Field Trip to the Wastewater Treatment Plant

Treatment Process | Organisms in Sludge

Albuquerque's Southside Wastewater Reclamation Facility (SWRF), Commonly called the sewer plant, treats all of the City of Albuquerque's wastewater emanating from its homes and industries. It does not process the street runoff which flows through the arroyos directly into the Rio Grande. (runoff contains pesticides and fertilizers, oil and lead, and is a significant pollution source for the river.) The plant is located on 2nd Street SW just south of Rio Bravo Blvd. If you have already been to the south valley bosque then you passed it on the way there.

Route to the Plant: From TVI take interstate I-25 south to Rio Bravo Blvd. and go west (right) to 2^nd Street. Turn left (south) on Second Street and go about a quarter mile to the first paved drive on the right into the plant. Wait until everyone arrives so we enter as a group. We will drive to the Training Bld. (T) on the south side of the plant. You should wear canvas shoes or boots on our tour because we may walk through a small amount of water (fresh)or mud. After a short discussion in the training building we will walk around the plant. Bring water and sunscreen, if needed, and appropriate outdoor clothing.

NO SHORTS OR OPEN-TOED SHOES are permitted. Our tour will last about 2 hours.

The SWRF receives upwards of 75 million gallons of wastewater daily and treats it with primary, secondary, and advanced processes.

Primary Treatment - the first stage of treatment removes debris and floating materials and allows the largest particles to settle out. A grit filter and bar screen as well as a primary clarifier (settling tank) are the components of this process. The debris from the bar screen and grit chamber are sent to the dump. The solids from the settling tanks become part of the sludge processing.

Secondary Treatment - the next stage of treatment uses bacteria and other microorganisms (see later page) naturally present in wastewater to consume the organic matter still present in the liquid and thus reduce the Biological Oxygen Demand (BOD, a.k.a Biochemical Oxygen Demand). Oxygen is provided by aeration (infusing air into the water) to sustain the microorganisms. If the wastewater were simply discharged into a river or lake the oxygen would be consumed from it and cause oxygen depletion which threatens aquatic life. Secondary treatment generally removes 90% + of the organic materials, but not the inorganic materials such as nitrates, phosphates, etc. These must be removed by advanced or tertiary treatment. Albuquerque's new improvements retain the wastewater in an oxygen poor state so that microorganisms are forced to remove oxygen atoms from nitrates and nitrites, with nitrogen coming off as a gas, thus reducing the nitrogen compounds remaining in the effluent.

Advanced Treatment - any step beyond secondary treatment to further reduce the organic or inorganic materials present. May include sand, gravel or charcoal filters, or chemical processes. The SWRF is an advanced treatment facility as explained above.

Tertiary Treatment - Uses advanced processes and either reverse osmosis or distillation to remove all contaminants, yielding pure, drinkable water.

Biological Oxygen Demand (BOD) a.k.a. Biochemical Oxygen Demand, is the oxygen required to breakdown the contaminants present in wastewater, mostly organic materials.

Chlorine - generally a compressed gas in liquid form, it is injected into the

effluent (called chlorination) prior to discharge to kill any living microorganisms. A contact basin, shaped like a maze, is used to increase the contact time with the chlorine.

Pretreatment - The process, required by law, by which certain businesses and industries remove pollutants before discharging them into our wastewater system.

Coliform - bacteria which inhabit the large intestines (colons) of many animals. Easy to identify in tests, their presence is used to detect fecal contamination, which may mean the presence of pathogens (disease causing organisms).

Sludge - the solids separated from the liquid during processes. Sludge is produced by the primary and secondary clarifiers and is composed ultimately mostly of bacteria and some organic solids. It is sent to the Soil Amendment Facility and the Pilot Composting Facility, which you may visit, to be turned into compost or soil. Sludge is free of living microorganisms due to the high temperature and the combination of aerobic and anaerobic treatment it receives.

Anaerobic digestion - A process of breakdown by microorganisms which live in the absence of oxygen. These organisms produce a gas similar to methane which can be used as a fuel. The plant uses some of this digester gas to power gas fueled electric generators by which they make about 95% of the electricity used by the plant.

Figure 2: Wastewater Treatment Process

Figure 3