Water Research 39 (2005) 3587–3596 Wastewater sludge as a potential raw material for antagonistic fungus (Trichoderma sp.): Role of pre-treatment and solids concentration Mausam Verma a , Satinder K. Brar a , R.D. Tyagi a,Ã , J.R. Vale´ro a , R.Y. Surampalli b a INRS-ETE, Universite´du Que´bec, 490, Rue de la Couronne, Que´bec, Canada G1K 9A9 b US EPA, P.O. Box 17-2141, Kansas City, Kansas, KS 66117, USA Received 27 February 2005; received in revised form 29 June 2005; accepted 1 July 2005 Available online 10 August 2005 Abstract Feasibility of production of antagonistic Trichoderma sp. conidial spores using wastewater sludge as a raw material employing different suspended solids concentration (10–50 g/l) was investigated in shake flasks. Maximum conidial spore count obtained for raw sludge was 1.98  10 4 CFU/ml, which was enhanced by sludge pre-treatments (alkaline and thermal alkaline). Conidial spore count ranging from 1.3  10 6 to 2.8  10 7 CFU/ml was observed for alkaline and thermal alkaline treated sludges. Optimal suspended solids concentration was 30 g/l (10 7 CFU/ml) whereas, lower (o20 g/l) and higher (430 g/l) solids concentration were less efficient. Thermal alkaline pre-treated sludge showed diauxic growth due to multiplicity of sludge biodegradability. A simple, modified CFU filtration technique was also developed for fungal spore assessment in sludge. Bioassay of fermented sludge against spruce budworm larvae showed entomotoxicity (15036 SBU/ml), on par with Bacillus thuringiensis biopesticides. This study successfully demonstrated potential of wastewater sludge as a raw material for production of value added product, aiding in sludge management and proliferation of eco-friendly and economical biocontrol agents. r 2005 Elsevier Ltd. All rights reserved. Keywords: Biocontrol agent; Conidia; Entomotoxicity; Pre-treatment; Solids; Trichoderma viride; Wastewater sludge 1. Introduction Trichoderma-based biocontrol agents (BCAs) possess an added ability of plant growth promotion and soil remediation activities compared to their counterparts (virus, bacteria, nematodes, and protozoa) (Harman et al., 1993; Esposito and da Silva, 1998). Their capability to synthesize antagonistic compounds (proteins, enzymes, and antibiotics) and micronutrients (vitamins, hormones and minerals) enhance their biocontrol activity. Akin to other fungal BCAs, conidial mass of Tricho- derma is most proficient propagule, which can tolerate downstream processing (e.g. air drying) (Amsellem et al., 1999). Despite the advantages, mass production of Trichoderma BCAs is less prevalent owing to high-cost raw materials like Mendel’s medium, molasses–corn steep liquor, sodium tartrate (10 6 –10 7 CFU/ml or, CFU/g ARTICLE IN PRESS www.elsevier.com/locate/watres 0043-1354/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2005.07.001 Ã Corresponding author. Institut Nationale de la Recher che Scientifique; Eau, Terre et Environment, 2800, Rue Einstein, C.P. 7500 Sainte Foy, Sainte-Foy, Que., Canada G1V4C7. Tel.: +1 418 654 2617; fax: +1 418 654 2600. E-mail addresses: tyagi@ete.inrs.ca, tyagi@inrs-ete.uquebec.ca (R.D. Tyagi).