Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 1 OF 8

Transcription

1 Health and Social Services Environmental Health Services Guidelines for Greywater Disposal at Remote Camps INTRODUCTION The provision of safe methods of sewage disposal at remote camps can often be challenging, particularly with constraints such as steep topography, remoteness and subsoil conditions such as permafrost or bedrock. These guidelines are intended to assist operators at remote, seasonal camps in selecting an alternate and practical method for on-site disposal of greywater wastes. These guidelines apply only to seasonal camps where all human wastes are disposed of using pit privies, incinerating toilets or composting toilets and are seasonal, with a camp size up to 49 persons. In such cases, greywater is the only liquid sewage requiring on-site disposal. The guidelines allow for disposal of the greywater using systems other than the conventional methods required for camps with flush toilets (i.e. septic system). The objectives are to ensure that the greywater is disposed of in a safe manner that minimizes public health and safety concerns and also minimizes environmental disturbance and potential problems associated with wildlife interactions. For the purposes of these guidelines, the following definitions apply: Greywater: Wastewater from a sink, shower, bath, laundry or other domestic source but does not include human waste. Human Waste: Human excrement and urine, often referred to as black water. Seasonal Camp: A camp which operates for a limited time each year during the summer months only (i.e. Spring through Fall). These guidelines offer two methods for disposal that can be pre-designed. One method is for small camps with nonpressurized water systems and the second type is appropriate for larger camps which have pressurized or gravity-feed water systems with higher water consumption. The designs described herein can be approved under the Sewage Disposal Systems Regulation O.I.C. 1999/82. Any other designs must be designed and sealed by a professional engineer registered in the Yukon who has appropriate knowledge and experience. DESIGN GUIDELINES Greywater typically contains organic material from food wastes generated from the kitchen as well as nutrients, soaps, organics and waste materials collected from bathing, laundry and sinks. Under the Sewage Disposal Systems Regulation, sewage is defined as waste water, human sullage or waste of a like nature contained in or discharging from kitchen, bathing, toilet, laundry facilities or other similar facilities or a privy. As such, greywater is considered sewage and requires a certain level of treatment and control to minimize problems with public health, environment and wildlife. As such, it must be treated to remove waste materials prior to disposal into the environment. The concept for an acceptable treatment and disposal method for greywater includes a settling tank followed by filtering to remove a large portion of remaining solids with final discharge of the effluent into a contained lagoon or subsurface disposal system. For small camps using minimal amounts of water, a simpler method using filtering and direct disposal into the ground may be acceptable using a barrel system as described in this document. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 1 OF 8

2 The following separation distances and requirements apply to any greywater treatment and disposal system: The greywater disposal site must be at least 30 m from any surface water. There can be no direct discharge, overland flow or other direct connection of greywater effluent to surface waters or groundwater. The greywater disposal site must be at least 30 m from any water source used for drinking water in the camp. The receiving soils at the disposal site must be in a thawed state to accept greywater effluent. For systems that are plumbed, the kitchen should be equipped with a properly sized and maintained grease trap. Unauthorized persons must be restricted from accessing the surface discharge location of the effluent by means of signage, remote location, fencing, etc. Where there are wildlife concerns, the disposal area may have to be fenced or other suitable controls provided. There are two types of systems that can be used for treating and disposing of greywater. The method selected depends on the volume of greywater produced and also whether the system is pressurized or not. For design purposes, the volume of greywater that is produced each day can be estimated from the following table and can be used to determine which system is appropriate. TABLE 1 Water System 1. Non-pressurized system, typically self-haul, where greywater is generated only from water used for cooking and dishwashing 2. Pressurized system where water is used for cooking, dishwashing, bathing, and general cleaning 3. Pressurized system where water is used for cooking, dishwashing, bathing, general cleaning plus laundry Daily Volume of Greywater 14 litres/person (3 Igal./person) 90 litres/person (20 Igal./person) 115 litres/person (25 Igal./person) The number of people per day is the maximum number of individuals that can be expected at the camp, including operators, owners, staff and visitors, at any time. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 2 OF 8

3 Option 1: Greywater Barrel System For a non-pressurized system, where daily volumes of greywater are relatively low, a simple treatment and disposal system using a drum or barrel may be used. The main features of the barrel system are shown in Figure 1 and generally consist of a geotextile filter fabric fastened over the open top end of the barrel, which is filled with graded gravels and sand. The bottom end of the barrel is perforated to allow filtered greywater to be discharged below grade through granular soils. Greywater is poured by hand through the upper filter and is filtered through sands and gravel before it enters the ground. The separation distance and requirements outlined earlier must be adhered to. Operational requirements are as follows: The daily volume of greywater per day that can be treated per barrel is 25 Igal. The camp must have enough barrel systems to accommodate the demand of the camp population. The barrel must be protected from rain and snow. There should be at least 2 m (6 ft.) of separation between barrels. The solids collected in the top filter in the barrel must be disposed of by burial or burning. An extra filter must be maintained on hand for replacement when required. Option 2: Greywater Septic System For systems in which the daily maximum volume of greywater exceeds 227 litres (50 gallons) and/or systems which are pressurized, pre-treatment and disposal requirements will be similar in many respects to a conventional on-site system as per the Design Specifications for Sewage Disposal Systems as provided by Environmental Health, YG. However, some of the requirements have been relaxed to some extent in order to make the design more appropriate for greywater disposal. They are outlined as follows: Pre-treatment is required, consisting of settling chamber and filter. The settling chamber must be sized to provide at least 12 hours of settling based on the estimated maximum daily flow. The settling tank must conform to the requirements specified in CSA B66 Design, material and manufacturing requirements for pre-fabricated septic tanks and sewage holding tanks. The tank does not necessarily need to have CSA certification, but must conform to the general requirements as laid out in the standard, including Materials (i.e. fibreglass, steel, concrete or polyethylene) Strength, watertightness and corrosion resistance Inlet and outlet connections and devices Access openings as may be required for controls and pump-out The filter must be sized according to the daily flow rate and be capable of removing solids larger than 0.8 mm (1/32 ). Options include an effluent filter, similar to those used in septic tanks, to prevent carryover of solids into the drainfield. An acceptable product includes those provided by Polylok Inc. Final disposal of the effluent from the tank can be piped by gravity or pumped from the settling tank to a final disposal area. Acceptable methods of disposal include the following: a) Conventional On-site System A conventional in-ground system using perforated piping or chambers can be used following the Design Specifications for Sewage Disposal Systems as provided by Environmental Health Services, except that the application rate of liquid to the receiving soil may be increased as outlined in the following table. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 3 OF 8

4 TABLE 2 Soil Type Gal./Day/Ft.² L/Day/m² Coarse sand and gravels Silty sand or silty gravel Silt, silty loam, clay loam In addition to the above, the following must be adhered to: 600 mm (2 ft.) min. earth cover over piping in an in-ground system 600 mm (2 ft.) min. separation from the base of the drainfield system to the seasonally high water table, bedrock or impermeable soils Provide a 600 mm (2 ft.) thick layer of filter sand below the drainfield where gravels or cobbles are encountered, or where suitable receiving soils must be provided in order to satisfy separation requirements. b) Sewage Lagoon An excavated lagoon may also be an acceptable disposal method, relying on exfiltration for disposal into the underlying soils plus evaporation, provided it meets the separation requirements. The disposal site must not have a ground slope greater than 10% and must be designed to restrict escape of liquids from the containment area. The site should be cleared and levelled to expose the receiving soils and the lagoon constructed to a depth of at least 1 m (3 ft.) to provide storage capacity for excessive rainfall events and peak flows. Berms should be constructed to at least 0.6 m (2 ft.) above the surrounding grade and be impermeable to restrict surface water from entering the lagoon. A typical lagoon berm section is provided in Figure 2. It is recommended that the drain line to the lagoon be at least 100 mm (4") dia. and if as a gravity line, should have a minimum slope of 1%. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 4 OF 8

5 DESIGN PROCEDURES The following outlines the steps required to design the greywater septic system: STEP 1 Determine the maximum number of persons in your camp at any time. STEP 2 Estimate the maximum daily volume of greywater produced using Table 1. STEP 3 STEP 4 STEP 5 Determine the settling tank size and specifications (i.e. min. 12 hr. retention). Determine the effluent filter requirements based on daily volume and filter size requirements. Select the location and type of soil absorption system. Considerations include soils types, conditions, topography, and separation distance requirements. STEP 6 Determine the size of the absorption system based on Table 2. STEP 7 Apply for a permit so the system can be installed. Example: 30-person camp, fully plumbed system with laundry facilities Soils: silty sand, bedrock at 1.8 m (6 ) below grade Topography: less than 10% slope STEP 1: Maximum no. of persons = 30 STEP 2: Maximum daily volume of greywater: 30 x 115 litres/person/day = 3,450 litres/day (760 Igpd.) STEP 3: Settling tank volume required: 3,450 x ½ (i.e. 12-hr. retention) = 1,725 litres (380 Igal.) Select a 2,273 L (500 gal.) fibreglass septic tank meeting CSA B66 requirements. STEP 4: Effluent filter: Select a filter with openings 0.8 mm (1/32 ) and rated for at least 3,450 litres/day (760 Igpd.) STEP 5: Choose type and location of disposal system: Given that the site is relatively level, with soils of silty sand, an in-ground system or a lagoon could be used. In order to satisfy separation distance requirements as well as other constraints, the camp location should be selected based on the suitability for an appropriate greywater disposal method and site. For this example, we will assume that a suitable site is available on site and that either a soil absorption system or a lagoon will be appropriate. STEP 6: Sizing the system: The absorption area required = 3,450 L/day = 75 L/day/m² * = 46.5 m² (500 ft.²) * Based on soils rating from Table 2. If a drainfield is selected for disposal, it may be an absorption bed or shallow trench system having a total basal area of 46.5 m² (500 ft²). Other design features shall be as per the Design Specifications for Sewage Disposal Systems as provided by Environmental Health Services. Being in a remote location, a gravel-less system using chambers would probably be appropriate to use. If trenches are used, it is suggested that their length be limited to 12 m (40 ft.) for better performance. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 5 OF 8

6 If a lagoon is selected as a disposal method, it would be sized at 7 m x 7 m (23 ft. x 23 ft.). Berms must be constructed of silty non-organic material, well compacted, with side slopes at 2:1. The berms must be made impermeable to restrict surface liquid from entering or escaping from the lagoon. STEP 7: Apply for a permit as per the following. APPLICATION AND PERMITTING A permit must be obtained from Environmental Health Services, prior to installing a greywater disposal system at the camp. The submission must include the application for a Permit to Install a Sewage Disposal System, along with the following: Map showing camp location topo map at 1:50,000 Site plan showing camp, pre-treatment system, disposal system and distances from the disposal area to surface water bodies, camp and drinking water source Maximum number of persons in camp Camp time frame Water source and description Pressurized or non-pressurized water system Information on soils and topography (i.e. soil type, depth to bedrock, topographic features, etc.) Design details of proposed treatment and disposal system (as per above design procedures) After the permit has been received, the construction of the greywater septic system can begin. Following is a list of photographs that must be taken during construction and submitted to EHS for documentation purposes within 30 days of the installation and prior to using the new system: 1. For greywater barrel system, provide photos showing the following: Excavation for greywater barrel Various layers of granular material as the barrel is filled Final installation with filter and lid Location of barrel relative to surroundings and camp 2. For conventional on-site system using in-ground soil absorption, provide photos showing the following: Excavation containing settling tank and bedding material Confirmation or certification that the tank meets listed CSA B66 standards Effluent filter Trench between septic tank and in-ground system Excavation for field showing soil profile Excavation showing all of the components in the system, which may include filter sand, drainrock, chambers, piping and geotextile (various photos will be required) Absorption field after backfilling showing cleanouts, observation pipe and relationship of disposal system to the camp Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 6 OF 8

7 3. For conventional on-site system using a greywater lagoon, provide photos showing the following: Excavation containing settling tank and bedding material Confirmation or certification that the tank meets listed CSA B66 standard Effluent filter Excavation of the lagoon showing soil profile Final construction of lagoon with indication (tape measure in photo) of depth and berm height Piping from settling tank to lagoon Final construction showing relationship of lagoon to the camp OPERATION AND MAINTENANCE The disposal area must be located and constructed in such a way as to allow the effluent to exfiltrate into the soils and avoid erosion and damage to vegetation. For the greywater barrel system, the top filter must be cleaned of solids regularly to prevent clogging. Replace the filter material as required. The effluent filters in the greywater septic tank system should be inspected regularly and cleaned once per month or more often as required. When a lagoon is used for disposal, the liquid level must be monitored regularly. At least 0.6 m (2 ) of freeboard distance from liquid level to the top of berm should be maintained at all times. Expand the existing lagoon or build a new one as required. Never allow surface waters to enter the lagoon. When an in-ground system is used for disposal, the monitoring standpipe should be inspected regularly to check for standing liquid within the drainrock or chambers. Standing liquid may indicate a problem and corrective actions may be necessary. Solids from the filters must be disposed of in an approved manner, which can include incineration or removal from the site. At the end of the season, the settling chamber will need to be emptied to prevent freezing damage to the tank. After allowing the contents to settle, the liquid can be discharged into the disposal area and the settled solids should be disposed of into an excavated pit and buried. All lines should be drained to prevent damage from freezing. Low-phosphate laundry and dish detergents are recommended for use in the camp. In a piped system, the kitchen must be equipped with a grease trap which should be regularly inspected and cleaned as required. The camp s greywater should not contain kitchen oil, floating solids or garbage. Restrict access to the disposal site by camp occupants using fencing, remote location, signage, etc. Provide fencing as required to restrict wildlife from entering the disposal area in order to reduce public nuisance and safety concerns. Electric fencing can be an appropriate and effective deterrent for bears. Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 7 OF 8

8 DECOMMISSIONING AND CLEANUP At the completion of camp operations, the greywater treatment and disposal systems must be decommissioned. Acceptable guidelines for decommissioning and clean-up are as follows: Greywater Barrel System Remove the barrel components to off-site disposal. Bury the gravel and sand filter materials and contour the site. Conventional On-site System Pump the contents of the tank into the in-ground system and remove the tank to off-site disposal or re-use. Cut off all monitoring and cleanout pipes in the drainfield to 300 mm (1 ft.) below grade and abandon the remaining system in situ or, if chambers are used, remove for re-use. Blade and contour the disposal site. Lagoon System After allowing time for exfiltration and evaporation of all liquids in the lagoon, the berms should be pushed into the lagoon centre without allowing any escape of liquid and the entire site reclaimed by blading and contouring. For further information, contact: Environmental Health Services #2 Hospital Road, Whitehorse, Yukon Y1A 3H8 Phone (867) Fax (867) Toll-free in Yukon , ext Environmental Health Services ~ Guidelines for Greywater Disposal at Remote Camps ~ MARCH 2012 ~ page 8 OF 8