Wastewater treatment is a process that eliminates contaminants from wastewater so that the water can be safely returned to the environment or reused.  There are different sources of “wastewater” originating from homes, schools, businesses, factories and stormwater runoff that are directed for treatment at an appropriate type of wastewater treatment facility.   For domestic wastewater, also  referred to as municipal wastewater or sewage, the treatment plant is called a sewage treatment facility.  This type of plant is also sometimes called a publicly owned treatment works (POTW). For industrial wastewater, treatment either takes place in a dedicated industrial wastewater treatment, or in a sewage treatment plant, usually after undergoing some form of pre-treatment. Other types of wastewater treatment plants include agricultural wastewater treatment and landfill/leachate waste treatment plants.

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Sewage treatment plants typically incorporate three stages of treatment: preliminary, primary and secondary treatment.  Preliminary treatment consists of screening solids such as leaves, twigs and litter that’s collected and landfilled.  Primary treatment involves directing the wastewater to settling tanks where heavier organic solids like feces and food sink to form primary sludge that is removed and digested.  Other primary treatment methods include chemical coagulation and filtration.  The wastewater then proceeds on to secondary treatment where up to 90% of the remaining organic matter is removed by biological treatment processes involving the combination of aerobic bacteria and other microorganisms, aeration and final settling.  This results in secondary sludge that’s combined with the primary sludge for digestion.  Some of the secondary sludge is returned to the aeration tanks to help maintain the right mix of helpful microorganisms and process incoming wastewater.  The outgoing wastewater is typically treated with sodium hypochlorite for disinfection prior to release as clean water into local waterways.  The combined sludge is further treated by anaerobic microorganism digestion and dewatering, then shipped for landfill or some beneficial use, such as composting.

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Processes commonly used in industrial wastewater treatment include phase separation (sedimentation, oil-water separation), biological and chemical oxidation, and polishing (chemical neutralization/pH adjustment, carbon filtration, ion-exchange). After treatment, the treated wastewater may be reused or released to the sanitary sewer or to some surface water in the environment. 

 

Regulation

In the United States, wastewater discharges to the environment are regulated by the Environmental Protection Agency (EPA) under the Clean Water Act. The EPA has established wastewater discharge standards as national effluent guidelines on an industry-by-industry basis.  These are technology-based regulations intended to achieve the greatest pollutant reductions that are economically achievable for an industry.  The standards for direct dischargers to surface waters, such as sewage treatment plants (POTWs), are incorporated into National Pollutant Discharge Elimination System (NPDES) permits issued by States and EPA regional offices.  Permits or other control mechanisms for indirect dischargers to POTWs are issued under to the NPDES Pretreatment Program. In addition, non-regulatory organizations such as the National Sanitation Foundation (NSF) and the American National Standards Institute (ANSI) develop and offer guidelines for wastewater treatment.

 

Biohazards

Biohazards, or biological hazards, can adversely affect human health in a variety of ways and can be pathogenic, sensitizing or toxic. Biohazards include microorganisms, such as bacteria, viruses and fungi, toxic byproducts, and biological materials, such as blood, feces and urine. The severity of biohazards can range from relatively mild illnesses and allergic reactions to serious medical conditions, including death.

 

Garment Selection Criteria

The personal protective equipment (PPE) selection process, including for protective garments, must always begin with completing a comprehensive hazard risk assessment.  When biohazards are an identified risk, what ones may be present and their potential to contact the garment and other PPE must be determined. This can be done by establishing the exposure scenario by answering a series of questions:

• Where on the body may there be contact?

• What will be the concentration and intensity of the contact?

• What quantity of material is involved?

• What is the duration and frequency of contact?

 

Answers to these questions will help to select the garment material and design that provides the required level of protection based on the exposure scenario. 

 

If additional hazards, such as chemicals, are present, they also need to be factored into the exposure scenario and selection process.

 

For DuPont offerings, please refer to the following brochure on biohazards.

• Tyvek® 400 coveralls can be considered for dirty job work and dry particulate hazards of 1micron or above, and applications where garment durability is critical.   

• Tyvek® 600 coveralls (with blue taped seams) have a dual use, protection against biohazards and common cleaning and disinfection chemicals.  It protects against sodium hydroxide (50%) bleach (15%) and sulfuric acid (30%) and other low concentration inorganic chemical solutions.    It meets ISO 16603: resistance to blood and bodily fluid.

• Tyvek® 800 coveralls (with orange taped seams) are good for liquid spray protection, even in pressurized form, and meets ISO 16604: Resistance to bloodborne pathogens.  

• Tychem® 2000 fabrics with taped seams have been tested and have passed the requirements of ASTM Standards F1670 and ASTM F1671, the recognized blood and viral penetration test methods in North America

ProShield® 70 Boot & Shoe Covers also meet ASTM F1670 and ASTM F1671 for resistance to bloodborne pathogens and is fluid impermeable.