On-site Wastewater Systems Public Health Overview

Transcription

1 On-site Wastewater Systems Public Health Overview

2 Overview of Presentation

3 Definitions Sewage: can be described as the waste from day-to-day living of people, or the human excreta, or the water-carried waste from drinking, bathing, laundering, or food processing. Wastewater; means the composite of liquid and water-carried wastes associated with the use of water for drinking, cooking, cleaning, washing, hygiene, sanitation, or other domestic purposes and includes greywater but does not include liquid waste from industrial processes (Alberta Private Sewage Systems Standard of Practice 2009)

4 Definitions Effluent: means the liquid discharged from any on-site wastewater treatment system component

5 What is in Wastewater? Sources of Sewage Human Wastes Animal Wastes Household Wastes Street Washings and Storm Flows Industrial Wastes

6 What is in Wastewater? Wastewater is about 99% water and 1% trace contaminants Typical components: organics, total suspended solids, nutrients, pathogens, fats, oils and grease. Biochemical Oxygen Demand (BOD) and Total Suspended Soilds (TSS) are used to measure the strength of wastewater. Excessive nutrients can have an impact on nearby water bodies phosphorus making its way into surface water can cause algae blooms; some algae can release toxins nitrates that enter drinking water sources can have health effects, especially for babies (blue baby syndrome) Fats, oils, and grease can plug-up or clog treatment components

7 Pathogens in Wastewater Viruses: Viruses are microbes that reproduce only within the cells of another organism. Hepatitis A is an example of a virus which is commonly found in wastewater. Bacteria: E. coli is a common organism used to monitor for fecal contamination of water supplies. Bacteria have the potential to cause intestinal infections such as gastroenteritis (stomach upset) and dysentery (diarrhea). Protozoans: Intestinal parasites that are protozoans exist as onecelled organisms or as a cyst, a hard, protective covering. Examples include Giardia lamblia and Cryptosporidium parvum. Worms: Helminths are parasitic worms (roundworms and tapeworms)

8 Hazards or Problems Associated with Wastewater Undesirable bacteria and viruses (pathogens) Odours Impact on receiving streams and groundwater Nuisance animals and bird attraction Unsightly conditions Increased level of water treatment required for downstream users

9 Why Do We Treat Wastewater? Sewage contains chemical and biological constituents that can cause environmental and public health problems or nuisances if the waste is not safely treated and disposed. Of particular importance is the treatment and safe disposal of sewage to prevent contamination of food or water and to prevent the incidence and transmission of disease Safety Codes Council and Alberta Municipal Affairs, 1999.

10 How is Wastewater Treated? There are two common groups of components in onsite wastewater treatment systems: Initial Treatment Components Final Treatment Components

11 How is Wastwater Treated? Initial Treatment Components Any tank, including septic tank, or system that provides primary (and sometimes secondary) treatment of wastewater prior to the final treatment component Most common initial treatment component is the septic tank which provides primary treatment; the physical separation of gross settleable solids Septic tanks typically consist of two chambers Solids, grease, and other settleable or floatable materials are retained in the primary chamber Partially treated liquid (effluent) is allowed to flow to a second chamber for further treatment to the final treatment component

12 Initial Treatment Components Septic Tank Light material will float creating a scum layer Heavier material will sink creating a sludge layer

13 Package Treatment Plants An initial treatment component that produces a higher quality effluent Similar to a Septic Tank but have some some advanced treatment: Aeration Filtration Various Manufacturers

14 Packaged Sewage Treatment Plants Aerobic treatment plants that use various methods, depending on their design, to expose the sewage to oxygen. Increased levels of oxygen in the sewage provides for the establishment of large aerobic bacteria populations. Aerobic bacteria populations accelerate the decomposition of the suspended solids in sewage

15 How is Wastewater Treated? Final Treatment Component Includes treatment fields and sand treatment mounds where the effluent infiltrates into the soil Relies on nature to operate Uses the soils naturally occurring microorganisms and physical and chemical process in the soil to further treat the sewage effluent in order to prevent pollution and subsequent public health hazards

16 How is Wastewater Treated? Final Treatment Component As soil is relied on to complete treatment and absorb the effluent it is one of the most critical parts of any onsite wastewater treatment system An understanding of soils is necessary in onsite design

17 Where Does the Water Go in an Onsite System? Over 90 % goes DOWN Thus an understanding of the soil receiving effluent in an onsite wastewater system is important.

18 Soil Characteristics The soil can act as a filter and remove suspended particles The degree of filtration depends on the characteristics of the soil

19 Soil Characteristics Soil characteristics that will have the largest impact on the movement of water Soil Texture the feel of a soil; percentage of sand, silt, and clay in the soil Soil Structure- how the soil is formed in clumps, leaving small cracks in the soil for water to move through Example Difference between dealing with a sandy soil verses a heavy clay

20 Soil Texture Soil Structure

21 Soil Treatment The soil is relied on to further treat wastewater Aerobic and anaerobic conditions exist within soil Aerobic bacteria are the most efficient bacteria at using organic materials for growth and reproduction

22 Soil Treatment

23 Treatment Fields Probably the most common final treatment method Disperse effluent into the soil by either a distribution header or box with numerous subsurface trenches The soil treats the wastewater by degrading or consuming the contaminants. Disposal Field Installation Using A Deep Bury Pump Type Septic Tank (Other designs may also be acceptable) Fig.Typical DF 1

24 Treatment Mounds Due to site (soil) restrictions, proper treatment of the sewage effluent is not possible under "natural" conditions with effluent from a septic tank and disposal field Construction of a treatment mound may be a viable method of effluent treatment and disposal.

25 Open Discharge Due care and consideration must be exercised when proposing this type of system. Open discharge systems are simply a means whereby effluent from the septic tank is discharged directly onto the ground surface.

26 Concerns About Open Discharge System Although an open discharge system may be one of the most economical methods of treatment and disposal of effluent, it is also the least desirable. Health, environmental and nuisance concerns often become a major issue with this type of system. It is strongly recommended that the area wetted by the open discharge system be fenced to keep animals and children away. Exposure to children and animals Attracts insects and animals Contaminates surface and ground water Produces offensive odour

27 Open Discharge Systems Are No Longer Approved by Health Canada Because of the risks to health and the environment, open discharge sewage systems will not be recommended or approved by Health Canada, effective July 1, 2002, due to the following reasons: Sewage effluent disposed on the ground surface is accessible to children, pets and pests. This presents serious health hazards because sewage contains disease causing germs such as bacteria, viruses and parasites. In a number of disease outbreak investigations, open discharge sewage disposal systems have been associated with the spread of diseases such as Shigellosis and Hepatitis A. Infants, children and elderly are especially vulnerable to these illnesses as their immune systems are weak. The sewage effluent discharged onto the ground can destroy the surrounding environment and contaminate drinking water supplies and natural resources such as fish.

28 What happens with improperly managed wastewater?

29 What happens with improperly managed wastewater?

30 Common Causes of Sewage Back-Up into the House Obstruction of the Sewage Line Septic Tank/Components not Functioning Sewage Line Frozen Damaged Sewage Line Absence of Back Flow Preventer Lack of Maintenance and Service of Septic Tank

31 Health Concerns Associated with Sewage Back-Ups Exposure to potentially harmful sewer gases Odour Exposure to disease causing organisms (Pathogens) Damages furnace, water heater and other appliances Damages walls and insulation Produces fungus and other organisms Contaminates foods and other material Affects electrical wires and gas lines

32 Efficient Operation of a Private Sewage Disposal System 1. Do not permit roof water, storm water, surface water or foundation drainage into the tank or onto the absorption field; 2. Do not allow any vehicular traffic over any part of the disposal system; 3. Do not plant trees with large root systems in the disposal field area;

33 Efficient Operation of a Private Sewage Disposal System 4. Do not add paper towels, newspapers, wrapping or sanitary supplies into the system. They may not decompose or may plug a septic pump; 5. If pools of water are evident on a disposal field area: use less water; consult Health Centre/EHO; 6. Keep a sketch available showing the location of the tank and disposal field with respect to the location of the house, etc.

34 Concerns about Sewage Back-Up Exposure to gases Odour Exposure to disease causing organisms Damages furnace, water heater and other appliances Damages walls and insulation Produces fungus and other organisms Contaminates foods and other material Affects electrical wires and gas lines

35 What To Do When Sewage is Backed-Up Be cautious in entering sewage back-up in basement relative to electric outlets and gasoline line. Do not use toilet, washroom sink, bath tub and kitchen sink. Pump the Septic Tank. Drain the Sewage. If carpet and floor covering are heavily contaminated, discard.

36 What To Do When Sewage is Backed-Up Discard food which had come in contact with sewage Discard perishable foods stored in refrigerator where electricity has been off more than 24 hours. Clothing, upholstered furniture, toys, bedding and other similar items should be discarded unless they are cleaned and disinfected.

37 What To Do When Sewage is Backed-Up Pump out the remaining sewage from the basement. Wash floor with detergent solution then disinfect using chlorine solution (one cap of bleach to one gallon of water). Damaged drywalls and insulation should be discarded. Open windows to circulate the air.

38 Common Causes of Disposal System Failure Improper Site Selection High Water Table Unsuitable Soil Improper Design of Sewage Disposal System Improper Installation Lack of Maintenance

39 What Type of System is This?

40 Consequences of Raw Sewage Ponding on Surface Raw sewage contains several pathogens (disease causing microorganisms) An offensive odour Attract rodents, insects, flies, and animals which may act as vectors of disease Transmission of disease causing microorganisms to humans and animals.

41 Consequences of Raw Sewage Ponding on Surface Potential to cause surface water and ground water contamination (algae growth, nitrates in groundwater) Contamination of vegetables and other foods growing in the garden Chances of children and domestic pets exposed to sewage/effluent

42 QUESTIONS???