Proposed eutrophication management strategy

25 February 2011

Eutrophication (see elsewhere on this blog) is the commonest and most severe impact that Man exerts on the quality of our water resources. Harmful algal blooms (HABs) are the commonest symptom of this abuse. Nearly half of South Africa’s water resources are impacted by eutrophication, a problem that has been willfully ignored in this country for thirty years.

This situation, whereby we have been forced to live with the problem, needs to be changed before it degrades our social and economic future any further. It will take a long time and it will cost a lot, but it is undeniably necessary now.  We can no longer afford the luxury of spending money on studies of harmful algae or on trying to predict when problematical algal blooms will occur.  We know what causes the problem, it is time to address the cause, not the symptoms!

Adoption of the following primary ten point strategy will reverse the sustained disposal of nutrient-rich effluents to our rivers and dams.  It will take at least 15 years before meaningful improvements are evident!

1. The effluents from all wastewater treatment works should, within five years, comply with the 1 mg per liter phosphorus standard (see Note 1). Where specific reductions, requiring more stringent treatment, have been identified then these must prevail (e.g Harding, 2008). Incentives should be sought whereby effluents can be productively utilized so as to reduce the pollution of surface waters.

2. Phosphorus budgets (e.g Harding 2008) should be compiled for all dams within five years. Catchment-based load reductions, necessary to meet these budgets, should be established on a priority basis within a further ten years.

3. Laundry detergents containing phosphorus should be replaced with phosphate-free equivalents by 2015.

4. Eighty percent of the suspended solids load in urban runoff should be removed by simple sedimentation. This will effectively remove between fifty and seventy percent of the phosphorus – and other pollutants – contained in this form of runoff. As is already the case in Cape Town, this requirement should be mandatory for all new developments.

5. In cases where dams contain phosphorus rich sediments that form a significant fraction of the phosphorus budget, dredging or in situ chemical inactivation should be implemented.

6. Agricultural sources of nutrients to surface waters should be aggressively managed using financial incentives.

7. Runoff from informal settlements should be intercepted and treated using retention ponds and floating wetland technologies (see Note 2).

8. Targeted performance monitoring of all implementations attenuating the movement of excess nutrients to surface waters.

9. Rollout of a sustained national information program that explains the need for the prevention of eutrophication.

10. Formulation and implementation of a tertiary-level skills training program, supported by specialist mentoring of technical support personnel.  This recommendation has been on offer to the national regulator since 2004.

Note 1: Although the 1 mg per liter P standard is an imperfect tool, it is an existing standard that can (a) be implemented quickly and (b) provide a significant level of improvement in many cases. The intention is for it to be replaced by the catchment load based approach.

Note 2: These technologies provide an immediately available and proven means of removing nutrients and sequestering heavy metals and pharmaceuticals.

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