USE PF URBAN SLUDGE COMPOST AS FERTILIZANT ON APPLE ORCHARDS

This study shows the influence of compost fertilization derived from sludge obtained from wastewater treatment on the nutrition of an eight-year-old apple orchard, ʹJonathanʹ cv. A field experiment was conducted to demonstrate the beneficial and negative aspects of (urban) sludge compost fertilization in apples and to assess the risk of soil contamination with heavy metals from municipal sewage sludge compost. The experimental factor was the compost with the following gradations: V1 = 0 t/ha, V2 = 20 t/ha, V3 = 40 t/ha, V4 = 60 t/ha, V5 = 80 t/ha. After two years (2019-2021) from soil fertilization with compost, the nitrogen content of the leaves increased in the treatment with the maximum fertilization dose (80 t/ha) by 30% compared to the unfertilized control, while the phosphorus content of leaves increased by 80% compared to non-fertilization control. The potassium content of the leaves increased by 36% in the 80 t/ha treatment compared to the unfertilized control, but still remained at a deficit level. The results showed that growth and yield were improved by using sewage sludge compost. However, sewage sludge compost applications have not significantly altered the heavy metal content of plant tissues. The concentration of heavy metals in the soil did not exceed the maximum permissible thresholds according to standards established in other EU countries, where compost from sewage sludge is considered product, not waste. However, the calculation of the Igeo index (geoaccumulation index of heavy metal in soil) showed certain levels of soil pollution already installed with Cd Zn, Pb in all variants fertilized with compost.

Improving sewage sludge compost process and quality by carbon sources addition

In present study, the effects of carbon sources on compost process and quality were evaluated in the lab-scale sewage sludge (SS) composting. The composting experiments were performed for 32 days in 5 L reactors. The results showed that carbon sources could change the nitrogen conversion and improve the compost quality. Especially, the readily degradable carbon source could promote organic matter degradation, improve nitrogen conversion process and accelerate compost maturation. The addition of glucose and sucrose could increase dissolved organic carbon, CO2 emission, dehydrogenase activity, nitrification and germination index during the SS composting. That's because glucose and sucrose could be quickly used by microbes as energy and carbon source substance to increase activity of microbes and ammonia assimilation. What's more, the NH3 emission was reduced by 26.9% and 32.1% in glucose and sucrose treatments, respectively. Therefore, the addition of readily degradable carbon source could reduce NH3 emission and improve compost maturity in the SS composting.

Evaluation of Yield and Quality Attributes of Grafted Brinjal under Treated Paperboard Mill Effluent Irrigation and Sludge Application

Field experiment was conducted to assess the impact of paperboard mill sludge compost and treated paperboard mill effluent irrigation on growth and yield of grafted brinjal. Among the different treatment combinations, application of phosphorus enriched ETP sludge compost at 5 t ha-1 along with treated effluent through drip irrigation and recommended level of NPK (200:150:100 kg NPK ha-1) resulted the highest brinjal yield of 42.7 t ha-1. There were no adverse effects on soil properties due to sludge compost application and treated effluent irrigation. Quality attributes of the fruits which include anthocyanin content, total phenol content, ascorbic acid content, titrable acidity and protein content were not affected due to the composted sludge application along with treated effluent irrigation. Thus, the treated effluent and the composted sludge which complies with the state pollution control board norms can be used as a viable alternative source of irrigation and nutrients for grafted brinjal cultivation without adversely affecting on crop quality.