“ The most common and widespread health risk associated with drinking water is microbial contamination and therefore the control of microbial contamination must always be of primary importance .” removed at the source or by the wastewater treatment processes .
The design of maturation ponds is critical ; if the pond is too shallow ( or has large open surface areas ), the wind will stir the water and rise the sediments at the bottom of the pond , increasing the turbidity .
Water reuse plant
Proper operation and maintenance is very important to ensure the required water quality over time . Treatment process units must be thoroughly monitored . The monitoring data should be stored and reviewed to ensure that each of the treatment units performs as intended . Impromptu maintenance should also be carried out based on the monitoring results — however , risk-based maintenance is still the most important tool to properly maintain the plant .
Filters should have a filter-to-waste option to ensure low turbidity ( that is , it should prevent particle breakthrough ) after backwashing to ensure proper removal of Giardia and cryptosporidium .
If a unit process is out of a target specification it should automatically go into bypass or recycle mode , provided the final water quality can still be attained . If not , the plant should be shut down and the problems fixed .
Monitoring instruments
On-line monitoring , using high-quality instrumentation , is not optional for direct and indirect potable reuse plants because of the high demands placed on treatment efficiency and water qualities .
The feed and final water of each of the treatment units should further be measured at a high frequency to detect treatment failures .
Plant operators / process controllers
The process controllers of WRPs should have a sufficient skills level to understand each of the treatment processes on the plant . Sufficient guidelines or operational manuals should be available on site at each of the applicable treatment process units that can guide a process controller , especially during emergencies . All process controllers must be able to use and calibrate handheld sampling and measuring devices .
Public participation
Good analytical results and data management ( archiving ) is a very important aspect for public participation and motivating the use of certain technologies . The laboratory should also set high standards and be promoted to set the minds of the public at ease .
Open communication channels with the public will further enhance public participation in , and acceptance of , water reuse schemes .
Conclusions
It is emphasised in the report that the success of a DPR scheme depends on five important elements , namely :
1 . A reputable specialist team to accompany the project from design to implementation ;
2 . A robust treatment training ;
3 . A proven treatment technology with a good track record elsewhere ( pilot plant studies will further prove a technology );
4 . Water quality monitoring ; and
5 . Good communication at all levels and between all stakeholders , and continued training and research .
The guidelines provided here have focused on water quality monitoring as an important link in the various potable reuse chains . Important conclusions drawn from the development and public presentation of the guidelines are summarised below .
With good technologies , personnel and communication protocols , barriers and monitoring systems in place , direct and indirect potable reuse is becoming increasingly attractive as a water source .
Although the technological development , and analytical and engineering procedures for monitoring are well advanced and potable water quality can be ensured , there are still a few challenges and issues that are receiving attention and which are currently studied further at research centres across the world .
The successful implementation of IPR and DPR schemes depends strongly on the expertise of design and monitoring teams and the availability thereof in the region . A good example is the management of brine streams , and addressing the technological and economic challenges that are evident in this regard .
In the design of DPR monitoring programmes , information about the water quality should be clearly communicated to the consumer as well as within the water service provider . Negative communication should be avoided at all cost ( without distorting facts ), because any negative information and publicity about a water quality event at the consumer point will be blamed on DPR .
A good monitoring programme will allow the water quality manager to convince all
10 Water Sewage & Effluent July / August 2017