Water Supply Exam Review 2021

Vocabulary and key concepts from the Water Supply module assessment, covering water chemistry, microbiology, resource development, treatment, and management models.

Conductivity

A measure of water’s capability to pass electrical flow which is directly related to the concentration of ions or electrolytes; it is measured in $\text{micro- or millisiemens per centimeter}$ ($\text{uS/cm}$ or $\text{mS/cm}$).

Specific conductance

A conductivity measurement made at or corrected to $25^\text{o} C$; it is measured in $\text{micro- or millisiemens per centimeter}$ ($\text{uS/cm}$ or $\text{mS/cm}$).

Salinity

The total concentration of all dissolved salts in water; for drinking water it is usually reported in $mg/L$, though it can also be reported in parts per thousand or $g/kg$.

Total dissolved solids (TDS)

The sum of all ion particles smaller than $2 \text{ microns}$ ($0.0002 \text{ cm}$), including salinity-related electrolytes and other compounds such as dissolved organic matter.

Faecal indicator organism

A 'good' indicator should be universally present in human and animal faeces in large numbers, not multiply in natural waters, persist similar to faecal pathogens, respond similarly to treatment, and be readily detected via inexpensive culture methods.

Culture techniques

Microbial quality measurement methods (using broth, agar plates, or cell cultures) that detect living organisms based on infection or growth, indicating viability or infection rather than just physical presence.

Hydraulic conductivity

A measure of an aquifer's ability to transmit water, measured in $m/s$; it varies by geology, being significantly higher in sand due to pores between grains compared to the crystalline structure of limestone.

Darcy’s Law

A principle used to estimate flow rate in an aquifer, defined as $Q/A = -K \times (\frac{dh}{dl})$, where $K$ is conductivity and $\frac{dh}{dl}$ is the hydraulic gradient.

Biofouling

A biological reason for the decline in borehole yield over time, often involving the accumulation of contaminants or organic growth that impacts flow.

Wet harrowing

A critical maintenance activity involving the cleaning of filter layers to maintain flow and treatment performance in a community slow sand filter.

Schmutzdecke

A biological overgrowth layer in a filter; its removal or disposal is a maintenance activity required to sustain performance in slow sand filtration.

Residual chlorine

The level of free chlorine maintained to provide ongoing disinfection; recommended at $\text{greater than or equal to } 0.5 mg/L$ after $30 \text{ minutes}$ contact time at the tap at $pH < 8.0$, or $0.2 mg/L$ in stored household water.

Demand-responsive approach (DRA)

A rural water supply model focused on assessing and responding to community demand, primarily through financial contributions and participatory decision-making to promote a 'sense of ownership'.

Service delivery approach

An approach that builds on DRA but places greater responsibility on governments to provide ongoing financial, administrative, and technical support for rural water supply management.

Hazardous event

Within Water Safety Planning, an event like flooding of a service reservoir that results in the exposure of workers or the public to contaminated water if treatment capabilities are overwhelmed.

Control measures

Actions taken to reduce hazards, such as flood protection, improved fencing, or the cessation of source water abstraction during high turbidity events.

Critical limit targets and triggers

Monitoring parameters like rain events, flow rates, or turbidity levels (e.g., $pH < 8.0$ or specific $mg/L$ limits) that, if exceeded, initiate remedial actions like boiling water advice.