Sludge Happens

Louise Heffernan Metropolitan Council Environmental Services Empire Wastewater Treatment Plant Anaerobic Digester Pilot Project

Empire wastewater facility Dewaterability issues Designed to produce cake solids content~16-18% Recent years ~ 11-12% Storage pad usage, hauling and land application Impacts operational costs Introduction

Empire current operations  11% cake – $310,000/year land application cost Target operations  18% cake – $200,000/year land application cost Why does this matter?

Empire WWTP, Empire Township Biosolids Pad

Evaluate treatment options Improve dewaterability Establish stable pilots Monitor performance Gather data Analyze system results Examine methods to achieve target cake Implement at the Empire WWTP Purpose

Bacteria only make up % of the organic matter mass in a floc Most of the remainder is biopolymer (protein and polysaccharides) Biofloc Makeup Higgins, 2012

Chemical conditioning prior to BFP Alter biomass matrix Good floc formation and settling DCB negatively charged biopolymers Lower soluble P Chemical Addition Treatments

Current practice at Empire  WAS is thickened, accounts for 50% digester feed  Not stored at any point S.T.WAS treatment  Unaerated storage of WAS prior to thickening  Allows time for P, K, Mg release  Removal prior to digestion Research suggests dewatering ability linked to cation concentration Stored/Thickened WAS Treatment

Pilot Test Variables Pilot # 1 : Stored/Thickened WAS (S.T.W.A.S.)  Unaerated storage > 4 days Pilot # 2 : Chemical addition (FeCl3) Pilot # 3 : Control Pilot # 4 : Chemical addition (MgCl2)

Pilot Digesters 2013

Results/Analysis

Empire has low cake solids (11-12%) Potential methods to improve dewaterability investigated System will continue to run past 3 SRTS Results from 2013 pilot digesters:  Stability was achieved  All treatments showed decrease in soluble P and K  All treatments showed increase in cake solids  Dewatering performance below target values Summary and Conclusions

Must investigate more alternatives to achieve 18% Future option: STWAS & chemical addition Thermal pretreatment technologies Other chemicals  Mg(OH)2 Recommendations

My Experience Networking opportunities Communicate with wide range of professionals Great educational experience Met Council tours Lead into independent study

Questions?