Parameter Descriptions

Total suspended solids testing is a mainstay of most water discharge permits. Design engineers can use a clarifier or a sand filter to remove TSS. Most wastewater plants now have limits of 15 mg/l TSS. Because the TSS can be calculated as a load that must be removed to meet a discharge limit, it is more useful for the plant. There are no water quality standards for TSS other than general statements. “Receiving waters shall have no distinctly visible solids, scum or foam of a persistent nature, nor shall there be any formation of slime, bottom deposits or sludge banks.”

The TSS method is straight forward. A weighed glass fiber filter is used to filter 200 ml of sample, the filter is then dried and reweighed and the difference of weights, corrected to a liter, is the TSS. QA is through testing of duplicate samples, a lab control standard, and calibration of the analytical balance.

Turbidity is a measure of the clarity of a stream, which depends on the amount of TSS present. It is expressed as nephelometric turbidity units. The NTU is a measure of 90 degree angle light scattering, which can have a relationship with TSS for a specific water body, but not a factor generally applicable to multiple streams or lakes. Turbidity has standards listed in Regulation 2, Water Quality Standards, and the numbers vary depending on the ecoregion and type of water body. Limits are lower in the Ozarks and Ouachitas, since streams and lakes are naturally much clearer. The Delta turbidity limits are much higher due to the soil substrate of the streams and stream banks. The other ecoregions are somewhere in between. The south part of the Arkansas River Valley is fairly turbid in streams like the Petit Jean River. Lakes Bull Shoals, Greers Ferry, and Ouachita have the lowest turbidities in the state as a rule.

Turbidity is analyzed by a turbidimeter that is calibrated to directly report in NTU. Formazin standards are used for calibration and duplicates are checked for QA reporting.

TSS/turbidity problems happen with stormwater at construction sites, on-stream gravel and sand mining, filter backwash at water treatment plants, non-point runoff from agricultural activities, etc. Unstable stream banks contribute large amounts of solids and turbidity during high flow events.

To get an idea of turbidity amounts, a turbidity of less than 1 might let you see the bottom of a lake that is 10+ feet deep. A 10 turbidity would let you see your feet in 3-4 feet of water. A turbidity of 100 would allow visibility of a couple of inches. Sight feeding fish would be at a disadvantage at higher (50+) turbidities.

The anions testing includes chlorides, bromides, fluorides, sulfates, and, if calibrated for them, nitrates and phosphates. However, the nitrates and phosphates are done by other methods in the ADEQ lab. Chlorides and sulfates are limited by Regulation 2 in all waterways. The standards vary from ecoregion to ecoregion and often waterway to waterway. The secondary drinking water standard is 250 mg/l for both parameters, and the majority of the Reg. 2 standards are well below 250. The drinking water standards are set at 250 for chloride due to salty taste at 500 and the 250 for sulfates is due to GI distress at 500 and above.

Anions are analyzed by an ion chomatograph. The IC uses a column to separate the anions, then a conductivity detector to measure the amounts. Of course, like most of the ADEQ instruments, the IC has an autosampler for injecting samples, a data system for methods and data calculation, and a connection to the laboratory information management system. The test results are stored in the LIMS with the other test results for each sample. QA is through initial calibration, continuing calibration standards, duplicates, and spikes.

Natural levels of chlorides range from zero to about 300 mg/l. the low numbers are in the Ouachita ecoregion and Ozarks and the high end is in the Arkansas River and Red River. The most common type of chloride contamination is from oil and gas operations. There are salt flats in southern AR, caused by oil production many years ago, that do not grow vegetation. More recent problems have been attached to the Fayetteville shale gas production. The oil production brines in the south routinely run about 50,000 mg/l. Although the gas wells generate wastes that are around 1,000 to 10,000 mg/l, the amount of wastewater for each well is far greater, causing disposal problems.

Bromides and fluorides are not significant in the natural waters of the state. Ambient monitoring samples rarely exceed 1 mg/l for either test. Problems have happened near the bromine plants for bromides and at the potliner incinerator for fluorides.

Oxygen levels are specified in water quality standards. Most warm water has a 5 mg/l standard with as low as a 2 mg/l critical value. In the 2-5 range, most fish and aquatic life will survive, but won’t thrive. At less than 2 mg/l mortality begins. Trout waters require higher minimum O2 levels, so standards are 6 with a 6 critical.

Oxygen problems occur when biodegradable organics use up existing oxygen in a waterway. Wastewater treatment plants control the amount of organics so that the receiving stream maintains an oxygen level that sustains aquatic life. However, if non-point sources like animal waste or septic tanks are present, oxygen levels could be compromised by those loads and others. The speed of recovery to normal levels is determined by aeration by wind action, turbulence, and photosynthesis. Waters of the delta area of eastern Arkansas and the gulf coastal plain of south Arkansas are often lower in oxygen than the waters of the mountainous areas of the west and north due to low aeration. The west and north will often have O2 at near saturation (~7-13 mg/l based on temperature) while other areas will normally be less saturated. An observed value that is higher than saturation usually denotes a lot of vegetation or algae present. The levels may be 200% saturation in the daylight, but may be 0 at dawn due to photosynthesis then respiration.

Oxygen problems in Arkansas are most notable at the discharges of the deep Corps of Engineers lakes. Because the cold, stratified water at the bottom of the lakes is low in oxygen, the water remains low when released through the turbines. Other problems are noted periodically in the summer in both slow streams and farm ponds, and usually cause fish mortality.

Dissolved oxygen is analyzed by an oxygen meter, and is used in the field for measurements. There is no holding time for samples, and the act of collecting a sample may change the oxygen level, so a direct probe reading is the appropriate method. The meter is air calibrated with moist air in an enclosed container. Quality assurance is through recording the calibration for accuracy and doing a field duplicate for precision.

Metals testing at ADEQ includes toxic metals like cadmium, barium, copper, lead, nickel, chromium, arsenic, silver, and selenium; hardness causing metals like calcium, magnesium, iron and manganese; water use metals like sodium and potassium; other metals like aluminum, antimony, cobalt, thallium, vanadium, zinc; and boron. Mercury is also analyzed, but mostly on fish samples by a method specific for mercury. All the metals except mercury are analyzed by an inductively coupled plasma/mass spectrometer. The ICP/MS performs the testing in about 3 minutes for the list above. On water samples, the detection limits are near or below a ppb for the metals of concern in water quality standards, since the standards are set in the low ppb levels. The standards are hardness based, since metals are more toxic at lower hardness concentrations.

ICP/MS testing requires multiple types of quality control. First, the instrument has to be calibrated against reference standards over the normal measuring range. Second, the instrument has to be checked with an interference standard to assure that none of the amounts are affected by positive or negative interferences. Third, blanks must be analyzed—method, reagent, DI water, field, etc. Fourth, continuing calibration standards have to be analyzed throughout the testing. Beyond this, the typical QA must be done—duplicates, spikes, spike duplicates, etc.

ADEQ uses both total metals and dissolved metals for assessment. Dissolved metals are immediately filtered in the field through 0.45 micron filters. Totals are whole water samples that are acid digested in the lab to prepare for testing. Because of the digestion, the more turbidity in a sample, the more metals are found. Natural soils contain enough metals to cause elevated totals. Dissolved metals reflect only the metals in solution. For this reason, totals in south and east AR are higher than the less turbid ecoregions. The dissolved metals are generally low throughout the state, barring a direct source.

Mercury is analyzed by a mercury analyzer. It produces a mercury vapor from a sample, and then measures the vapor to relate back to the sample concentration. Mercury is not routinely tested in water, since it has only rarely been positive. Fish samples are tested totaling about 50 samples per year. Mercury is present in most fish samples, and often over the FDA limit of 1 ppm. The results are sent to the Health Dept. for evaluation for fish consumption advisories.

Mercury in fish is present as methyl mercury for the most part. Methyl mercury is produced by sulfur reducing bacteria if there is sufficient sulfates and TOC, low pH and alkalinity, and an anoxic zone present. The bacteria use sulfates to make H2S in the anoxic zone and, at the same time, make inorganic mercury into methyl mercury. There is sufficient inorganic mercury in the soils of AR to produce methyl mercury, but the other conditions are often not met, therefore keeping most fish safe to eat.

Organic chemicals take several forms in testing. We test for volatile organics, semivolatile organics, and pesticides. In the ADEQ lab pesticides are a special type of semivolatile testing. Volatiles and semivolatiles are analyzed by a gas chromatograph/mass spectrometer, but the preparation of the samples and the introduction into the GC/MS are different.

Volatile samples are collected in a vial with no air bubbles. The samples are then placed into an autosampler that pumps the sample into a “purge and trap” unit, then the purge and trap bubbles helium gas through the sample to carry the volatile components to an absorbent trap. When the process is completed, the trap is heated to sweep the volatiles into the GC/MS for analysis. QA for this analysis includes verification of a tuning compound, calibration with each analyte, internal standards, surrogate chemicals introduced into the samples, field duplicates, spikes, etc.

The volatile chemicals covered in this test include components of gasoline, dry cleaning fluid, paint strippers, degreasing solvents, and other solvents. The method has detection limits in fractions of ppb’s. Concern levels are in the low ppb level, since many of drinking water standards are in that range. Problems in AR include gasoline leaks and spills, industrial waste solvents leaks and spills, landfill leachate, etc.

Semivolatiles are collected in precleaned 1-liter glass bottles. Testing requires an extraction of the water sample by methylene chloride, then the solvent is concentrated to 1 ml. During the prep an internal standard and surrogate standards are added to the sample. The extract is then placed in a vial and the vial placed into the autosampler for the GC/MS. The sample is then injected into the instrument for analysis. QA is essentially the same for semi’s as volatiles, however the compounds are not the same.

Semivolatiles include phenols, creosote components, phthalates (plastisizers), pesticides, and others. Many of the semivolatiles are solids at normal temperatures, but some are liquids. Problems in AR include pentachlorophenol and creosote components at wood treating sites, and their cleanup. Pesticides cause fish kills and non-target plant kills, but ambient samples rarely contain pesticides, since most are quickly degraded in the environment. Atrazine used on corn is the most common pesticide found. In the past, pesticides like DDT, toxaphene, chlordane, and other chlorinated hydrocarbon insecticides and PCB’s were often found, but they have been banned for several decades. The only recent positive was at a house where bags of DDT and other insecticides were stored in the crawl space. PCB’s are still found at Lake Saracen from a spill that happened over 30 years ago. Phthalates are plastisizers that make plastics flexible. They are found in most samples analyzed, but at low levels.

ADEQ tests for both Fecal Coliform and Escherichia coli bacteria. Most of the testing is to verify compliance with permits, but some ambient monitoring is done to assess waters for the 305b status and 303d impaired waters reports. Reg. 2 standards are 200 colonies/100 ml average and 400 maximum for fecal coliform during body contact months and 1000/2000 during colder months. E. coli limits are 126 colonies/100 ml average and 298 max or 410 max depending on the designation of the water body. The cold month numbers are 630/1490 or 2050. The averages are geometric means. The higher numbers for the cold months allow wastewater plants to shut off their disinfection system to cut costs. The two tests are used to show that the waterway has been exposed to animal waste within a few days of the test. Neither parameter can exist in the environment for longer than the few days. The bacteria prefer the warm-blooded animal GI system and anaerobic conditions to grow.

The method for both tests is the same. A water sample is filtered through a filter that has pores small enough to catch bacteria. The filter is then transferred to a petri dish with media that grows the bacteria. Fecal coliform and E. coli are differentiated by the media used in the test. The fecal coliform media grows colonies of bacteria that turn blue. The colonies each represent a single bacterium present on the filter before incubation. The E. coli media grows colonies of E. coli that have a blue color after incubation. Quality Assurance is through field duplicates, method blanks, etc.

Bacteria problems in AR are usually related to animal waste issues, whether it’s from an overflowing waste pond or improper disposal of chicken litter or stormwater runoff from a feedlot or pasture. In many of these situations the bacterial count may be 100,000 or more per 100 ml in the affected stream or impoundment. Another source is sanitary sewer overflows at manholes and leaks from faulty sewer pipe. Of course, the common site in rural AR is the cattle in the farm pond.