2.10 Adequacy in the context of emergency

Planted gravel filters can be found in various emergency settings. Their appropriateness depends on specific factors and the nature of the emergency.

The filter system is easy to set up but requires a relatively large footprint per volume treated, which can be a limitation. The vertical planted gravel filter could be the preferred solution due to its lower space requirement than horizontal planted gravel filters, but it is more complex to install and manage.

While the construction phase can take up to one month, the start-up phase usually takes two months to establish plants and microorganisms. It can take up to 6 months to achieve desired removal efficiencies. Therefore, the PGFs are unsuitable for the acute response phase but effective during the stabilisation and recovery periods and as a long-term solution.

Effective pre-treatment is critical to preserving the filter’s functionality and longevity. The filter system can be scaled up depending on space availability, although large-scale filter systems must be divided into smaller beds with alternating use to ensure performance. For vertical filter systems, it is necessary to respect batch feeding, carry out annual cleaning of the upper sludge layer, and control and clean the pipes and distribution systems.

For economic viability, it is essential to source materials locally whenever possible. This includes locally available materials such as liners, foils, and gravel. Utilising local resources can help reduce costs and make the project more financially sustainable.

Disaster resilience can also be considered during installation; for example, raised walls protecting the plant from surface water flooding and simple excavated bunds for seismic reinforcement can be realised.