Septage disposal requirements have come a long way since the days when haulers could simply discharge their loads into an open pit at a sewage treatment plant or off-load them into a field or lagoon. This process was often neither regulated nor monitored. Haulers submitted their own estimates of what and how much they dumped for billing purposes. This practice created a very real threat of ground water, lake and stream contamination.
The EPA issued strict new guidelines (under 40 CFR part 503) concerning septage land disposal. Haulers were given the choice of meeting the agency’s land disposal standards or utilizing the overextended services of existing sewage treatment plants.
Septage receiving can be tough on a treatment plant’s operation. Septage is 6 to 80 times more concentrated than municipal wastewater. It typically also contains significant levels of grease, scum, grit, rocks, rags, hair, plastics and other debris. If not treated properly, these solids can disrupt the treatment process. Many plants started receiving septage by simply allowing haulers to dump in a manhole upstream of the plant headworks, often with just a coarse manual bar rake for protection from heavy debris. This solution proved maintenance intensive. Plant biological processes can be disrupted by sudden surging of highly concentrated organics. The solids loading on the plant could cause significant ragging and subsequent downtime of pumps and other downstream equipment. The current challenge for many municipalities is to create enough septage disposal capacity to meet more stringent EPA regulations while not overtaxing their treatment processes.
To meet this new burden on treatment plant facilities, plants are opting for a more complete solution by the installation of specialized septage receiving systems. These systems are designed to streamline septage receiving, control hauler access and pre-treat by grinding and screening septage solids to reduce plant loading. This screening system forms an essential part of plant pretreatment facilities. Along with this often comes new security measures to identify and assure only permitted septage is received. One such system is the SPIRALIFT SR manufactured by Franklin Miller Inc., a leading manufacturer of sewage processing equipment,
Plants often limit the percentage of grease in a given septage load to 3:1 or 3 parts solids to 1 part grease and require a separate offload and processing of loads with a high percentage of grease.
To help defray the cost of this additional burden, plants are assessing haulers fees to process their septage loads and pay for the capital investment in equipment and facilities. These rate structures vary widely from plant to plant and state to state. Some plants charge a flat fee per load and a permit fee while others charge on the basis of actual volume received using flow metering equipment to measure the gallons of each load. Some rates are determined not only by the flow but also the content or source of the septage. Many plants limit their intake to domestic septage or porta potty waste. Rates range from $10.00 – $250.00 per 1000 gallons received. To further offset costs of operation and capital improvements many plants will receive septage originating outside their district.
Septage Receiving equipment, generally consists as a minimum of a screening device, valve and a controller. More sophisticated systems include a solids conditioning grinder, a tramp trap to collect heavy objects, a flow measurement device and sometimes ph meters or sampling devices. Some plants that can handle the solids loading in their existing plant systems are opting for a grinder and special control system to monitor hauler loads.
The preferred screen design for septage consists of an auger screw with brushes located within a large tank that rotates against a perforated screen. As the brushes sweep the screen a spray wash system washes organics off the solids while the solids are conveyed up the unit discharge. At the top most portion of the unit is a compaction area for reducing moisture content of the solids. The solids are deposited into a container for disposal in a washed and compacted condition with a reduced moisture level for lower weight.
If it is desired to remove sand and grit or grease from the septage, the screening system can include additional stages of screening. For grit removal, a second stage of the system includes a sedimentation tank where grit is collected and discharged through an additional inclined screw. For grease removal, a the system can be fitted with a grease skimming device that collects grease and deposits it in a separate discharge chute.
System configurations can be modified to fit in a particular plant location. For example the system can be provided with a straight thru configuration or a right-angle design with inlet and grinder off to the side.
Offloading and processing is usually completed in about 10 minutes. Systems can be configured with an inlet piping arrangement for multiple trucks to hook up or process simultaneously.
Besides the basic control system, a data collection control system can be installed. This system may be a part of the main control or built into an auxiliary panel.
According to the EPA, “Records of septage sources and volumes and routine sampling of septage loads are an essential part of a comprehensive septage management program.” This is accomplished with the addition of a data collection system. With this system, the haulers are provided a magnetic card that contains their hauler id. When the controller authenticates the card, after it is swiped, the system operation is only then initiated. As the load is discharged, the system tracks gallons dumped, the date and time along with data from other optional instrumentation. The control then prints a receipt which includes a record of the transaction. Simultaneously, the transaction data is stored in the system memory for use by the plant for billing and tracking purposes.
If the equipment is to be placed in an exterior location, attention must be paid to protecting the system from freezing. In this case a weather-proofing is provided to keep all lines and tanks above the freezing temperature. The controllers are often placed in a protected or shaded area to avoid direct exposure to sunlight especially in sunbelt locales where temperatures ranges can be severe.
Septage: The liquid, solid, and semisolid material that is pumped from a septic tank, cesspool, porta-potty or other primary treatment source (i.e., in accordance with 40 CFR Part 503).
Septic tank: A buried, preferably watertight tank designed and constructed to receive and partially treat raw wastewater. The tank separates and retains settleable and floatable solids suspended in the raw wastewater. Settleable solids settle to the bottom to form a sludge layer. Grease and other light materials float to the top to form a scum layer. The removed solids are stored in the tank, where they undergo liquefaction in which organic solids are partially broken down into dissolved fatty acids and gases. Gases generated during liquefaction of the solids are normally vented through the building’s plumbing stack vent.
Auger – a cork-screw like conveying device generally provided in a shaft-less configuration that can be combined with a screening system.
Grinder – A machine (comminutor) for reducing the particle size of solids either in a pipe or in an open vertical or horizontal system.
Wash System– a wash system generally consisting of an array of nozzles that sprays a concentrated jet of water to dislodge and remove soft organics from other solids.
Headworks – the front or first portion and main collection area of a wastewater treatment plant where solids screening or grinding equipment is located.
Hauler – Trucker with vacuum truck that removes the septage from the tank and transports it to the waste water facilitiy.
The S270-SRH Hauler Station monitors the operation of SPIRALIFT SR or TASKMASTER TT and provides an interface for septage haulers to operate the system. It also records transactions and provides billing information to the plant. records. Read more by clicking here.
The SPIRALIFT SR system facilitates the organized receiving of septage into a treatment plant and provides primary treatment. This system can be provided with a complete control system for monitoring hauler loads and recording billing information. Read more by clicking here.
The TASKMASTER Model TT is a grinder with a self-contained tramp trap that allows heavy solids and metals to settle out prior to reaching the grinder. It also features a quick access slide gate for removal of the tramp materials. Read more by clicking here.
William Galanty is President of Franklin Miller Inc. 60 Okner Pkwy. Livingston, NJ 07039 1-800-932-0599
Which manufactures septage receiving systems as well as grinders, comminutors, shredders and other screening equipment.