WATER MANAGEMENT
CLEAN WATER FOR GENERATIONS TO COME
Water management plan and water audits
Segregation of water Streams
Minimisation of hydrocarbon contamination of process water
Adequate drainage infrastructure
Reuse and/or recycling of water
Waste water treatment
With experience preparing permit applications and delivering compliance solutions for regulations and requirements, authority-specific programs, and water quality rules, SCS-TECHNOLOGY perform cost-effective control technology assessments and compliance plans that meet regulatory requirements.
Optimization projects for waste water management include prevention, collection and separation waste water types, maximising internal recycling and using an adequate treatment for each final flow. This includes techniques utilising, e.g. oil interceptors, filtration or sedimentation. In this context, the following techniques can be used where the prerequisites mentioned are present:
avoiding the use of potable water for production lines
increasing the number and/or capacity of water circulating systems when building new plants or modernising/revamping existing plants
centralizing the distribution of incoming fresh water
using the water in cascades until single parameters reach their legal or technical limits
using the water in other plants if only single parameters of the water are affected and further usage is possible
keeping treated and untreated waste water separated; by this measure it is possible to dispose of waste water in different ways at a reasonable cost
using rainwater whenever possible
SCS-TECHNOLOGY has been working with many of its clients over the course of decades, assisting with multiple generations of plans and strategies. In the end, we can assist you in any water-related project, large or small.
Water management plan and water audits
A water management plan and water audits are part of the Environmental Management System and includes:
flow diagrams and a water mass balance of the plant
establishment of water efficiency objectives
implementation of water optimization techniques (e.g. control of water usage, water recycling, detection and repair of leaks)
Water audits should be carried out at least annually.
Segregation of water Streams
Each water stream (e.g. surface run-off water, process water) should be collected and treated separately, based on the pollutant content and on the required treatment techniques. In particular, uncontaminated waste water streams are segregated from waste water streams that require treatment.
Monitoring & Reporting
The regulations for Clean Air, Clean Water as well as for Resource Conservation and Recovery define environmental requirements on facility owners and operators. The regulations along with permit requirements regularly change and becoming stricter. Beyond it is important to remain compliant. SCS-TECHNOLOGY provide air, surface water, groundwater, and other environmental monitoring and reporting services for sites.
Minimisation of hydrocarbon contamination of process water
The contamination of process water by oil and lubricant losses can be minimized by using techniques such as:
oil-tight bearings and bearing seals for working rolls
leakage indicators
regular inspections and preventive maintenance
In order to reduce the load of organic pollutants in water contaminated with oil or grease (e.g. from oil spillages or from the cleaning of rolling and tempering emulsions, degreasing solutions and wire-drawing lubricants) that is sent to further treatment, best available technique is to separate the organic and the aqueous phase.
Adequate drainage infrastructure
The process areas should be connected to drainage infrastructure. Contaminated process water should be collected in the drainage infrastructure along with washing water and occasional spillages and sent to treatment.
Reuse and/or recycling of water
Water streams (e.g. effluents from wet scrubbing or quench baths) should be reused and/or recycled, if necessary after treatment. The degree of water reuse and/or recycling is limited by the water balance of the plant, the content of impurities and/or the characteristics of the water streams.
Reverse cascade rinsing
Rinsing should be carried out in two or more baths in series where the flow of the rinsing water is countercurrent to the feedstock flow.
Recycling of rinsing water
After pickling or degreasing, rinsing water should be recycled to the preceding process baths as make-up water or, if appropriate, for acid recover.
Treatment and reuse of oil- and scale-bearing process water
Oil- and scale- bearing waste water should be treated separately using a sequence of cleaning steps including scale pits, settling tanks, cyclones and filtration to separate oil and scale and to reuse a large proportion of the treated water in the process.
Waste water treatment
In order to reduce emissions to water, best available technique is to treat waste water using a combination of the techniques as follows:
Preliminary, primary and general treatment, e.g.
Equalisation (All pollutants)
Neutralisation (Acids, alkalis)
Physical separation, e.g. screens, sieves, grit separators, grease separators, hydro-cyclones, oil-water separation or primary settlement tanks (Gross solids, suspended solids, oil/grease)
Physical-chemical treatment, e.g.
Adsorption (Adsorbable dissolved non-biodegradable or inhibitory pollutants, e.g. hydrocarbons, mercury)
Chemical precipitation (Precipitable dissolved non-biodegradable or inhibitory pollutants, e.g. metals, phosphorus, fluoride)
Chemical reduction (Reducible dissolved non-biodegradable or inhibitory pollutants, e.g. hexavalent chromium)
Nanofiltration/reverse osmosis (Soluble non-biodegradable or inhibitory pollutants, e.g. salts, metals)
Biological treatment, e.g.
Aerobic treatment (Biodegradable organic compounds)
Solids removal, e.g.
Coagulation and flocculation
Sedimentation
Filtration (e.g. sand-filtration, micro-filtration, ultra-filtration)
Flotation
Examples in the steel industry
Sinter Plants
Optimization projects for sinter plants includes minimizing water consumption by recycling cooling water as much as possible unless once-through cooling systems – depending on water availability – are used. Furthermore the treatment of effluent water from sinter plants where rinsing water is used or where a wet waste gas treatment system is applied, with the exception of cooling water prior to discharge by using a combination of the following techniques:
heavy metal precipitation
neutralisation
sand filtration
Pelletisation Plants / DRI (direct-reduced-Iron) Plants
Optimization projects for pelletizing plants, DRI plants includes minimizing the water consumption and discharge of scrubbing, wet rinsing and cooling water and reuse it as much as possible. Furthermore the treatment of effluent water prior to discharge by using a combination of the following techniques:
neutralisation
flocculation
sedimentation
sand filtration
heavy metal precipitation
Coke oven plants
Optimization projects for coke oven plants includes minimizing and reuse quenching water as much as possible. Furthermore state of the art is to avoid the reuse of process water with a significant organic load (like raw coke oven waste water, waste water with a high content of hydrocarbons, etc.) as quenching water. Additionally best available techniques is to pretreat waste water from the coking process and coke oven gas (COG) cleaning prior to discharge to a waste water treatment plant by using one or a combination of the following techniques:
using efficient tar and polycyclic aromatic hydrocarbons (PAH) removal by using flocculation and subsequent flotation, sedimentation and filtration individually or in combination
using efficient ammonia stripping by using alkaline and steam
Pre-treated waste water from the coking process and coke oven gas (COG) cleaning are treated in biological waste water treatment with integrated denitrification/nitrification stages.
Blast furnaces
Optimization projects for water consumption and discharge from blast furnace gas treatment includes minimising and to reuse scrubbing water as much as possible (closed loop water circulation systems), e.g. for slag granulation, if necessary after treatment with a gravel-bed filter. Additionally best available technique for treating waste water from blast furnace gas treatment is to use flocculation (coagulation) and sedimentation and the reduction of easily released cyanide, if necessary.
Basic oxygen furnaces
Optimization projects includes prevention or reduce water use and waste water emissions from primary dedusting of basic oxygen furnace (BOF) gas by using one of the following technique:
dry dedusting of basic oxygen furnace (BOF) gas;
minimising scrubbing water and reusing it as much as possible (e.g. for slag granulation) in case wet dedusting is applied
Additionally best available technique is to minimise the waste water discharge from continuous casting by using the following techniques in combination:
the removal of solids by flocculation, sedimentation and/or filtration
the removal of oil in skimming tanks or any other effective device
the recirculation of cooling water and water from vacuum generation as much as possible
Electric arc furnaces
Optimization projects includes minimising the water consumption from the electric arc furnace (EAF) process by the use of closed loop water cooling systems for the cooling of furnace devices as much as possible unless once-through cooling systems are used. Additionally best available technique is to minimise the waste water discharge from continuous casting by using the following techniques in combination:
the removal of solids by flocculation, sedimentation and/or filtration
the removal of oil in skimming tanks or any other effective device
the recirculation of cooling water and water from vacuum generation as much as possible