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This study characterises the sewage sludge from 26 sewage treatment plants in India, which demonstrates the nutrient potential and highlights the associated challenges in using the sludge. The dry sludge had 2.35%–4.2% N, 2.46–3.2% phosphorus (P2O5) and 0.83%–1.24% potassium oxide (K2O), whereas sludge ash contains ~13.6% and 2.7%, P2O5 and K2O, respectively. Total nutrient potential from the sludge of the existing sewage treatment facility was 97.5 × 103 tonne/year, which is equivalent to 0.92% urea or 0.19% NPK used presently as conventional fertilisers in India. However, pre‐treatment may be required for this sludge before using it in agricultural fields as heavy metals, such as Zn, Cu, Ni, Cd, and Cr, were found higher than the compost standards. This study would be useful for the researchers and policymakers globally and would motivate them to make policies and deploy suitable technologies towards the nutrient utilisation from sewage sludge. [ABSTRACT FROM AUTHOR]

There has been a ton of debate on developing goals and the conflicts regarding environmental preservation. In the wastewater treatment industry, biochar seems to appear as a low-cost and environmentally friendly alternative because of its high porosity and adsorbent capacity. This study used the Scopus database to map articles on the topic through a systematic methodology and screening. The results demonstrate the approach researchers are giving to biochar adsorbing characteristics. It was observed that research about biochar applied to wastewater is recent and shortage. China and India were the countries that most published about it. Sewage sludge was the most common biomass used for biochar production, and pyrolysis temperature remained mainly at 300° C to 700 °C. Also, the removal of heavy metals was the greater purpose of the studies. Finally, this mapping described biochar formation and its use as an adsorbent for wastewater treatment purposes, providing important data for directing future studies. [ABSTRACT FROM AUTHOR]