Nitrate removal from wastewater generated in wet Flue Gas Desulphurisation Systems (FGD) in coal-fired power generation using the heterotrophic denitrification method

Krzysztof Iskra; Łukasz Krawczyk; Jan M. Miodoński; Dominika Wierzbicka-Kopertowska

doi:10.2478/oszn-2020-0012

Figures & Tables

Diagram of the installation for conducting the denitrification process: ZŚ - raw wastewater tank, ZO - treated wastewater tank, ZD - denitrification bed, Q - wastewater flow measurement, α - denitrified effluent recirculation pump, pH - pH measurement, NO3 - nitrate measurement, T - temperature measurement, RedOx - measurement of oxidoreductive potential

Changes in nitrate and COD concentration in wastewater from wet FGD unit

Nitrate nitrogen removal rate apposed its loading rate at the reactor inflow during the studies

Effect of active surface loading rate on efficiency (% removal)

The wet FGD wastewater characteristics during the studies

Item.	Feature/indicator tested	Unit	Wastewater batch no.				Mean
Item.	Feature/indicator tested	Unit	I	II	III	IV	Mean
1	pH value	-	8.84	8.87	8.57	7.47	-
2	BOD₅	gO₂/m³	0.73	0.87	1.11	1.39	1.0
3	COD	gO₂/m³	209	213	246	222	222.5
4	Total nitrogen (N_total)	gN/m³	233	68.2	87.7	101.9	122.7
5	Kjeldahl nitrogen (TKN)	gN/m³	43.2	21.9	35.9	0.97	25.5
6	Ammonium nitrogen (N-NH₄)	gN/m³	30.5	14.9	19.6	0.62	16.4
7	Nitrate nitrogen (N-NO₃)	gN/m³	185.2	53	58	100.9	99.3
8	Nitrite nitrogen (N-NO₂)	gN/m³	4.61	0,84	1.1	0.03	1.6
9	Total phosphorus (P)	gP/m³	7.5	5.73	1.7	-	5.0
10	Orthophosphates (P-PO₄)	gP/m³	0.043	0.18	0.07	0.03	0.1
11	Total suspended solids (TSS)	g/m³	422	392	212	69	273.8
12	Chlorides (Cl⁻)	g/m³	35400	19200	18500	16000	22275.0
13	Sulphates (SO₄²⁻)	g/m³	1186	1100	1227	-	1171.0

The summary of methods used for wet FGD wastewater treatment

Item.	Method name	Major advantages	Major disadvantages	Nitrate removal
1	2	3	4	5
1	Simplified methods	Operation does not require qualified service Resilience to changes in the FGD technology	Large area required for use of lagoons for wastewater / sediment disposal	No
2	Chemical methods	Small installation volume (short time chemical reaction) Technology with a wide range of both customization and control strategy options	High demand for chemical reagents	No
Biological methods
3	Treatment reactors	Lower maintenance costs compared to chemical methods Consuming less chemical reagents	Operation requires qualified staff Small resilience to changes in wastewater composition	Yes
4	Hydrophyte wastewater treatment plants	Possibility of achieving parameters similar to those for treatment reactors	Large area required Significant reduction in the efficiency of wastewater treatment at low temperatures	Yes
Physical methods
5	Evaporative methods	A significant reduction in the amount of generated wastewater	High maintenance costs of concentrating wastewater on evaporators	No
6	Membrane methods	Lower maintenance costs compared to evaporative methods	The need for frequent flushing of membranes High risk of precipitation of mineral salts on the surface of membranes (fouling) High investment costs	Yes¹
7	Ion exchange methods	In the case of an existing ion exchange installation at the facility, the extension will take lower investment costs	Need for frequent ionites regeneration Higher efficiency of sulphate ion exchange than nitrate ion	Yes

Nitrate removal from wastewater generated in wet Flue Gas Desulphurisation Systems (FGD) in coal-fired power generation using the heterotrophic denitrification method

Figures & Tables

Figure 1

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Figure 3

Figure 4

The wet FGD wastewater characteristics during the studies

The summary of methods used for wet FGD wastewater treatment

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