© 2006 by Taylor & Francis Group, LLC 137 chapter five Effluent dispersal and recycling systems Introduction All onsite wastewater treatment systems need a mechanism for treated efflu- ent to be dispersed and returned to the hydrologic cycle. Subsurface dis- persal (nonpoint source discharge) is the primary mechanism used for releas- ing effluent from onsite treatment systems. For most of the 20th century, onsite wastewater options were limited to only septic systems, so the choice for wastewater management was either sewer or septic. One of the unin- tended adverse impacts of having limited onsite wastewater choices is deval- uation, or even condemnation, of tracks of land for development when traditional municipal sewer systems are not accessible and soil and site conditions do not meet the regulatory requirements for septic systems. It is widely believed that the rules governing the operation of septic systems are used as de facto zoning tools, mainly because if land is deemed unsuitable for installing a septic system (i.e., no perc), then no one can build a home or any other structure on it that has potential to generate wastewater. Research conducted and field experience obtained over the past several decades indicate that soil and site conditions necessary for treatment and ultimate dispersal of septic tank effluent are not necessary for the treatment and ultimate dispersal of secondary or better quality effluent. Hence, we need to look at soil and site conditions in a totally different manner when advanced onsite wastewater systems are considered and soil and plant sys- tems are used mainly for “polishing” secondary or better quality effluent rather than for reduction of organic waste load. This is the concept mentioned demand (BOD) or total suspended solids (TSS) and does not serve as a medium for mineralization of nitrogen from organic to inorganic forms. Instead, those functions are performed by an advanced treatment system for which the conditions and the material of construction can be controlled, leaving soil to be used for what soil is best for — recycling residual nutrients and polishing the microbiological quality of effluent. in Chapter 1 in which soil is not required to remove biological oxygen © 2006 by Taylor & Francis Group, LLC 138 Advanced onsite wastewater systems technologies Alternatives to conventional septic systems are needed in areas where soil and site conditions are not suitable for treating septic tank effluent or when use of septic systems is not cost effective or not desired, or where desired lot density cannot be achieved by using traditional septic systems. Such systems can also be used for rejuvenating septic tank effluent drain fields that are failing due to age and accumulated biomat. Introduction of aerobic effluent into an old drain field breaks down the biomat and allows the assimilation of aerobic effluent into the subsurface environment, thus in some cases, offering an effective and efficient repair option for old septic systems. Dispersal of advanced secondary effluent Aerobic treatment of wastewater to secondary or better quality effluent should be a key component of any permanent managed onsite wastewater infrastructure. Subsurface dispersal of secondary effluent can be achieved in an environmentally sound manner on any buildable site that is currently viewed as unsuitable for a septic system, as long as adequate land area is available for hydraulic assimilation of the secondary or better quality effluent and reduction in nutrient or bacteriological contaminant load. Because a secondary treatment system reduces organic waste load (typ- ically measured as BOD 5 ; TSS; and fat, oils and grease [FOG]) prior to introducing the effluent to the soil dispersal system, performance of an effluent dispersal system for secondary or better quality effluent is not influenced by biomat formation. In traditional septic systems, the formation of a biomat in the drain field is considered an important part of the treatment for removal and reduction of bacteriological contaminants. Therefore, a question typically arises among regulators about what happens to those contaminants when a biomat is not formed in the dispersal systems that receive secondary or better quality effluent. Dispersal of aerobic effluent into a subsurface soil environment allows the soil to retain aerobic condi- tions (unlike the dispersal of septic tank effluent) and thus enhances removal (neutralization) of bacteriological contaminants even without the formation of a biomat. Whenever necessary, aerobically treated effluent can be disinfected using a variety of advanced onsite disinfection technologies, such as ultraviolet or ozone disinfection systems. When chlorination sys- tems are used, effluent should be dechlorinated prior to subsurface dispersal mainly to prevent any adverse impact of the residual chlorine on soil micro- organisms. Effluent dispersal technologies Technologies available for dispersal of secondary or better quality effluent can be grouped as follows: © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 139 • trenches or beds filled with gravel or other media (gravity fed or pressure dosed) • gravelless trenches or beds with chamber systems (gravity fed or pressure dosed) • at-grade or above-grade (shallow trench, filter bed, mound, capping fill, etc.) • drip dispersal (subsurface or surface) • spray dispersal (above ground) • minimum or zero discharge (evapotranspiration or greenhouse) • point source discharge into surface water or on the ground • existing onsite dispersal systems after removal of accumulated waste- water from them. dispersal systems. Information on many other projects that use such dis- persal systems is available on our web site. Designing, sizing, and layout of these types of effluent dispersal systems can be done using common sense understanding of soil and site conditions and the owners’ requirements. Adequately treated effluent can be safely released into the environment using any of the above effluent management systems, including existing onsite disposal systems (such as cesspools, trenches, seepage pits, infiltration galleries, or beds) that are failing due to excessive build up of a biomat. Highly treated effluent can also be used for flushing toilets or other nonpo- table applications prior to release into the environment, thereby reducing the net amount of liquid discharge. Since septic systems depend mainly on soil for the treatment of primary effluent, soil evaluation has been an integral part of the onsite wastewater business. However, with the availability of a variety of treatment systems, we no longer need to depend on soil for treating septic tank effluent. The installation of small, shallow or deep trenches, filter beds, drip, spray, or minimum or zero discharge systems for adequately treated effluent can be achieved on almost any site where adequate square footage of space is available. Performance of such dispersal systems does not depend on type, depth, or color of soil present at the site. In the 21st century, emphasis needs to be put on the use of appropriate onsite treatment and dispersal systems and on the permanent operation and maintenance of those systems rather than on the acceptance or rejection of a lot for an onsite system based on soil evaluation and soil criteria. With the availability of pre-engineered and prepackaged treatment and effluent management systems in the market today, engineers now have more than 500 different ways of developing onsite solutions for wastewater sys- tems. Soil and site characteristics as well as environmental sensitivity typi- cally determine which onsite system may be used for a given project. How- ever, a designer may decide to standardize onsite wastewater solutions using a small number of system categories that address most of the soil and site conditions in a given region. Photos 5.1 through 5.10 show various projects that use advanced effluent © 2006 by Taylor & Francis Group, LLC 140 Advanced onsite wastewater systems technologies Photo 5.1a Installation of a small (10-ft long and 1-ft wide) trench on a slope. Note that the backhoe is digging in the trench just by scratching the ground surface. Photo 5.1b Close view of the small and shallow trench. Notice the fiberglass cover placed on typical four inch perforated drain pipe placed in the trench. There is no gravel used in this trench. © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 141 Photo 5.1c Side view of the small and shallow trench before covering the trench with soil material removed from the area. Photo 5.1d Side view of the same trench after covering the trench with the top soil that was removed from the area. © 2006 by Taylor & Francis Group, LLC 142 Advanced onsite wastewater systems technologies Soil and site evaluation: then and now Soil and site evaluation has been an integral part of the onsite wastewater business and its regulation. With the availability of various treatment sys- tems, the use of soil for treatment of primary effluent or raw wastewater (septic tank effluent) is not necessary. When the use of advanced onsite wastewater systems is proposed, subsurface effluent dispersal systems can be adequately sized, designed, installed, and operated for any soil and site conditions; thus, there is no need to have regulatory requirements for soil and site conditions to determine whether a proposed site is “suitable” for an onsite system. The soil and site evaluation that is typically done for septic systems generates such information as a soil description and the depth to limiting conditions. This information is not needed for sizing of a dispersal system for secondary or better quality effluent. A simplified approach for developing regulatory requirements for using advanced onsite systems is proposed later in this chapter along with a proposal for set-back requirements and sizing criteria. Some of the other factors associated with site evaluation would remain important, including determining slopes; location and distance to environmentally sensitive areas; location of water supplies; location of sur- face water bodies; location of utilities and easements; availability, location, Photo 5.1e Looking at the house from the bottom of the slope. The small and shallow trench is located between the house and the shrub. © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 143 and type of power (115 VAC, 230 VAC, single-phase or 3-phase); access to site for construction purposes; and location of existing underground utilities. Currently, for designing onsite systems, most of the site evaluation fac- tors required for choosing the appropriate advanced onsite wastewater tech- nology are simply ignored and a “site evaluation” is essentially a description of the sidewalls of some pits dug on the property, which is typically done for soil mapping purpose. A true site evaluation includes many more factors for locating and choosing the appropriate wastewater treatment system and focuses less on two pits excavated or four auger holes bored on the property. A site evaluation for use of onsite systems should not be an exercise in soil mapping. The owners of onsite wastewater systems are not interested in knowing the color, texture, and structure of individual soil stratum, but they are interested in making sure that their onsite systems work on their prop- erties and meet their needs for adequate wastewater management. A site evaluation process that truly results in meaningful information that a designer needs and can use for selection, design, and layout of an onsite system can be justified and will be accepted by the onsite professional; but a site evaluation process that simply meets the regulatory requirements for obtaining a permit cannot be justified and will not be accepted by onsite wastewater professionals. Photo 5.2 Small and shallow placed gravel-less trench that is used for dispersing up to 1,000 gallons per day effluent from an advanced onsite treatment system. Note that the trench is between Dr. Craig Jowett and Dr. Kevin Sherman. © 2006 by Taylor & Francis Group, LLC 144 Advanced onsite wastewater systems technologies A variety of dispersal systems for individual home or small (less than 1000 gal per day [gpd]) commercial systems can be pre-engineered with little knowledge of soil characteristics and can be installed on a site in a manner that allows for adequate assimilation of effluent. Based on the site charac- teristics of the proposed location, an appropriate type of pre-engineered dispersal system can be selected and installed. It is possible to educate and train installers of onsite systems to install such pre-engineered dispersal systems with the availability of onsite engineering and other design expertise when needed. Effluent dispersal systems should be selected and sized based on a site’s assimilative capacity for the design flow and the nutrient loading, rather than just based on soil characteristics. Soil and site conditions that are Photo 5.3a A 5-ft wide and about 100-ft long trench that was dug down to about 10-ft depth to the sand layer and filled up with gravel. The “L” shaped trench is used to disperse about 5,000 gallons per day effluent from an advanced onsite treatment system that serves a service station. Photo courtesy of Mr. Daniel Pavon of Aquarobic International, Winchester, VA. © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 145 Photo 5.3b Chambers were used to cover the four inch perforated pipes placed in the trench. Photo courtesy of Mr. Daniel Pavon of Aquarobic International, Winchester, VA. Photo 5.3c Final view of the area where the trench is now dispersing the effluent from a SBR treatment system. Note that one end of the “L” shaped trench is at the white observation pipe and the other end is next to the dumpster. © 2006 by Taylor & Francis Group, LLC 146 Advanced onsite wastewater systems technologies Photo 5.4a Drip dispersal system for an individual home. Note that the drip tubing is installed in five feet wide trenches. Trenches are open and the system is being tested before covering the trenches. Figure 5.4b Drip dispersal system area a few months after installation. Note that the grass is established and under the grass cover, effluent from an advanced onsite system is dispersed using drip lines. [...]... systems, regulatory reviews of individual home onsite systems and © 2006 by Taylor & Francis Group, LLC 166 Advanced onsite wastewater systems technologies even large-scale onsite systems should be conducted only when such reviews result in value-added responses Currently, enforcement of onsite systems is generally on the permitting end By not allowing onsite systems simply because regulators are unfamiliar... TMYL (5. 6) where: W = flow in gallons per day per home TMYL = total maximum load in inches/year 0.01344 = conversion factor Equations 5- 5 and 5- 6 can be used for permitting individual and cluster home onsite systems that use advanced onsite treatment systems with minimum information on soil and site conditions With this approach, licensed designers, engineers, and others will be able to design systems. .. design in field conditions The current approach for regulating individual home and small onsite systems should be revised significantly In Chapter 7 an approach is proposed for developing a solution-driven and performance-based regulatory framework for managed onsite systems that would allow use of advanced onsite technologies whenever and wherever they are needed or desired Because soil is porous, water... hydraulic force (ΔP) equal to about 35 ft of head Similarly, we can solve the equation for a trench-type dispersal system that is 3 ft wide and 1 ft deep and the value © 2006 by Taylor & Francis Group, LLC 158 Advanced onsite wastewater systems technologies for ΔP will be about 45 ft of head Does this mean that if pressure is maintained equal to or greater than 45 ft of head in the pipe, effluent can... autooxidation Nitrification Nitrite (NO 2-) O2 Nitrogen Treatment by Onsite Wastewater Treatment Systems Nitrification Assimilation & Dentrification Nitrate (NO 3-) Denitrification Nitrogen gas (N2) Organic carbon Nitrogen Treatment by Onsite Effluent Dispersal Systems Vegetation and Nitrogen gas (N2) Figure 5. 1 Transformation of various forms of nitrogen in an onsite wastewater treatment and effluent dispersal... of a © 2006 by Taylor & Francis Group, LLC 164 Advanced onsite wastewater systems technologies Table 5. 1 Values of “d” for various types of effluent dispersal system and design parameters © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 1 65 responsible management entity that can own and operate onsite systems on a permanent basis A simple relationship exists.. .Chapter five: Effluent dispersal and recycling systems 147 Photo 5. 5a Drip system for effluent dispersal installed in open area using a vibratory plow Source: Photo courtesy of Mr Robert Mayer of American Manufacturing, Inc., Manassas, VA Photo 5. 5b Drip system for effluent dispersal installed in wooded area using a vibratory plow © 2006 by Taylor & Francis Group, LLC 148 Advanced onsite wastewater systems. .. develop land using advanced onsite systems can confidently do so without having to worry about whether the land will “perc.” A solution-driven and performance-based regulatory program will allow a responsible management entity to offer wastewater solutions using advanced onsite systems in areas where sewer extensions are not practical or not desired and in areas where conventional septic systems are failing... impact on the ground © 2006 by Taylor & Francis Group, LLC Chapter five: Effluent dispersal and recycling systems 151 Photo 5. 9a Evapo-transpiration beds for dispersal of effluent from an advanced onsite wastewater treatment technology that serves three individual family homes Note the picture is taken few months after the installation Photo 5. 9b Evapo-transpiration beds about four years after the installation... agencies and wastewater professionals working in the private sector, developing monitoring requirements and performance standards for any onsite system will be relatively easy People will then have adequate access to all the available technologies for managing wastewater onsite Such a performance-based monitoring and regulatory system can also help “weed-out” inappropriate wastewater systems that may . management level (see Chapter 6 onsite systems should be revised significantly. In Chapter 7 an approach is © 2006 by Taylor & Francis Group, LLC 156 Advanced onsite wastewater systems technologies generated. 5. 5b Drip system for effluent dispersal installed in wooded area using a vi- bratory plow. © 2006 by Taylor & Francis Group, LLC 148 Advanced onsite wastewater systems technologies Photo 5. 6a. region. Photos 5. 1 through 5. 10 show various projects that use advanced effluent © 2006 by Taylor & Francis Group, LLC 140 Advanced onsite wastewater systems technologies Photo 5. 1a Installation