Materials Safe for Sewer

What Can Be Sewered? 

Waste disposal would be greatly simplified if all liquid waste could be poured down the drain. However, common sense tells us that some things shouldn't end up in Green Bay. What can or cannot be poured down the drain is regulated by the Green Bay Metropolitan Sewerage District. The METRO Sewerage System must comply with the Clean Water Act and other State and Federal Regulations which limit discharge. Regulations concerning sewer use are found in the Green Bay Metro Sewer Use Ordinance, adopted May, 1993. The material below covers the main points of the ordinance which may apply to campus employees. If you want a copy of the complete ordinance please contact Scott Piontek, ext. 2273.

It is easier to describe what should not be disposed of via the sanitary sewer rather than what is allowed. It is important that a distinction is made between a sanitary sewer and a storm sewer. Storm sewer run-off typically goes directly into the river/bay, therefore it is very important that liquids are not disposed of via a storm sewer. Sanitary sewerage is pre-treated before being discharged into the river/bay. The most current Sewer Use Ordinance specifically prohibits the following from being disposed of via a sanitary sewer:

  1. Very hot (> 150o F) or very cold ( < 32o F) liquids. Generally benchtop quantities of very hot or very cold liquids used in academic laboratories can be poured down the drain since all campus liquids wastes are mixed together and liquid temperatures will moderate before leaving the campus.
  2. Waste which creates a fire hazard (flash point < 140 oF) - check the MSDS or label for this information. Flammable solids and gases should also be excluded from sewerage.
  3. Volatile substances such as gasoline, kerosene, naptha, benzene, toluene, xylene, ethers, alcohols, ketones, aldehydes and peroxides. Benzene concentrations shall not exceed 0.5 mg/L.
  4. Solid or viscous material which is likely to cause obstruction to sewer flow e.g. mud, straw, plastics, wax, wood, animal guts
  5. Liquids with a pH < 5 or > 9. Campus personnel can neutralize acids and bases and then pour down the drain. See comments below on neutralization.
  6. Radioactive wastes which do not comply with the National Pollutant Discharge Elimination System
  7. Petroleum oil, nonbiodegradable cutting oil, or products of mineral origin
  8. Strongly colored solutions
  9. Certain heavy metals as listed below with restrictions on concentration and quantity. If both concentration and quantity amounts are exceeded, liquid waste cannot be sewered:
Metal Concentration
  MG/L Pounds/24 hours
Arsenic 0.5 0.2
Cadmium 2.0 0.8
Chromium (total) 10.0 4.0
Copper (total) 5.0 2.0
Cyanide (total) 5.0 2.0
Mercury 0.02 -
Nickel 10.0 4.0
Zinc 15.0 6.3
Acrylonitrile 1.0 -

Take special note of the low concentration limits for arsenic, lead and mercury and the fact that the concentration of the metal in solution is the only criteria for mercury disposal.

Academic institutions tend to discharge small quantities of a variety of substances as opposed to the industrial discharge of large quantities of a limited number of substances. It is possible that small quantities of one of the above prohibited items may be safely sewered. However, before you do this, contact the UWGB University Safety Manager, Scott Piontek, ext. 2273, who will seek permission from the METRO Sewerage District.

If you accidentally discharge one of the prohibited substances in a sanitary sewer, the campus must notify the METRO Sewerage District. Please contact Scott Piontek, ext. 2273, if this occurs.

Material Which May Be Safely Sewered

  1. alcohols (methyl-, ethyl-, propyl-, isopropyl-, "reagent" alcohol) acetone, and glycerine - If the concentration is less than 24% alcohol by volume benchtop quantities may be flushed down the drain of a chemical sink with 20 volumes of water. However, it is not allowable to dilute alcohol for the purpose of rendering it non-hazardous.
  2. dilute, < 20%, aqueous solutions of potassium chlorate or sodium chlorate
  3. dilute, < 20%, aqueous solutions of the following chemicals
AciAcid, Ascorbic 
Acid, Benzoic 
Acid, Boric 
Acid, Casamind 
Acid, Citric 
Acid, Lactic 
Acid, Oleic 
Acid, Phosphotungstic 
Acid, Phthalic 
Acid, Salicylic 
Acid, Silicic 
Acid, Stearic 
Acid, Succinic 
Acid, Tartaric 
Aluminum Hydroxide 
Aluminum Oxide 
Amino Acids, alpha and salts 
Ammonium Bicarbonate 
Ammonium Carbonate 
Ammonium Chloride 
Ammonium Citrate 
Ammonium Lactate 
Ammonium Sulphamate 
Ammonium Phosphate 
Ammonium Sulfate 
Barium Carbonate 
Beef Extract 
Barium Sulfate 
Buffer Solution 
Calcium Borate
Calcium Chloride
Calcium Carbonate 
Calcium Fluoride 
Calcium Citrate 
Calcium Oxide 
Calcium Lactate 
Calcium Sulfate 
Calcium Phosphate 
Cerelose, Dextrose 
Copper Oxide 
Chromatographic Absorbent 
Cobalt Oxide
Extract, Malt 
Extract, Yeast 
Ferrous Ammonium Sulfate 
Ferric Sulfate 
Gum, Arabic
Iron Oxide 
Litmus, Mild 
Lithium Carbonate 
Lithium Chloride 
Lithium Sulfate 
Magnesium Borate 
Magnesium Citrate 
Magnesium Carbonate 
Magnesium Chloride 
Magnesium Lactate 
Magnesium Oxide
Magnesium Phosphate 
Magnesium Sulfate 
Manganese Acetate 
Manganese Chloride 
Manganese Dioxide 
Manganese Oxide 
Manganese Sulfate 
Methyl Salic ylate
Potassium Acetate 
Potassium Bicarbonate 
Potassium Bisulfate 
Potassium Bitartrate 
Potassium Borate 
Potassium Bromate 
Potassium Bromide 
Potassium Carbonate Potassium Iodide 
Potassium Lactate 
Potassium Phosphate
Potassium Sodium Tartrate 
Potassium Sulfate 
Potassium Sulfite 
Potassium Sulphocyanate 
SDS (sodium dodecyl sulfate) 
Sodium Acetate 
Sodium Ammonium Phosphate Sodium Benzoate 
Sodium Bicarbonate 
Sodium Bisulfate 
Sodium Borate 
Sodium Bromide 
Sodium Carbonate 
Sodium Chloride 
Sodium Citrate 
Sodium Formate 
Sodium Iodide 
Sodium Lactate 
Sodium Phosphate 
Sodium Salicylate 
Sodium Silicate 
Sodium Succinate 
Sodium Sulfate 
Sodium Sulfite 
Sodium Tartrate 
Sodium Thioglycollate 
Sodium Thiosulfate 
Sodium Tungstate 
Strontium Carbonate 
Strontium Phosphate 
Strontium Sulfate 
Sugar alcohols 
Thymol Tin Oxide 
Trypticase Tryptone 
Zinc Oxide