Results from different research suggest that metallic iron (Fe⁰) materials enhance anaerobic digestion (AD) systems to remove organics (chemical oxygen demand (COD)), phosphorus and nitrogen from polluted water. However, the available results are difficult to compare because they are derived from different experimental conditions. This research characterises the effects of Fe⁰ type and dosage in AD systems to simultaneously remove COD and nutrients (orthophosphate (PO₄³⁻), ammonium (NH₄⁺), and nitrate (NO₃⁻)) Lab-scale reactors containing domestic sewage (DS) were fed with various Fe⁰ dosages (0 to 30 g/L). Batch AD experiments were operated at 37 ± 0.5 °C for 76 days; the initial pH value was 7.5. Scrap iron (SI) and steel wool (SW) were used as Fe⁰ sources. Results show that: (i) SW performed better than SI on COD and PO₄³⁻ removal (ii) optimum dosage for the organics and nutrients removal was 10 g/L SI (iii) (NO₃⁻ + NH₄⁺) was the least removed pollutant (iv) maximum observed COD, PO₄³⁻ and NO₃⁻ + NH₄⁺ removal efficiencies were 88.0%, 98.0% and 40.0% for 10 g/L SI, 88.2%, 99.9%, 25.1% for 10 g/L SW, and 68.9%, 7.3% and 0.7% for the reference system. Fe⁰-supported AD significantly removed the organics and nutrients from DS.

Science denial relates to rejecting well-established views that are no longer questioned by scientists within a given community. This expression is frequently connected with climate change and evolution. In such cases, prevailing views are built on historical facts and consensus. For water remediation using metallic iron (Fe⁰), also known as the remediation Fe⁰/H₂O system, a consensus on electro-chemical contaminant reduction was established during the 1990s and still prevails. Arguments against the reductive transformation concept have been regarded for more than a decade as ‘science denial’. However, is it the prevailing concept that denies the science of aqueous iron corrosion? This article retraces the path taken by our research group to question the reductive transformation concept. It is shown that the validity of the following has been questioned: (i) analytical applications of the arsenazo III method for the determination of uranium, (ii) molecular diffusion as sole relevant mass-transport process in the vicinity of the Fe⁰ surface in filtration systems, and (iii) the volumetric expansive nature of iron corrosion at pH > 4.5. Item (i) questions the capability of Fe⁰ to serve as an electron donor for U^VI reduction under environmental conditions. Items (ii) and (iii) are inter-related, as the Fe⁰ surface is permanently shielded by a non-conductive oxide scale acting as a diffusion barrier to dissolved species and a barrier to electrons from Fe⁰. The net result is that no electron transfer from Fe⁰ to contaminants is possible under environmental conditions. This conclusion refutes the validity of the reductive transformation concept and calls for alternative theories.

In Tanzania, inadequate access to water affects 26% of urban and 38% of rural populations, who depend on piped water systems and are often subject to rationing. Low-income households face the significant burden of high water bills and (sometimes) poor water quality. Alternative water sources such as gravity-fed, rainwater harvesting, and drilled well systems are often overlooked, primarily due to the absence of evaluations based on engineering economic equivalence (EEE) principles that determine their viability due to prioritization. This study addresses this gap by analyzing existing literature and utilizing data from Mbeya City, focusing on households relying on tap water, rainwater harvesting, and drilled wells. Engineering Economic Equivalency computations were used to assess the present worth of these water sources, with values determined at Tshs 11,009,424/- for tapped water systems, Tshs 10,283,000/- for rainwater harvesting, and Tshs 12,099,940/- for drilled wells. While rainwater harvesting appears cost-effective, it was found unsuitable for drinking, and tapped water systems incur variable consumption costs. Consequently, the drilled well system is the most sustainable option for ensuring reliable household water access. Households in Mbeya are urged to deploy the engineering economic equivalence principle to prioritize their water-for-own-use.

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