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Home My WebLink About1983-10-03 Henn Co Lake Water AnalysisCOMMUNITY HEALTH DEPARTMENT ENVIRONMENTAL HEALTH MANAGEMENT GROUP Suites 202-206 HENNEPIN 32 Tenth Avenue South LFUHopkins, Minnesota 55343 October 3, 1983 Ms: Penny Grabek 960 re f Arms Lane Mound N 55364 War Ms-Grabek: L L L f • is The results of the water samples taken from Forest Bay of Lake Minnetonka on September 21, 1983 at 9:30 am are as follows: Location of Sample Fecal Coliform Fecal Streptococcus Shore 30/100 ml 40/100 ml Boat channel 980/100 ml (*} 560/100 ml (*) Plates were too overgrown with bacteria to court coliform. Counts were estimated. The Recommended Standards for Bathing Beaches of the Great Lakes -upper Mississippi River Board of Sanitary Engineers, 1975 Edition, which is used as a guide by the Minnesota Department of Health states that for bacteriological quality "The fecal coliform density from the last five successive sets of samples collected on five different days shall not exceed a geometric mean of 200 per 100 mt,'� When the fecal coliform density of any sample collected exceeds 1,000 per 100 ml consideration should be given to closing the bathing beach, and daily sample shall immediately be collected and analyzed for fecal coliform for at least two consecutive days." The coliform count was not found to be so high in the samples collected to recommend that the lake not be used for swimming. There are no recommended maximum levels for fecal streptococcus the presence of which is used as a indicator of animal fecal material. We have no guidelines for interpreting the number of fecal streptococcus found in the samples that were taken at Forest Bay of Lake Minnetonka. HENNEPIN COUNTY an equal opportunity employer I would caution you against making conclusions of pollution by human or animal waste based on these sample. Much more should be known about the levels of bacteria in the lake during other times of the year, the quality of residential septic systems on the land adjacent to the lake, and the amount of animal waste that enters the lake from all domestic and wild animals. I hope that we have provided you with some help. Sincerely, Roge Carlson Senior nvironmentalist RHC/vp P-2 only 0.1% pollutants which need to be removed. Wastewater treatment is difficult because it is necessary to maintain a very high removal efficiency while dealing with large volumes of water. The 0.1% in wastewater that must be removed or modified consists mostly of organic material, bacteria, and nutrients. The organic material, which is sometimes called the "biochemical oxygen demand" (BOD), comes from a variety of. sources in a domestic wastewater system. Food preparation, dish and clothes washing, and wastes from the relatively inefficient human .digestive system all discharge into the domestic sewage system. Table B.1. shows the concentration of BOD, suspended solids, and other materials in raw sewage and in septic tank effluent. BOD and suspended solids are measures of the percentage of organic material found in wastewater. Pathogens are microorganisms which cause disease and are usually present in domestic sewage. Fecal coliforms are indicators of the presence of pathogens and Table B.1. shows that in 100 ml (about 112 cup) of septic tank effluent, there are between 1,000 and 1 million. There are about the same number of viruses in this quantity of effluent. Nutrients are part of the materials in septic tank effluent and are of concern because of possible eutrophication of ground or surface waters and possible contamination of water supply wells. Nitrogen and phosphorus are the nutrients of major concern in sewage tank effluent. Quantities of these nutrients are listed at various locations in the soil treatment system in Table B.1. Table B.1. Treatment Efficiencies of Soils One Foot Three Feet Raw Septic Tank Below Trench Below Trench Parameter Waste Effluent_ Bottom Bottom BOD5 (mg/1) 270 - 400 140 - 175 0 0 TSS (mg/1) 300 - 400 45 - 65 -_ 0 0 Fecal Coliform �1 1 million to thousand to 0 - 100 0 (MPN/100 ml) 100 million million Viruses (Unknown) 11 100 thousand to 0 - 1000 0 (PFU/ml) 10 million Nitrogen Total (mg/1) 100 - 150 50 - 60 - _ NH4 (mg/1) 50 - 120 30 - 60 *B - 60 B NO3 (mg/1) < 1 t B - 40 B - 40 Total Phos- phorus (mg/1) 10 - 40 10 - 30 B - 10 B - 1 * B = c3ackground ')h SE'PlAC LANK SYSII^I I'.FI•F.C•IS ON ( ROUND WAILK Q('AI.I Il GROUNI) Tablc 23 summarizes the bacteriological character of household septic Soil Absorption System 1 tank effluent (Siegrist, 1977; and University of Wisconsin, 1978). The quantities of indicator bacteria such as fecal coliform are high, and Viraraghavan and 1 pathogenic bacteria such as Pseudomonas aeruginosa, have commonly been the primary objective ( isolated. In addition, results of analyses for Staphylococcus aureus and (drainfield tile) systern salmonellae have indicated their presence in septic tank effluents, FuTonly concentration of various infrequently and in rT lower concentrations (10 homes, 6 of 63 samples the septic tank effluent positive at 10-1000/1(,� ml and 11 homes, 2 of 55 samples positive at 3.4- the soil at which soi. v 2201100 ml, respectively) (Siegrist, i977). Viruses in septic tank effluents effects of air and soil t are high only if infections have occurred. Salmonellae have been detected efficiency of the septic 1 in 59 percent of 17 different septic tank pumpout sludges, which shows site of the study was ne clearly that septic effluents need to be purified before release to eithor conditions in this reg ground water or surface water (Bouma, 1979). temperatures, usually wi Table 23: Summary of Bacteriological Character of Household Septic spring when ground watt the �jil ampies taken fr( Tank Effluents was sandy clay for the i less sand at depths of 2 1 septic tank effluent app Number 95. Confidence results of the field stud' of Mean Interval indicated the followinf, fr Reference Organism Samples (NO./100 ml) (No./100 ml) -------_--___-- _—_-- 1. The soil t-ad percent) Ui 1 1 Total present in the bacteria 88 3.4xlUb 2.5 to 4.8x1U8 2. Reductions o• l Total range, much coliform 91 3.4x1O6 2.6 to 4..'4x1U6 has special si substantial an t Fecal be added to la coliform 94 /" 4.2x1O5 2.9 to 6.Tx1U5 (\ L 2t' C � t7 3. High ammonia Fecal coliform 151-S:(nt106 �.5x106 to 1.Ox107 an increase i nitrification oc-C),cre'D nitrate build - 1 Fecal possible hea1C streptococci 97 3.k:_ 2.0 to 7.2x103 4. Efficiency wi 2 Fecal greater effit streptococci 155 4.Ox1O4 8.Ox1U3 to 2.Ox105 parameters d fromSeptemt 1 Pseueomonas was greater. ' Aeruginosa 33 8.6x103 3.8 to 19.0x103 to 75 percen; _ percent for ar water levels e Reference 1 Siegrist (1977), data from 5 tanks. a declining to Reference 2 University of Wisconsin (1978), data from 7 tanks. Soil Absorption System E, Based on the ab reductions relative to t