Effluent from in-home dialysis treatments can have a negative impact on septic systems
Dialysis is a treatment for kidney failure that removes waste and extra fluid from the blood using a filter. There are two main types:
- Hemodialysis (HD): Where blood is taken out of the body through a complex set of tubes, run through a filter called a dialyzer, cleaned of various impurities, and returned to the patient.
- Peritoneal Dialysis (PD): In this less common form of dialysis, a synthetic tube is placed in the abdominal cavity, which then allows dialysis by exchange of dialysis fluid at regular intervals.
The effluent from both types of dialysis has been shown to damage onsite systems and should not be discarded into septic systems. It will add additional water and contaminants the septic system is not designed to treat or remove, and can negatively impact the beneficial microbes needed to treat the wastewater. The effluent is not sanitized, so it could contain harmful pathogens. The pH of most effluent should be neutral. Both systems produce effluent containing protein (albumin) and sodium chloride, along with potassium, sodium, bicarbonate, phosphorus and nitrogen waste products (similar to urine).
HD impacts on septic systems
During its passage through the filter, the blood comes in contact with dialysate (primarily water and sodium), which mirrors the body fluid except for the presence of impurities.
In the case of home HD, there are two waste streams:
- Reverse osmosis reject water, which is not harmful to onsite systems. But since it is clean water it is better for it to be reused than added into the system, as the system was not necessarily designed for the additional water. It greatly depends on what type of RO system they have, as the ratio of source water to product water in an RO system can be as high as 10-to-1, (i.e., for every gallon of product water produced by the RO system, 10 gallons of source water is needed, with 9 gallons of water going down the drain as wastewater) which could place significant demands on the septic system.
- Post-dialysis effluent has a high concentration of sodium and chloride (over 3,000 mg/L for both) which can alter or kill organisms, or cause unwanted and incorrect organism overgrowth in the septic tank and downstream. It can also negatively impact concrete. It also contains small amounts of glucose (1 mg/L reported by one company).
Though the typical duration for a patient varies, HD is done every day with each individual session typically ranging from three to six hours and using around 100 gallons per week.
PD impacts on septic systems
PD influent for the patient has a glucose concentration ranging from 1.5 to 4.25 percent glucose (1.5 gm/100 mL of glucose = 15 gm/L (or 15,000 mg/L; 4.25 percent PD fluid contains 42,500 mg/L). Depending on the system, 40 to 50 percent of the glucose is absorbed by the patient, so this generates BOD in the effluent. PD is done every day for six to eight hours with six cycles every day generating approximately 25 gallons of effluent per week. The high glucose content of PD effluent can also promote the formation of a copolymer that can coat the surface of the soil and block the lateral lines.
What can you do and where should it go?
The first question to ask is what kind of system they are using, and request a report on the amount of RO water and effluent characteristics. Currently, many patients are told to drain their bags into the toilet. The medical field also recommends following the effluent with a cupful of bleach that should be flushed after five minutes since the effluent can contain harmful viruses and bacteria. This also creates a negative impact on the septic system microbes and should not be done. Instead, the septic professional or patient needs to check local regulations and preferably the effluent from dialysis should be discharged belowground into a shallow rock pit.
About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association (MOWA) and the National Onsite Wastewater Recycling Association (NOWRA), and serves on the NSF International Committee on Wastewater Treatment Systems. Send her questions about septic system maintenance and operation by email to firstname.lastname@example.org.