Update from Brendon Harkness, Engineer in Sustainable Development

This provides an update of progress, and recommended decisions / actions relating to provision of household water for the Kwa mwanamangare-kwa Muina community. A drilling permit was granted by the Paganai basin water officer on 14 March 2019 and allowed drilling to be completed by 13 June 2019.

Recent Events

Borehole Drilling

A borehole was drilled and developed by a private drilling contractor - Borehole Masters (BHM) - during April 2019, and testing was undertaken for quantity and quality. BHM staff were extremely cooperative and staff engaged well with the community and BHW partner staff, however challenges were encountered in achieving the required technical standards, although it is likely that many apparent issues could be related to poor communication by BHM. Technical supervision was sought during drilling and testing, and of the two options identified; one was not received well by the community, and the other elected not to continue in the role after drilling had commenced - possibly as a result of a communication breakdown.

BHM elected to drill in a different location to that identified by the report by Radiator Hydrogeology, and drilling was completed with good community / stakeholder engagement managed by Robert. However, despite repeated requests for confirmation of drilling observations and critical decision points as outlined in the contract specifications, BHM chose to drill to the full depth of 180m, developed, and completed the bore and returned to Dar, which prevented any input and resulted in a number of areas of non-compliance with specifications. 

Due to these difficulties and poor confirmation of outcomes, a decision was made to hold back final contract payments until the borehole completion report was received and was seen to adequately cover the drilling process and outcomes.  

Pump Testing

The pump test results completed by BHM were considered inconclusive and a second opinion was given by a NZ based hydrogeologist, Wayne Russell from GWS Ltd. His summary suggested that the bore cannot sustain 4 to 5 m3/hr we were hopeful in obtaining, but more importantly, that further pump testing was required to demonstrate confidence in a sustainable yield. 

Following a successful negotiation with BHM, three days of further testing was completed (paid for by BHW), and despite inconsistencies and what appears to be regular pump shutdowns due to the lowering of water levels and incorrect pump positioning, we believe there is sufficient evidence to support the installation of a pump installed at a lower position, and rated for sustainable yield of 1 m3/hr. 

A circa 4kWp solar powered pump system should be capable of producing up to 10m3/day based on this rate, and while the daily volume is lower than the 20m3 expected to serve a population of 1,000 people, Sphere standards define total basic water needs as 7.5 - 15 L/s so it is anticipated that water can be managed to ensure appropriate use, and coverage prioritised for the immediate community. 

Water Quality Outcomes

Throughout development and testing of the borehole, photos have indicated discoloured water (sampled water from pump testing on right in contrast with local bottled water on left), which is typically as a result of sediments (silt, sand etc) and/or chemical parameters (iron, manganese) however without information on the borehole development process undertaken by BHM, it is unclear how much of this can be attributed to the temporary disturbance of silts during drilling, the location of the test pump in relation to the slotted/screened sections of the bore casing, or permanent characteristics.

Water quality tests were undertaken by a laboratory in Dar es Salaam, and show no bacteriological issues (i.e. E.coli), but found levels of salts (salinity), total dissolved solids, iron, manganese and hardness above WHO and local maximum allowable values.

While many of these elements are considered more aesthetic than toxic, research indicates links between salinity in drinking water and maternal health issues for instance, so it is recommended that water be used for non-consumptive purposes until the most appropriate treatment solution is determined. 

The laboratory suggested that element concentrations would reduce after 2-3 months of pumping, however it must be noted that the reliability of local testing laboratories (Tanzania) is not known.

Water Treatment Options

Unlike the treatment of pathogenic contamination which can be managed using filtration and chlorination, the levels of chemical elements present are likely to require a combination of softening, aeration, filtration and potentially reverse osmosis; and these can be expensive to install, complex and energy intensive to operate. A number of small-scale plant options are viable - including a proven GE E-series ultra filtration unit (see photo), and a unit manufactured in India and installed in a BHW partnership in Pakistan - and similar units could be considered in the medium term.

An alternative option is to use solar distillation, a simple non-powered solution that relies entirely on solar radiation to provide condensate within a sealed, household level, unit.

A multitude of DIY instructions are available online using standard hardware, and a number of commercial units have also been identified as outlined below.

F-cubed Carocell distillation unit - Melbourne (NZ$1,200) (left) : Watercone solar powered water desalinator (middle) : Rainmaker 550 Solar Water Distiller - USA (NZ$800) (right)

This technology is simple and robust, and appropriate for a small number of households, but would also require significant capital at the scale being considered for this community, and research suggests varying levels of output based on the weather and the condition of the unit.

It may be possible for local entrepreneurs to build, assemble and maintain effective units - which can double as a rainwater harvesting surface - but this would require a degree of technical support, particularly during the early stage of development.

Recommendations and Next Steps

It is recommended that the following steps are considered / achieved during a visit to the community by myself and Kevin Honore, BHW Partnership Facilitator, planned for 1-3 September 2019:
• Meet with local solar suppliers to agree on scope, location and details for installation of a circa 4kWp solar pumping system, at an estimated cost of US$17,000 to $19,000
• Discuss options for supplementary water supply and treatment including rainwater harvesting, community scale treatment, or local distillation unit manufacture
• Establish confidence in the potential for a community-appointed water management committee to manage future water production, distribution, and to ensure funds are accumulated for system replacement
• Discuss / observe local crop species to ensure discarded household water can be compatible with community agriculture 
• Facilitate the extraction of water from the borehole using a local solar supplier, followed by testing in New Zealand.