United States Department of Agriculture Planning Guide for Forest Service On-Site Greywater/ Technology & Development Program Wastewater 2300—Recreation Management September 1998 9823 1204—SDTDC Disposal Systems for Recreational and Administrative Sites Part II
v Planning Guide for On-Site Greywater/ Wastewater Disposal Systems for Recreational and Administrative Sites Part II
San Dimas Technology and Development Center San Dimas, California
September 1998
Dave Erlenbach Mechanical Engineering Technician
Paul Lachapelle Research Assistant
Information contained in this document has been developed for the guidance of employees of the Forest Service, USDA, its contractors, and cooperating Federal and State agencies. The Department of Agriculture assumes no responsibility for the interpretation or use of this information by other than its own employees. The use of trade, firm, or corporation names is for the information and convenience of the reader. Such use does not constitute an official evaluation, conclusion, recommendation, endorsement, or approval of any product or service to the exclusion of others that may be suitable.
The United States Department of Agriculture (USDA) prohibits discrimination in its programs on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).
To file a complaint, write the Secretary of Agriculture, U.S. Department of Agriculture,i Washington, DC 20250, or call 1-800-245-630 (voice) or 202-720- 1127 (TDD). USDA is an equal opportunity employer. TABLE OF CONTENTS
PREFACE ...... 1
INTRODUCTION...... 1
PLANNING CONSIDERATIONS...... 1
PLANNING STEPS FOR A WASTEWATER DISPOSAL SYSTEM ...... 2 Site Evaluation ...... 2 Determine Quality of Wastewater to be Treated or Disposed ...... 2 Determine the Characteristics of the Greywater ...... 2 Review Applicable Guidelines for Disposal of Greywater ...... 3 Preliminary Planning Considerations ...... 3 Select a Suitable Option ...... 3
TREATMENT OPTIONS ...... 3 Septic Tank Construction ...... 4 Septic Tank Filter ...... 4 Biofilters ...... 5 Waterloo Synthetic Biofilter ...... 5 Peat Biofilter ...... 5 Aerobic System ...... 6 Rotating Biological Contactor ...... 7 FAST System ...... 8 Singulair Bio-Kinetic Treatment System ...... 9 Whitewater Aerobic Treatment System ...... 9 Nibbler Jr. Wastewater Pretreatment System ...... 10 Bioclere Wastewater Treatment System ...... 10 BioCycle Wastewater Treatment System ...... 11 Recirculating Sand Filter ...... 11 Recirculating Trickling Filter ...... 14 Alternating Intermittent Recirculating Reactor System ...... 14
DISPOSAL OPTIONS ...... 15 Primary Treatment Unit with Alternating Trenches ...... 15 Shallow Trench Low-Pressure Pipe Distribution ...... 16 Contour Disposal Field ...... 17 Gravel-less Trench and Leaching Chambers ...... 19 Pressure Dosed Distribution ...... 19 Artificially Drained System ...... 19 Oversized Distribution Area ...... 21 Electroosmosis System ...... 21 Septic Tank Effluent Pumping System ...... 21 Other Disposal Systems ...... 22 Gravity/Gravel Bed Disposal System ...... 23 Artificial Leaching Chamber ...... 23
iii Low Pressure Piping System ...... 24 Seepage Mound Disposal Method ...... 24 Sprinkler Disposal System ...... 25 Emitter Systems ...... 25
SUMMARY AND CONCLUSIONS ...... 25
RECOMMENDATIONS ...... 26
APPENDIX ...... A-1 Glossary...... A-1 References ...... A-3 Suggested Reading ...... A-5 Other Sources of Information ...... A-5
iv PREFACE The designer must realize the importance of This publication is intended to be used in including maintenance personnel in the preliminary conjunction with the Planning Guide for On-Site processes to ensure consideration is given to the Greywater Disposal Systems for Recreational and installation, maintenance, and operation of the Administrative Sites Publication No. 9523 1201 - system once it is in place. SDTDC April 1995. The two main reasons for presenting new methods As a result of new treatment and disposal methods of wastewater disposal are diminishing supplies developed since the first guide was published, it of good water and rapidly escalating costs of was decided that a second publication detailing treating both potable and/or wastewater. alternative methods was needed. Secondary reasons for disposing of greywater separately include extending the life of the existing wastewater system and rehabilitating an existing The information and data contained in this wastewater system that has already failed because publication are based on actual field experience, of overuse. research, and literature. All the information and technology used in the selection, installation, and operation of a sewage treatment system is The primary objective of this planning guide is to adaptable to the treatment and disposal of assist the designer in obtaining safe and adequate greywater. on-site wastewater treatment facilities and by accomplishing that to: • Minimize the exposure of the public to the Greywater has a different composition than disease transmission potential of domestic combined waste from conventional systems. It is waste entirely free of black waste pollutants and is more • Minimize the potential for contamination of esthetically acceptable for on-site treatment. Also, drinking water supplies and hazards to it is far more economical to process in terms of recreational areas equipment and space required. The examples included are meant to acquaint Forest Service • Reduce the potential for surface and groundwater pollution. personnel with acceptable alternative methods of wastewater treatment and are not intended to provide definitive design information. The PLANNING CONSIDERATIONS treatment devices/methods described must be One of the problems in wastewater treatment and sized to the parameters for each particular site. disposal is the public’s perception of wastewater. Finally, all plans and specifications must be The public regards any water that has been approved by the appropriate agencies, and through a sewer pipe or subjected to some adherence to codes is obligatory. contamination as though its molecular structure has been degraded. An effective way to deal with INTRODUCTION the public’s misconception is to separate or eliminate toilet waste from the main volume of the This publication is intended to help the Recreation wastewater. One area of water conservation that planner/designer. It lists the logical decisions that is often overlooked is the potential for reuse of must be explored before constructing or renovating water on-site. For example, in the typical a campground or an administrative site wastewater administrative site, approximately 34 percent of the facility. Also, it describes some of the newer water consumed is used in flushing of toilets. The methods of greywater/wastewater treatment that remaining 66 percent of the water can be may be used at Forest Service sites.
1 recovered for reuse by on-site wastewater natural moisture regime. Soil texture, structure and treatment and recycling systems and used for consistence relate to the wastewater infiltration landscape irrigation and flushing of toilets and system loading rate or sizing. Where is the ground urinals. Whether disposed of to the soil or to the water? Who else is affected by a sub-surface surface, wastewater will need to be treated disposal field? What watersheds would be according to its eventual reuse, including possibly effected? What potable water sources are for drinking. downstream? How far?
It will be necessary, with some of the more visible Determine Quality of Wastewater to be methods of wastewater treatment, to include the Treated or Disposed public along with Federal, State, local agencies, Look at the design to determine the number of and various environmental groups in the sites, the population-at-one-time (PAOT), and the conceptual design phase. Be advised that it is number and type of fixtures to be installed. Check extremely important to include the public in the with the Forest and/or District to see if plans for planning group as mentioned above, since they expansion will be forthcoming. Plan for additional may have some preconceived notions that are people anyway! Be sure to insist on the use of difficult to unseat. water conserving types of low-flow toilets, faucet flow restrictors, low-flow hose bibs, and low-flow Many Forest Service wastewater problems require shower heads. Use the Uniform Plumbing Code innovative, creative, and cooperative solutions. A and the Forest Service Handbook (FSH 7409.11, positive working environment is needed with water Chapter 50) to size the system. agencies, legislators, regulators, environ- mentalists, and the public. Together, new issues Determine the Characteristics of the can be resolved by using new technologies and Greywater innovative approaches to water resources Campground visitors will generally use throw-away management. plates and cutlery so greywater generation from washing plates, spoons, and forks will be minimal. PLANNING OPTIONS FOR A However, cooking utensils will be washed. Also, WASTEWATER DISPOSAL SYSTEM visitors are likely to pour cooking oil and grease The planning options discussed in this section can (animal fat) into the greywater collection system, be used in any order. once installed, making the concentration of grease and oil comparable with greywater from a restaurant kitchen sink. Because of low usage of Site Evaluation water at the campsites, the concentration of grease Determine if the design can be accomplished at in the campground greywater is expected to be the proposed site. Look at the topography to even higher than restaurant greywater. determine drainage and severe slope areas. Is there any surface water? What are the soil characteristics? Soil is difficult to describe. It is The following table gives the average even more difficult to interpret the meaning of the characteristics of restaurant greywater for descriptions for onsite wastewater treatment estimating purposes. The true character of systems. Four characteristics can provide a pollutant concentrations can only be determined majority of the information needed to make through laboratory testing. interpretations. Soil color often relates to the
2 Table 1. Average concentrations (mg/L) of pollutants.
Pollutant Kitchen Chemical Oxygen Demand (COD) 1400 mg/L Five-Day Biochemical Oxygen Demand (BOD3) 700 mg/L Nitrogen compounds (NO3-N,NH3-N) 5 mg/L Inorganic Phosphate (PO4) 10 mg/L Suspended Solids 500 mg/L Grease 750 mg/L
Review Applicable Guidelines for Select a Suitable Option Disposal of Greywater Select a wastewater system that: Most states require that greywater and blackwater (sewage) be handled in the same fashion as far • Meets the site requirement and the as treatment and disposal are concerned. (Some wastewater quality and characteristics to be revisions to this policy were discussed in the treated and disposed of previous publication.) Federal, State, and local codes and regulations regarding the collection, storage, treatment, and disposal of wastewater • Is simple and dependable must also be followed. Some states now require that wastewater treatment system designers be • Minimizes the need for special skills to operate either a licensed sanitary engineer or have passed a state certification test. • Is reasonable in cost to construct and maintain
Preliminary Planning Considerations • Complies with rules and regulations of Federal, How much land area is available for wastewater State, and local agencies treatment? Are climatic conditions acceptable for the type of system selected? Is there power • Is environmentally benign. available? Is there a sufficient quantity of water available at a high enough pressure? Is the The following information is divided into two areas, campground or facility existing or only in the treatment options and disposal options. Any of the planning stages? Does the collection system need treatment options can be used with any of the to be replaced? What ecological considerations disposal options. How you utilize the two options must be addressed? Of the wastewater treatment together depends on the site specific conditions. alternatives addressed later in this publication, which one would provide the best choice for a particular site, at the lowest cost (both construction TREATMENT OPTIONS and maintenance/operation). All facilities should The purpose of a treatment component is to be designed for use by people with disabilities. transform the in-flowing raw wastewater into an effluent suited to the disposal component, thereby
3 allowing the wastewater to be disposed of in grease carryover and subsequent maintenance conformance with public health and environmental and pollution problems. In an effluent sewer, leaky regulations. For example, in a subsurface soil tanks are unacceptable. absorption system, the pretreatment unit (e.g., septic tank) should remove nearly all settleable Septic Tank Filter solids and floatable grease and scum so that a reasonably clear liquid is discharged into the soil A septic tank filter (figure1) functions as a way to absorption field. This allows the field to operate retain solids in the septic tank, improving the quality more efficiently. Likewise, for a surface discharge of the effluent and reducing the risk of clogging in system, the treatment unit should produce an lateral drainage pipes. The use of a septic tank effluent that meets applicable surface discharge filter can extend the life of the sub-surface requirements. absorption field. The filter is located within the outlet tee of the septic tank. The filter consists of a series of plastic mesh screens within a PVC housing. Septic Tank Construction These finely spaced screens catch larger particle Every user location should be retrofitted with a new matter before it can escape the tank. The screens tank, including those who have a tank in place from also provide a surface area on which an existing septic system. The arguments for new microorganisms can grow which in turn break down tanks are compelling. The preponderance of septic effluent into basic elements and compounds. tanks sold in the U.S. are structurally unsound and almost never watertight. Where groundwater levels The filters can effectively lower Total Suspended are high, leaky tanks allow infiltration that can Solids (TSS) of the septic tank effluent and overburden a system’s pumps and treatment consequently lower the biochemical oxygen facilities. Where high ground water is not a demand (BOD) of the sub-surface media. Today, problem, leaky tanks ex-filtrate and the scum layer there are only a select group of manufacturers who lowers to the discharge ports, causing solids and produce this type of septic tank filter.
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Figure 1—Diagram of a septic tank filter.
4 Biofilters The wastewater is pumped from a septic tank into Aerobic biologically active filters are collectively the insulated enclosure containing the biofilter. called biofilters. Systems utilizing biofilters can be The wastewater is sprayed onto the surface of the a viable alternative at sites to retrofit or repair failed biofilter where it is absorbed and treated by systems. A single pass aerobic biofilter is designed colonies of organisms. Air is drawn around the for efficient and cost-effective treatment of saturated foam media by natural convection or by domestic and municipal wastewater. a small fan. The treated water can then be pump- dosed into a pressurized shallow trench or gravity- fed into a tile bed or leaching field. Presently, the TM Waterloo Biofilter filter is operating in systems that accommodate The biofilter (figure 2) is completely contained in 7,900 gallons per day. the small transportable insulated box which is generally no larger than the septic tank itself. Peat Biofilter Because this synthetic filter uses a medium that can be operated independently of external These systems incorporate a conventional septic environmental conditions, the system will work well tank, a pumping chamber or sump pump with a under any soil or disposal conditions. The biofilter one-horse-power submersible pump and four is the equivalent of a single pass sand-filter, but polyethylene modules containing biofibrous peat the loading rate is 10 times higher in the biofilter. (figure 3). The peat media acts like a condensed drainfield. Biological purification occurs in the media. The effluent percolates through the media and out of the modules by way of perforations in the base. The treated effluent then passes through broken stone placed beneath the system and into
the soil.