| Federal Guidelines for effluent discharge covering "toxic pollutants" require BAT (Best Available Technology Economically Achievable) and guidelines for "non-conventional pollutants" require BPT (Best Practicable Control Technology Currently Available). These guidelines are technically bases, ie. on the potential of various treatment processes, and are presented in terms of allowed pollutant quantities per unit of production. The Federal discharge permit is usually issued based on the following tests: |
| A) Conventional pollutants - BOD5 - Five-day biochemical oxygen demand SS - suspended solids pH |
| B) Non-Conventional pollutants
- COD - chemical oxygen demand Sulfides Phenols Total Chromium |
| In some states, the stream/river discharge standards are even more stringent than the Federal effluent standard and can set discharge limits for dissolved oxygen, temperature, oil and grease, and specific chemical concentrations, measured in ppm or mg/l, of such pollutants as ammonia, acrylonitrite, cyanide, etc. The coloring in the dyes is generally not subject to regulation since dyes are resistant to degradation and the quantities discharged are usually low. |
| The size of an aerated lagoon is usually calculated to allow for a hydraulic retention time of from 5 to 100 days, or more. Aeration devices supply both oxygen and mixing. The waste stream from an aerated lagoon is normally sent to a clarifier, to allow the biomass to settle out before the clear supernatant is discharged over a weir and the settled sludge (biomass) is recycled to the aeration basin. Excess sludge is sometimes removed for land application, or is sold as "Miloginite". |
| An activated sludge system is selected when a biomass two to twenty times that of an aerated lagoon is required. Bacteria can grow to this concentration because they are kept in the system independently of hydraulic retention times. |
| While the textile industry uses a number of compounds found in the EPA's list of Priority pollutants, the discharge levels of only phenol and COD are specifically cited by Federal Regulation and are closely monitored. The term phenol is interpreted to define phenolic compounds, many of which are more detrimental than pure phenol. They are susceptible to biodegradation, especially when the selected bacterial cultures in Alken Clear-Flo® 7002 are used. |
| Since the textile industry is extremely market-driven, responding to customer demand to produce specific colors and fabrics, the quantity and content of the waste varies widely from day to day. The two most common treatment designs employed by the textile industry are aerated lagoons and activated sludge. |
| Dyes are selected for their resistance to oxidation and are therefore very difficult to degrade. In an activated sludge system, dyes are generally removed physically by being adsorbed on floc. While this solution is effective for basic dyes and direct dyes, acid dyes and reactive dyes are poorly adsorbed. Azo and triphenyl-methane dyes can be slowly biodegraded under aerobic and aerophyllic conditions. Azo dyes can be decolored under anoxic or anaerobic conditions. Dyes also contain carriers which can usually be classified as chlorinated aromatics, aromatics (such as ortho-dichlorobenzene, trichlorobenzene, and ortho-chlorotoluene), alkylated aromatics, and pthalate esters. Under certain circumstances, biphenyl is added to the formulations to extend the yield of the dyestuff. |
| When employing chelating agents, such as EDTA, to sequester metallic ions (chiefly Ca, Mg, Fe, Cu), great care should be taken to maintain the ratio of Fe to stabilized BOD of 0.5 lbs. Fe per 100 lbs. BOD stabilized. If toxicity to fish is a concern, one must be aware that reduced surface tension, caused by the presence of surfactants in a quantity exceeding 45 dynes/cm. in the waste stream, will inhibit the breathing ability of fish. |
| Foam is another frequently encountered treatment problem. A sudden influx of surfactant from an aeration basin can cause a stiff, stable foam to cover the entire treatment basin to a depth of three feet. If wind catches this foam, large pieces can be blown onto the surrounding property. This foam can also cause wasting of the biomass which leads to plant upset and loss of acclimation to some compounds. Anionic surfactants, such as true soap, sulfonated alkyl or alkyl aryl compounds, fall into this category and are biodegradable. Alkyl benzene sulfonate was one of the first artificial detergents and was only recently discontinued when scientists pointed out how difficult to degrade it was and how severe its impact on the environment was. Linear surfactants will biodegrade completely. Non-ionic surfactants such as, alcohol ethoxylates and alkyl phenol ethoxylates, can be degraded by an acclimated biomass. Cationic surfactants, such as quaternary ammonium compounds, can be toxic in moderate to high concentrations. Cationic surfactants are employed in the textile industry as anti-static agents, emulsion stabilizers, polyester scours, general machine cleaners, and as a leveling agent for polyacrylic dyeing. |
| Alken Clear-Flo® 7004 is effective against most detergents, including nonylphenols, ethoxylated and alkoxylated alcohols (linear or branched), sulfonated benzene or xylene, . When foaming is caused by Nocardia, foam can be immediately controlled and floccing restored by application of 10 ppm (mg/L) to 20 ppm (mg/L) dosage of Alken Nu-Bind. 1 In cold weather, CF 7004 can be mixed 50-50 with Alken Clear-Flo 7018, which also degrades phenolics in the wastewater, just as CF 7002, mentioned above, does, in warmer temperatures. |
