TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In (M1), the pH of the aqueous solution is increased and/or decreased to obtain a pH of approximately 8.0-10.0 or near 9.15+/-0.5. The aqueous solution is waste sludge from a drinking water and/or wastewater purification facility. The aqueous solution comprises a catalyst. The metal(s) comprise any one of aluminum, iron, calcium, magnesium or its combination. The metal(s) is mostly aluminum. The biological reaction comprises fermentation-raised bacteria, which is non-pathogenic bacteria, or selectively cultured bacteria. The biological reaction comprises a biological culture chosen from Acinobacter, Nitrobacter, Enterobacter, Thiobacillus and T.denitrificans, Pseudomonas, Escherichia, Arthrobacter, Achromobacter, Bdellovibrio, Thiobacterium, Macromonas, Bacillus, Corynebacterium, Aeromonas, Alcaligenes, Flavobacterium, Vibrio, fungi and their combination. The biological reaction is mesophilic or thermophilic and/or the biological reaction comprises mesophilic or thermophilic bacteria, or the biological reaction comprises psychrophiles or psychrotrophs. (M1) further involves adding nutrients to the biological reaction. The nutrient(s) comprise any one of ammonia, phosphoric acid, ammonium hydroxide, urea, nitrogen salts, phosphate-carbon compounds, nitrogen phosphate salts, nitrogen-carbon compounds, nitrogen-carbon polymers, nitrogen-phosphate-carbon compounds, nitrogen-phosphate-carbon polymers and their combination. The pH is increased by the addition of a base, and reduced by the addition of an acid. The base comprises a polymer, compound or salt which is an electron donor or which contains an OH moiety. The base comprises a Group I or Group II A metal oxide and/or hydroxide. The base comprises any one of sodium hydroxide, magnesium hydroxide, magnesium oxide, calcium hydroxide, calcium oxide, potassium hydroxide and their combination. The acid comprises a salt, compound or polymer, which is an electron acceptor. The acid preferably comprises halogen anion, an inorganic salt anion or carbonic acid. The liquid/solids separation is performed by coagulating the bacteria from the biological reactor with a cationic organic polymer, or by coagulating the metals in a metal oxide and/or metal hydroxide form(s) with an anionic polymer. The cationic polymer comprises cationic nitrogen moiety, which is quaternized, or acrylamide. The anionic polymer comprises an acidified moiety based upon an acrylate and/or an acrylic moiety, or acrylamide. The metal(s) are recycled to manufacture a coagulant which is in a salt form having a pH of less than approximately 4.0, or in the form of a polynuclear aluminum compound, which has a temperature history of greater than 100degreesC. In (M1), after biological reaction the aqueous solution comprises a disinfectant. The bacteria from the biological reactor are treated according to the US EPA 503 regulations. The bacteria are digested in a thermophilic digester. EXAMPLE - No relevant example is given.