A

Aerobic Baffled Reactor (AeBR): A baffled reactor that aerates the water flowing through it.

Anaerobic conditions: Find out about anaerobic conditions here.

Anaerobic digestion: The resulting effluent from septic tanks and DEWATS is not of suitable quality for applying to the soil surface, but must instead be diverted to underground soakage fields or pits that contaminate water tables and inevitably fail in time.

Auto desludging system: A pump that pumps sediment from a sump at periodic intervals into a vermifilter that filters the sediment out before the water returns to the sump.

B

Baffled reactor: Comprises a series of settling tanks or reactors (also called sedimentation tanks, settling compartments, sedimentation chambers, clarifiers or settlers) that settle solids out of wastewater.  The liquid is forced to flow up and down from one compartment to the next, settling out solids in the process. To retain scum, the outlets of each tank are placed slightly below the liquid surface. Each settling chamber should be vented. 

Bell siphon: a simple device using gravity to dose the irrigation drippers. Also called "ebb and flow", there is a fill phase where the water builds up in the irrigation tank and a drain phase where the water is released. This generates pressure on the irrigation lines and evenly distributes it to the drippers. How to make a bell siphon »

Siphon systems require routine monitoring and occasional maintenance. “Dribbling” can occur when the siphon bell becomes saturated, suspending dosing and allowing the wastewater effluent to trickle out under the bell. Dribbling can occur because of leaks in the bell or a siphon out of adjustment. Today, pumps are favoured over siphons because of the greater flexibility in site selection and dosing regime.

Biofilm: Also known as "biological slime", biofilm is formed by bacterial colonies that adhere to each other and to a surface. Biofilm proliferates in oxygen rich, wet environments with an organic food source, such as sewage. Wikipedia

Biological oxygen demand (BOD): See Biological oxygen demand.

Blackwater: Wastewater containing human waste such as faeces.

BOD: Biological oxygen demand.

C

Centrifugal pump: These have rotors or "impellers" that spin. The rotational energy draws the fluid into the pump and forces it out of the outlet point at an increased velocity. Centrifugal pumps are not positive displacement pumps. They are not good for pumping liquids that contain lots of solids or hair.

D

DEWATS: Decentralised wastewater treatment system. DEWATS are usually anaerobic and utilise multiple septic tanks in series. DEWATS do not treat sewage to the level required for surface irrigation.

Displacement: A phenomenon that occurs when one fluid pushes another fluid out of a container or a confined space by the introduction of another fluid. Learn about displacement here.

E

Equilibrium water level: The water level the system normally operates at without surges of influent raising that level by displacement. If water enters the system faster than it exits, the water level will rise above the equilibrium level. Learn about equilibrium water level here.

F

Fall: the vertical drop from point A to point B over a certain distance.

Flexible impeller pump: A positive displacement pump with an impeller made from rubber. Suitable for thin and viscous fluids as well as solids in suspension. They are a highly versatile pump system with self-priming capability. Macerator pumps are flexible impeller pumps.

G

Greywater: Wastewater not containing human waste such as faeces. Greywater includes bath, shower and kitchen wastewater.

Gravitational force: Gravity acts on all objects in the downward direction. As incline increases, velocity increases. Hydraulic gradient increases with angle of inclination

H

Helical rotor pump: Helical rotor pumps, also known as progressive cavity pumps or cavity pumps, are a type of rotary positive displacement pump that has a single-threaded helically shaped rotor turning inside of a double-threaded helically shaped rubber stator. These pumps can handle difficult, thick, and solid-laden liquids. The helical rotor pump provides high head even at low rpm.

Humus:  The dark organic matter that is formed by the decomposition of plant and animal matter.

Hydraulic Gradient: The slope of the water table, i.e. the change in water level per unit of distance along the direction of maximum head decrease.

Hydraulic loading: the volume of wastewater applied to the surface of the process unit per time period. Hydraulic loading rate = the volume of waste water per day / Area. 

Hydraulic retention time (HRT): The time interval over which the influent is kept inside the reactor before it exits as effluent.

M

Modular units: Vermifilter units constructed using the same methods and materials and that are the same dimensions. They can be installed in parallel or in series.

N

Nutrient cycle: Find out about the nutrient cycle here.

O

Oxygen demand: Find out about oxygen demand here

P

Positive displacement pumps: Positive displacement pumps draw fluid into a cavity, then force the fluid out of the cavity through suction.

R

Reactor: The tank or vault that contains the media substrate and that does the treatment.

S

Simplified sewers: Also known as small-bore sewers, this is a sewer system that collects all household wastewater (blackwater and greywater) in small-diameter pipes laid at fairly flat gradients. Wikipedia

Surge capacity: A tank's surge capacity is defined as the volume of the portion of the tank that is above its equilibrium water level. Learn about surge capacity here.