles to the bottom of the tank, a film forms excluding atmospheric oxygen, and ) and a timed dosing system. [FIGURE 1 OMITTED] The research reported here examined the possibility of maximizing nitrogen removal from onsite-generated wastewater by carefully controlling the hydraulic loading (and thus organic and nutrient loading). The existing onsite system selected for the research uses 30 filter socks made from polyester felted material for solid/liquid separation. The socks also allow for the accumulation of a surface biofilm Biofilm An adhesive substance, the glycocalyx, and the bacterial community which it envelops at the interface of a liquid and a surface. When a liquid is in contact with an inert surface, any bacteria within the liquid are attracted to the surface and adhere that may aid in denitrification. Experimental Design Experimental Plan The research was conducted in phases with the goal of maximizing total nitrogen removal. In each phase, a variable or a set of related variables was altered, and the system operated until predictable results were obtained. Experimentation Location The research was conducted at the Western Regional Wastewater Pretreatment pretreatment, n the protocols required before beginning therapy, usually of a diagnostic nature; before treatment. pretreatment estimate, n See predetermination. Facility in Montgomery County Montgomery County may refer to:
System Layout A commercially available onsite wastewater treatment system was used for the research. The unit had a capacity of 500 gal/day and was designed for a single-family residence. Solid/liquid separation was achieved with 30 fabric filter socks. There was a total of 135 f[t.sup.2] of filter surface area. A schematic of the system is given in Figure 1. Influent was fed from a 500-gal/day circular tank that received wastewater from the Montgomery County plant, as previously described. The feed tank filled as needed as needed prn. See prn order. , signaled by a level switch after a drop in volume of approximately 15 percent. A sump pump evacuated e·vac·u·ate v. e·vac·u·at·ed, e·vac·u·at·ing, e·vac·u·ates v.tr. 1. a. To empty or remove the contents of. b. To create a vacuum in. 2. approximately 100 gal from the feed tank every 20 minutes to cause mixing and minimize excessive surface scum build up. The system was dosed in accordance with a set schedule that varied in each research phase, as described in Table 1. The on/off cycle roughly followed the American National Standard/National Sanitation Foundation Method 40 on Residential Wastewater Treatment Systems. This schedule had three loading periods: morning, midday, and evening--6 a.m. to 10 a.m., 11:30 a.m. to 3:30 p.m., and 5 p.m. to 9:30 p.m., respectively. Some minor variations of this schedule did occur between phases. During each of the loading periods, the wastewater was fed for 1 to 6 minutes every 20 minutes. No wastewater entered the system at night (approximately 9:30 p.m. to 6 a.m.). [FIGURE 2 OMITTED] [FIGURE 3 OMITTED] Analysis Grab samples were collected directly in their storage bottles by graduate and undergraduate students. Each data point shown in figures 2 through 8 (to be discussed in the Results Section) represents an independent sampling event. Sulfuric acid sulfuric acid, chemical compound, H2SO4, colorless, odorless, extremely corrosive, oily liquid. It is sometimes called oil of vitriol. Concentrated Sulfuric Acid was added beforehand to preserve the samples to be analyzed for nitrogen. All samples were transported to the laboratory in a cooler. BO[D.sub.5] and TSS analyses were conducted within four hours of collection. The other samples were stored in a refrigerator. Influent samples were obtained from the feed tank's recirculation Noun 1. recirculation - circulation again circulation - the spread or transmission of something (as news or money) to a wider group or area line (used to keep the tank mixed, as previously described). Effluent samples were collected from the effluent line, which was continuously free flowing. The analytical methods are referenced in Table 2. Hach Company methods and a micro-processor-controlled spectrophotometer spectrophotometer, instrument for measuring and comparing the intensities of common spectral lines in the spectra of two different sources of light. See photometry; spectroscope; spectrum. were used for the nitrogen analyses and are believed to be adequate for research of this type, although they are not approved by U.S. EPA. Dissolved oxygen and temperature were not measured because of the difficulty of routinely and safely accessing the aeration portion of the treatment system. Oxygen deficiencies were not expected, however, for the onsite wastewater treatment system used in this research. The wastewater temperature was expected to stay fairly consistent since the source was a publicly owned Publicly owned can refer to:
sewage system, sewage works facility, installation - a building or place that provides a particular service or is used for a particular industry; "the , and the onsite unit was in the screening room located at the same depth as the plant influent sewer. To assess analytical quality, the authors analyzed over 30 percent random duplicates. When a high-percentage recovery resulted, corrective action A corrective action is a change implemented to address a weakness identified in a management system. Normally corrective actions are instigated in response to a customer complaint, abnormal levels if internal nonconformity, nonconformities identified during an internal audit or was taken, and samples in the suspect batch were rerun re·run n. The act or an instance of rebroadcasting a recorded movie or a recorded television performance. tr.v. re·ran , re·run, re·run·ning, re·runs To present a rerun of. if possible; the data were discarded if the samples could not be rerun. Table 2 contains the percent relative range and other related data for each parameter. Periodic blanks, standards, or both were also assessed for TSS, ammonia, nitrate, pH, and alkalinity al·ka·lin·i·ty n. The alkali concentration or alkaline quality of a substance that contains alkali. alkalinity 1. the quality of being alkaline. 2. . Results indicated that there were no quality problems (data not shown). Results and Discussions Throughout the research period, the onsite wastewater treatment unit demonstrated consistent and predictable operation with few upsets. The filter socks did not clog and were replaced only once between phases 3 and 4 as part of routine maintenance. Figures 2 and 3 show the levels of BO[D.sub.5] and TSS, respectively, for each phase, as described in Table 1. Figures 4, 5, and 6 show the nitrogen series results (TKN, ammonia, and nitrate, respectively). Total nitrogen was calculated by addition of TKN (which includes ammonia) and nitrate, and the result is shown in Figure 7. Nitrite nitrite Any salt or ester of nitrous acid (HNO2). The salts are inorganic compounds with ionic bonds, containing the nitrite ion (NO2−) and any cation. was not measured because it was assumed to be too low to influence the total nitrogen values. In Figure 7, "potential" total nitrogen represents the amount that would be in the effluent if no nitrogen removal occurred. Table 3 summarizes all of these data. [FIGURE 4 OMITTED] As is evident in Figure 2 and Table 3, the effluent BO[D.sub.5] was consistently low regardless of the research phase (hydraulic loading and instantaneous flow). The highest value during the entire research project was 15 mg/L; however, most values were substantially lower. Similarly, the effluent TSS (Figure 3 and Table 3) concentrations were consistently low, with the exception of a few spikes that could not be traced to specific causes. [FIGURE 5 OMITTED] After the system had been operating for approximately 1 month; the effluent TKN (Figure 4 and Table 3) was consistently below 10 mg/L of nitrogen (10 mg/L-N), regardless of the varied operating conditions. Similarly, ammonia effluent levels (Figure 5 and Table 3) were, with some exceptions during phases 3 and 4, below 5 mg/L-N. The effluent nitrate (Figure 6) tended to be slightly lower in the latter two phases. The level of total nitrogen in the effluent was lower, and more consistent removal of total nitrogen occurred (Figure 7), in the latter phases, when the instantaneous flow rate was substantially reduced. The daily average flow appeared not to be as important as the instantaneous loadings in reducing the total nitrogen level. Nitrogen can be removed from wastewater by the following mechanisms: * ammonia stripping; * removal of solids containing nitrogen in the effluent TSS, wasted sludge, or both; or * microbiological transformation of TKN and ammonia to nitrate followed by biodegradation Biodegradation The destruction of organic compounds by microorganisms. Microorganisms, particularly bacteria, are responsible for the decomposition of both natural and synthetic organic compounds in nature. of nitrate to nitrogen as a result of denitrification. Ammonia stripping was not likely because at a close to neutral pH and without an engineered stripping unit, ammonia is largely in the ion form, which is not volatile (Corbitt, 1989; Metcalf & Eddy, 2003, p. 1179). The only solids that were routinely released from the system were effluent TSS. As shown in Figure 3 and Table 3, these values were consistently very low. These results indicate that substantial microbiological denitrification occurred. Another indicator of microbiological nitrification and denitrification is changes in alkalinity and pH between the influent and effluent. Alkalinity levels are reduced during nitrification, and while they increase by about half the amount lost during denitrification, the end result is a net decrease in alkalinity (Metcalf & Eddy, 2003, p. 620). Nitrification results in a decrease in pH, and denitrification results in a substantial increase in pH (Metcalf & Eddy, 2003, p. 622). As shown in Figure 8 and Table 3, the pH of the influent wastewater was lower in the last two phases of the research. As real wastewater was being used, this result can only be attributed to a change in user discharge characteristics. At a pH below 6.8, the rate of nitrification substantially decreases (Metcalf & Eddy, 2003, p. 615). There was also a corresponding decrease in ammonia removal, as shown in Figure 5 and Table 3. Figure 9 and Table 3 show an increase in alkalinity in phases 3 and 4. This result indicates a disproportionate amount of denitrification (compared with nitrification), which is not as sensitive to low pH values as nitrification. This trend is seen in Figure 8 and Table 3, which show substantial increases in pH in phases 3 and 4. Although the changing influent wastewater conditions prevent precise modeling, the above analysis provides strong evidence that biological nutrient removal occurred. [FIGURE 6 OMITTED] [FIGURE 7 OMITTED] Conclusions Enhancement of total nitrogen removal may be possible in any aerobic system through control of hydraulic loadings, the dissolved oxygen level, and mixing patterns Mixing patterns refer to systematic tendencies of one type of nodes in a network to connect to another type. For instance, nodes might tend to link to others that are very similar or very different. (Metcalf & Eddy, 2003, p. 623). This research demonstrated that reducing the instantaneous influent flow by spreading it into periods of no flow allowed the loading of nitrogen to more closely balance the inherent nitrogen removal capacity of the specific unit tested. The intermittent nature of onsite wastewater generation conveniently allows for this hydraulic-loading strategy. The only requirements are a storage tank for equalization, a dosing pump, a controller, and a passive bypass in case pump failure occurs. It is not uncommon to find large septic tanks that can provide the basin for equalization positioned before onsite wastewater treatment systems, which further simplifies the requirements for existing units. Each onsite wastewater treatment unit has a unique denitrification capacity that can only be determined experimentally. The onsite wastewater treatment unit used in the research reported here is believed to be particularly suited for high nitrogen removal because of the possibility of denitrifying bacteria denitrifying bacteria: see nitrogen cycle. denitrifying bacteria Soil microorganisms whose action results in the conversion of nitrates in soil to free atmospheric nitrogen, thus exhausting soil fertility and reducing agricultural productivity. attachment to the solid/liquid sock separators. Acknowledgements: This research was funded by Consolidated Treatment Systems, Inc., of Franklin, Ohio Franklin is a city in Warren County, Ohio, United States. The population was 11,396 at the 2000 census. History Franklin was founded by General William C. Schenck, in 1796. The settlement was named for Benjamin Franklin. , and its Multi-Flo[TM] Model FTB-0.5 was used as the onsite wastewater treatment unit. Some funding for graduate students was provided by the Dayton Area Graduate Studies Institute. The authors thank Jessica L. Jacobs, Ella Mashingaidze, and Jean-Fernand Krou for assisting in the collection and analysis of samples. The authors also thank the Montgomery County, Ohio, Sanitary Engineering
Authors' Note: This manuscript is dedicated to the memory of Robert Parker Robert Parker may refer to:
Corresponding Author: Steven I. Safferman, Associate Professor, Department of Biosystems and Agricultural Engineering Agricultural engineers develop engineering science and technology in the context of agricultural production and processing and for the management of natural resources. The first curriculum in Agricultural Engineering was established at Iowa State University by J. B. , Michigan State University Michigan State University, at East Lansing; land-grant and state supported; coeducational; chartered 1855. It opened in 1857 as Michigan Agricultural College, the first state agricultural college. , 202 Farrall Hall, East Lansing East Lansing, city (1990 pop. 50,677), Ingham co., S central Mich., a suburb of Lansing, on the Red Cedar River; inc. 1907. The city was first known as College Park, but was renamed when it was incorporated. , MI 48824. E-mail: Safferma@msu.edu. [FIGURE 8 OMITTED] [FIGURE 9 OMITTED] REFERENCES Bernardes, R.S., & Klapwijk, A. (1996). Biological nutrient removal in a sequencing batch reactor Sequencing batch reactors (SBR) or sequential batch reactors are industrial processing tanks for the treatment of wastewater. SBR reactors treat waste water such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. treating domestic wastewater. Water Science and Technology, 33(3), 29-38. Corbitt, R.A. (1989). Standard handbook of environmental engineering. New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of : McGraw-Hill. Daigger, G.T., & Littleton, H.X. (2000). Characterization of simultaneous nutrient removal in staged, closed-loop bioreactors. Water Environment Research, 72(3), 330-339. Eaton, A.D., Clesceri, L.S., Greenberg, A.E., Franson, M.A.H., American Public Health Association The American Public Health Association (APHA) is Washington, D.C.-based professional organization for public health professionals in the United States. Founded in 1872 by Dr. Stephen Smith, APHA has more than 30,000 members worldwide. , American Water Works Association American Water Works Association (AWWA) is an international nonprofit professional organization dedicated to the improvement of drinking water quality and supply. It was founded in 1881 and, as of 2007, there are approximately 60,000 AWWA members world-wide. , & Water Environment Federation (1998). Standard methods for the examination of water and wastewater (20th ed). Washington, DC: American Public Health Association. Hach Company. (1997). Water analysis handbook (3rd ed). Loveland, CO: Author. Littleton, H.X., Daigger, G.T. Storm, P.F., & Cowan, R.A. (2003). Simultaneous biological nutrient removal: Evaluation of autotrophic denitrification, heterotrophic nitrification, and biological phosphorus phosphorus (fŏs`fərəs) [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1°C;; b.p. about 280°C;; sp. gr. 1.82 at 20°C;; valence −3, +3, or +5. removal in full-scale systems. Water Environment Research, 75(2), 138-150. Metcalf & Eddy. (2003). Wastewater engineering (4th ed.). Boston: McGraw Hill. Multi-Flo Waste Treatment Systems, Inc. (1993). Owner's manual: On-site waste treatment system, Multi-Flo (Document 010-0593). Franklin, OH: Consolidated Treatment Systems, Inc. U.S. Environmental Protection Agency. (2000). Onsite wastewater treatment systems manual (EPA 625/R-00/008). Retrieved September 15, 2005, from http://www.epa.gov/ordntrnt/ORD/NRMRL/pubs/625r00008/html/html/625R00008.htm#Notice. Steven I. Safferman, Ph.D., P.E. Marianna I. Novellino Bennette D. Burks, P.E. Robert A. Parker
TABLE 1 Research Phases
Hydraulic Dose
Volume/Dose Instantaneous
Phase Start/End Days (gal) On (min) Off (min) Flow (gal/min)
1 0/181 12.7 0.75 20 16.9
2 182/258 6.1 0.75 20 8.1
3 259/353 7.4 6 2 1.2
4 354/380 7.4 6 2 1.2
Hydraulic Dose
Total Flow
Phase Start/End Days (gal/day) Modifications
1 0/181 500
2 182/258 250 The daily hydraulic loading was
reduced by half by a reduction in
the instantaneous flow.
3 259/353 500 The hydraulic load was increased.
The instantaneous flow rate was
reduced.
4 353/380 500 The system was cleaned and solids
removed as part of routine
maintenance.
TABLE 2 Analytical Methods (a)
Quality Assurance/
Parameter Unit Duplications
5-day carbonaceous biochemical mg/L [O.sub.2] % relative range
oxygen demand (BO[D.sub.5]) Standard deviation
Number of values
Total Kjeldahl nitrogen (c) (TKN) mg/L-N % relative range
Standard deviation
Number of values
Ammonia (N[H.sub.4]) mg/L-N % relative range
Standard deviation
Number of values
Nitrate (N[O.sub.3]) mg/L-N % relative range
Standard deviation
Number of values
Total suspended solids (TSS) mg/L % relative range
Standard deviation
Number of values
pH No duplications
Alkalinity mg/L % relative range
Ca[CO.sub.3] Standard deviation
Number of values
Quality Assurance/
Parameter Duplications Method
5-day carbonaceous biochemical 14 Standard
oxygen demand (BO[D.sub.5]) 9 methods, (b)
29 Method 5210 B
Total Kjeldahl nitrogen (c) (TKN) 10.6 Hach (d) 8075
9.1
21
Ammonia (N[H.sub.4]) 16.4 Hach (d) 10023
26.8
29
Nitrate (N[O.sub.3]) 7.6 Standard
19.8 Methods, (b)
30 4110 C (e)
Total suspended solids (TSS) 33 Standard
49 methods, (b)
77 Method 2540 D
pH No duplications Standard
methods (b)
Alkalinity 2.9 Hach (d) 8203
2.9
24
(a) Procedures were from Hach's Water Analysis Handbook (1997).
(b) Standard methods: Standard Methods for the Examination of Water and
Wastewater (Eaton et al., 1998).
(c) Measured ammonia and organically bound nitrogen in the trinegative
state after digestion with the Hach Co. Digesdahl digesting procedure.
(d) Hach: Standard test methods and kits provided by Hach, Inc.
(Loveland, Colorado).
(e) Shimadzu HPLC with a conductivity detector and a Hamilton PRPX100
Anion Column.
TABLE 3 Analytical Parameters
Phase
1 2
Parameter Influent Effluent Influent Effluent
BO[D.sub.5] (mg/L)
Average 204 5 591 3
Standard deviation 75 4 331 1
Number values 20 15 5 3
TSS (mg/L)
Average 215 10 356 11
Standard deviation 122 13 272 19
Number values 13 15 4 4
Ammonia (mg/L-N)
Average 19 2 23 1
Standard deviation 4 0.7 8 1
Number values 19 15 5 5
Nitrate (mg/L-N)
Average 0.2 7 BDL 14
Standard deviation 0.2 4 -- 6
Number values 19 19 5 5
TKN (mg/L-N)
Average 32 7 46 3
Standard deviation 9 6 15 1
Number values 18 18 6 4
Total N (mg/L-N)
Average 32 13 43 10
Standard deviation 9 5 18 16
Number values 16 17 4 4
pH
Average 6.9 7.2 6.3 7.1
Standard deviation 0.3 0.2 0.4 0.4
Number values 21 21 6 6
Alkalinity (mg/L
CaC[O.sub.3])
Average 237 184 277 198
Standard deviation 24 28 31 53
Number values 20 20 6 6
Phase
3 4
Parameter Influent Effluent Influent Effluent
BO[D.sub.5] (mg/L)
Average 323 1 724 7
Standard deviation 77 2 39 3
Number values 5 6 4 4
TSS (mg/L)
Average 140 2 171 4
Standard deviation 46 3 43 7
Number values 11 11 5 5
Ammonia (mg/L-N)
Average 18 3 23 4
Standard deviation 5 3 4 2
Number values 11 11 5 5
Nitrate (mg/L-N)
Average BDL 3 BDL 1
Standard deviation -- 2 11 1
Number values 11 11 5 5
TKN (mg/L-N)
Average 53 5 48 8
Standard deviation 16 2 13 2
Number values 8 8 5 5
Total N (mg/L-N)
Average 53 9 48 9
Standard deviation 16 4 13 2
Number values 8 8 5 5
pH
Average 6.0 6.9 5.6 6.9
Standard deviation 0.1 0.1 0.1 0.1
Number values 11 11 5 5
Alkalinity (mg/L
Ca[CO.sub.3])
Average 250 270 246 358
Standard deviation 31 57 37 12
Number values 9 9 5 5
BDL = below detection limit.
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