Water remediation: Passive Treatment Technologies

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Bonnie Morgan
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1 Presenter: Jacques Meyer Project design: Adrian Haagner, Piet Smit & Jacques Meyer Water remediation: Passive Treatment Technologies Using a sub-surface flow wetland on a rehabilitated decommissioned coal mine in Mpumalanga, South Africa.

Treatment Technologies Using a sub-surface flow wetland on

2 Slide 2 of 21 Presentation structure Statements by researchers. Overview of passive water treatment technologies. Advantages & challenges. Problem statement: Water challenges identified on site. Remediation strategy. Motivation for selecting treatment system. Conceptual design (Chemical & Hydrological). The way forward. Questions.

Problem statement: Water challenges identified on site. Remediation strategy.

3 Slide 3 of 21 Statements These innovative technologies promote more effective, efficient clean-up, or facilitating remediation of sites that could not practicably be treated with other technologies (Doshi, 2006). Passive mine drainage systems could treat metal waste streams effectively (99% or greater removal) (Cohen, 2004). The passive bioreactor (wetland treatment system) offers a less expensive alternative to the conventional chemical precipitation technologies (Cohen, 2004). Anaerobic systems utilizing sulphate-reducing bacteria have successfully reduced sulphate, removed metals with up to almost 100% efficiency, and produced alkalinity to treat acid mine drainage (Doshi, 2006).

The passive bioreactor (wetland treatment system) offers a less expensive alternative to the conventional chemical precipitation technologies (Cohen, 2004).

4 Slide 4 of 21 Overview Definition: Improving water quality through biological & chemical processes/reactions in a controlled environment. Different types of passive water treatment systems. Selection based on influent waste water quality & end objective water quality of effluent.

Different types of passive water treatment systems.

5 Slide 5 of 21 Overview (2) Mechanisms of treatment Adsorption & complexation of metals by organic substrates. Microbial sulphate reduction, followed by metal sulphide precipitation. Precipitation of ferric and manganese oxides. Adsorption of metals by ferric hydroxides. Metal uptake by plants. Filtration of suspended and colloidal materials.

Microbial sulphate reduction, followed by metal sulphide precipitation.

6 Slide 6 of 21 Advantages & Challenges Advantages Lower cost Fewer site visits Little or no power required May utilize waste material Effective for multiple contaminants Effective in neutral, acidic, or alkaline conditions Little sludge generation Inconspicuous or natural appearance May resist freezing Easily combines with other passive treatments (Doshi, 2006) Challanges Limited to low flows or concentrations Less control over some paramters Requires some maintenance or renovation Potentially high space requirements Less technical experience Potential odor problems Low effectiveness for Mn treatment Need for polishing after treatment H 2 S production Carbon source requried

treatments (Doshi, 2006) Challanges Limited to low flows or concentrations Less control over some paramters Requires some maintenance or renovation Potentially high space

7 Slide 7 of 21 Problem statement Decant water quality (11 months of sampling) Constituents Average Concentration/value ICMA Limit ph SANS 241:2006* & 2011 Sulphate mg/l 200 mg/l 500 mg/l Iron 0.2 mg/l 0.1 mg/l 2 mg/l Manganese 2.19 mg/l 0.02 mg/l 0.5 mg/l Aluminium 0.08 mg/l 0.15 mg/l 0.3 mg/l Calcium mg/l 32 mg/l 150* mg/l Magnesium mg/l 30 mg/l 70* mg/l TDS mg/l 450 mg/l 1200 mg/l EC ms/m 40 ms/m 170 ms/m Total alkalinity mg/l - - **ICMA: Inkomati Catchment Management Agency

02 mg/l 0.5 mg/l Aluminium 0.08 mg/l 0.15 mg/l 0.3 mg/l Calcium 213.90 mg/l 32 mg/l 150* mg/l Magnesium 128.

8 Cubes per 24 H Slide 8 of 21 Problem Statement (2) Decant water quantity Oct-13 Nov-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Sampling dates Flow rate (m³/day) Expon. (Flow rate (m³/day))

9 Slide 9 of 21 Problem statement (3) Simulated TDS concentration contours 50 years into the future (2060) (modelled in 2010/2011).

10 Problem statement (4) Constituents Average Concentration/value Slide 10 of 21 Groundwater quality in pit (sampled 2014) ICMA Limit SANS 241:2006* & 2011 ph Sulphate 80 mg/l 200 mg/l 500 mg/l Iron <0.01 mg/l 0.1 mg/l 2 mg/l Manganese 2 mg/l 0.02 mg/l 0.5 mg/l Aluminium <0.01 mg/l 0.15 mg/l 0.3 mg/l Calcium 30.7 mg/l 32 mg/l 150* mg/l Magnesium 18.7 mg/l 30 mg/l 70* mg/l TDS 244 mg/l 450 mg/l 1200 mg/l EC 37.7 ms/m 40 ms/m 170 ms/m Total alkalinity 95 mg/l - - Acid generation Potentially acid generating, but sulphide sulphur is lower than expected for sustained acid generation. Pit water quality will not be worse than decant water for considerable duration.

7 mg/l 32 mg/l 150* mg/l Magnesium 18.7 mg/l 30 mg/l 70* mg/l TDS 244 mg/l 450 mg/l 1200 mg/l EC 37.

11 Slide 11 of 21 Remediation strategy Anaerobic passive water treatment system (sub-surface flow wetland) for decant Sulphate reducing bacteria. Plants (Typha capensis & Phragmites australis). Kaksonen, unknown date

12 Slide 12 of 21 Remediation strategy (2) Extraction boreholes for groundwater in pit Monitoring borehole drilled: geo-chemical characterization of backfilled material. Pump test performed. Two boreholes required to manage groundwater within pit: objective is to manage decant volume and manage groundwater plume.

backfilled material. Pump test performed.

13 Slide 13 of 21 Motivation for treatment selection Desolate site. No service-infrastructure available. Water treatment required and within treatable range for passive treatment systems. Water quality constituents not extremely elevated. Hydro-geochemical modelling indicated little/or no risk for acid generation. Maintenance & monitoring will be limited. Land to be sold to farmer after closure: grazing end land use.

Water quality constituents not extremely elevated.

14 Slide 14 of 21 Conceptual design System Borehole with wind mill Borehole with wind mill Reservoir Wetland

15 Slide 15 of 21 Conceptual design (2) Treatment components Collector trenches: Intercept groundwater and surface water run-off. Reservoir: Controlled flow. Sump: Point of organic carbon addition. Anaerobic cell: Sulphate & metals (excluding manganese). Rock filter: Manganese, bacteria, dissolved oxygen replacement. Settling pond/clear pool: Last resort treatment if required. Control flow into natural drainage system.

Anaerobic cell: Sulphate & metals (excluding manganese).

16 Slide 16 of 21 Conceptual design (3) Two design phases Chemical design: Calculate substrate volume for sufficient sulphate reduction & metal precipitation. Hydrological design: Calculate wetland size for sufficient HRT (hydrological retention time).

sulphate reduction & metal precipitation.

17 Slide 17 of 21 Conceptual design (4) Chemical design 2CH 2 O(aq) + SO H + H 2 S + 2HCO 3 2 moles of organic carbon reduces 1 mole of sulphate. Thus 60 grams organic carbon (OC) reduces 96 grams sulphate. But, sulphate reduction rate: mmol/cube OM/day. With safety factors build in: 1209 cubes required (total substrate volume). Substrate: composted cow manure, wood chips, hay, sand, mushroom compost.

Thus 60 grams organic carbon (OC) reduces 96 grams sulphate.

18 Slide 18 of 21 Conceptual design (5) Hydrological design Darcy s law: Q=KsAS Porosity: 35-60% compost-0.37 Bed depth: 1.35m Length: 30.08m Width: 29.8m Volume decant: 65 m 3 /day Hydraulic conductivity: 36 m 3 /m 2 /day Cross sectional surface: 46.7 m 2 Hydraulic head: 0.03 Total void volume: m 3 HRT: 6.8 days Wetland tank capacity: 1209 m 3 Wetland size: 0.12 ha

8m Volume decant: 65 m 3 /day Hydraulic conductivity: 36 m 3 /m 2 /day Cross sectional

19 Slide 19 of 21 Conceptual design (6) LINK TO EXCEL SHEET Site specific conceptual design of passive water treatment system.

20 Slide 20 of 21 The way forward o Conceptual design is finalised. o Civil/Engineering design in progress. o Summit to the ICMA/DWA for review and approval. o IWULA in progress (NWA, sections 21 G, F, A). o If all go well, CONSTRUCT. o Success?!

o Summit to the ICMA/DWA for review and approval.

21 Slide 21 of 21 Questions?? Thank you!

OPTIMIZING BIOLOGICAL PHOSPHORUS REMOVAL FROM AN SBR SYSTEM MIDDLEBURY, VT. Paul Klebs, Senior Applications Engineer Aqua-Aerobic Systems, Inc.

OPTIMIZING BIOLOGICAL PHOSPHORUS REMOVAL FROM AN SBR SYSTEM ABSTRACT MIDDLEBURY, VT Paul Klebs, Senior Applications Engineer Aqua-Aerobic Systems, Inc. The Middlebury Wastwater Treatment Plant, located