Date of Award:

2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Civil and Environmental Engineering

Advisor/Chair:

Dr. David K. Stevens

Abstract

Dairy processing waste (DPW) can cause many environmental problems if not treated well. Various wastewater treatment technologies have been applied to reduce the organics and inorganics in DPW. The overall objective of this research was to develop cost effective anaerobic digestion technology for hydrogen and methane production from DPW. This search included three phases of studies.

In phase 1, we investigated continuous fermentations of algae, lawn grass clippings and DPW, commingled and digested in duplicate 60 L and 3,800 L Induced Bed Reactor (IBR) anaerobic digesters at mesophilic conditions in trials that went for about two years. The goal was to commingle municipal waste in such a way that no pH control chemicals would be required. The research also yielded information about solids loading rate (SLR), efficiency of chemical oxygen demand (COD) and solids removal and biogas production. Under the conditions of the study, commingling algae or grass with DPW made it possible to avoid the addition of pH control chemicals.

In phase 2, we investigated the effects of pH, temperature, and hydraulic retention time (HRT) and organic loading rate (OLR) on hydrogen production from DPW in semicontinuous 60 L pilot IBR. Results show pH played a key role on hydrogen production and the optimal pH range was 4.8-5.5. Digestion under thermophilic temperatures (60 °C) had advantages of gaining higher hydrogen yield and suppressing the growth of methanogens. The optimal OLR was 32.9 g-COD/l-d at HRT of 3 days. Under optimal conditions, highest hydrogen yield was 160.7 ml/g-COD removed with 44.6% COD removal.

In phase 3, a mathematic model was built and implemented in R based on Anaerobic Digestion Model No. 1 (ADM1) for predicting and describing the anaerobic hydrogen production process. The modified ADM1 was then validated by comparing the predictions with observations of anaerobic hydrogen production from dairy processing waste. The model successfully predicted hydrogen production, hydrogen content, methane content, VFA concentration, and digestion system stability. This study provides a useful mathematical model to investigate anaerobic hydrogen production process and stability.

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Available for download on Friday, January 01, 2021

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