Quality of organic fertilizer obtained through vermicomposting of sewage sludge with earthworm (Eisenia foetida)

The purpose of this research was to determine the quality of organic fertilizer obtained through vermicomposting with earthworms (Eisenia foetida Sav.) in sludge from stabilization ponds in the city of Juliaca. Thirty-one samples were randomly collected in each of the eight lagoons, divided into nine experimental units and three groups with three random replicates, T1 (sludge + manure + earthworm), T2 (sludge + earthworm) and T3 (sludge). Consecutively, biomass, number of worms, and color were analyzed as indicators of transformation of sludge into compost, on a monthly basis for 3 months. In T1 the biomass increased in the three months, while in T2 a slight gain was shown. Regarding the number of worms, T1 doubled the initial amount and T2 showed mortality in the first month, but in the last month it reached 130. The color in T1 was the only one that reached the 10YR 2/1 shade, followed by T2. In addition, the percentage of pathogen removal and macronutrient content were estimated after 3 months. In this sense, pathogens reported significant differences in the percentage of removal for each treatment, with T1 being the best treatment, followed by T2 and T3: In the macronutrient content, significant differences were also observed between treatments, where T1 presented higher concentration in nitrogen, potassium and calcium as opposed to T2 and T3. In the case of phosphorus, T2 presented a higher percentage. It was demonstrated that earthworms in this type of sludge accelerate the removal of pathogenic agents improving its quality, turning it into a quality organic fertilizer due to the improvement in the content of microbiological agents, increase in macronutrients and positive adaptation of the earthworms. This is beneficial for the use of the sludge for gardening, tall stem crops and reforestation as recommended in regulations for the reuse of sludge generated in wastewater treatment plants.