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Sunday, January 18, 2009

The treatment of hospital wastewater: an appraisal

Health Stream Literature Summary - Issue 46 - June 2007
The treatment of hospital wastewater: an appraisal

Pauwels, B. and Verstraete, W. (2006) Journal of Water & Health, 4 (4) 405-416.
 
Hospitals discharge large amounts of chemicals and microbial agents into wastewater. Chemicals discharges include pharmaceuticals, iodinated X-ray contrast media (ICM: used for X-ray imaging of soft tissues), antibiotics and disinfectants. Hospitals also discharge antibiotic resistant bacteria, viruses and maybe even prions etc. While some of these contaminants are unique to hospital settings, many are also present in sewage from domestic residences. Many of the chemical compounds are resistant to wastewater treatment and may end up in surface water where they may influence the aquatic ecosystem and interfere with the food chain. This may also pose a risk of human exposure through drinking surface water. This paper examines the issue of hospital wastewater and whether there is a case to justify separation of some or all hospital waste from the normal sewage stream.
 
The most important chemicals in hospital wastewater are antibiotics, cytostatic agents, anaesthetics, disinfectant, platinum, mercury, rare earth elements (gadolinium, indium, osmium) and iodinated X-ray contrast media. Other pharmaceuticals which have been found in wastewater treatment plant (WWTP) effluents include lipid regulators, analgesics, antibiotics, antidepressants, antiepileptics, antineoplastics, antipyretics, antiphlogistics, antirheumatics, ß-blockers, broncholytics, ß2-sympathomimetics, estrogens, secretolytics, vasodilators and X-ray contrast media.
 
Of the antibiotics used for human purposes in Europe , 26% are used in hospitals. These antibiotics and their metabolites are excreted with urine and faeces and end up in WWTP. Efforts are being made to evaluate the risk of antibiotics however there is a lack of concentration level data in hospital wastewater. For each medical treatment about 100g of X-ray contrast media is used. This represents about 30g of absorbable organic iodinated compounds (AOI). The AOI are biologically inert and stable toward metabolism during their passage through the body. They are excreted almost completely within a day after administration and end up in the WWTP where they are not well removed. As not much is know about their fate and long term effects, there is a risk associated to their spread in the environment. Particularly of interest are oestrogens. A UK study observed the feminisation of male caged fish at discharge sites of WWTPs. On a daily basis, women excrete on average approximately 32, 14 and 106 microg of conjugate estrone (E1), estradiol (E2) and estriol (E3), respectively. Pregnant women excrete about 100 times this amount. Hospital wastewater probably has elevated concentrations of E1, E2 and E3, however hospital wastewater oestrogen levels have not been reported.
 
Hospital wastewaters are a source of bacteria with acquired resistance against antibiotics with a least a factor of 2-10 higher than domestic wastewater. Bacteria become resistant to a specific antibiotic by transfer of genes encoding for this resistance being transferred vertically to the bacteria's offspring or horizontally, among bacteria of different taxonomic affiliation. Gene transfer is optimal at high cell densities and under high antibiotic concentrations. However under heterogenous environmental conditions, this gene transfer can still occur at significant levels. The emergence and spread of methicillin-resistant Staphylococcus aureus (MRSA) is of particular concern.
 
Removal efficiencies of different wastewater treatment techniques for various hospital related pollutants were reviewed from the literature. There was 50-99% removal of antibiotics by powdered activated carbon/granular activated carbon (PAC/GAC), greater than 95% by ozonation, 50-80% using ultraviolet photolysis and greater than 90% using reverse osmosis. Antibiotic resistant propagules (viable bacteria) were reported to be removed by less than 1, 2 and greater than 3 log units by activated sludge in various studies. Therapeutic drugs had a 90-99% removal by PAC/GAC, poor to greater than 95% removal using ozonation and 50% to greater than 90% removal with reverse osmosis. Iodinated contrast media removal by activated sludge varied from none to 85% and by ozonation from poor (14%) to greater than 80%. Oestrogens were removed greater than 99.8% with PAC/GAC and 95-99% using reverse osmosis.
 
There are four possible scenarios for hospital wastewater treatment and disposal: (1) direct discharge to the environment, (2) co-treatment in a municipal WWTP, (3) on-site wastewater treatment and subsequent discharge of the effluent to the environment and (4) first on-site and subsequently municipal wastewater treatment. A risk assessment for the hazard posed by the hospital wastewater needs to be conducted for all 4 scenarios. Scenario 3 could possibly provide the highest efficiency and environmental benefits.
 
Membrane bioreactors (MBRs) have been proposed as a potential alternative for conventional activated sludge treatment. MBR may play a key role in hospital wastewater treatment because of the high removal of bacteria. There are several post-treatment technologies such as activated carbon, ozonation and UV photolysis which remove hospital related pollutants quite well. Reverse osmosis is practically not possible and advisable because of the required pre-treatment of WWTP effluent before using this technique and because of the generation of concentrated sidestreams. Ozonation is relatively cheap but by products are poorly characterised. A proposal had been suggested for source separation of urine of patients which have undergone X-ray imaging. The urine containing ICMs could be processed as chemical waste. This source separation could also be applied to the urine of pregnant women in hospital maternity departments. This urine could be treated in a small scale WWTP which has been enriched with oestrogen degrading organisms. The economic and social feasibility of this needs to be demonstrated.
 
There is a lack of data about the possible impacts of hospital discharges, direct or indirect on the environment. There is a need to develop treatment scenarios for hospital wastewater with regard to attainable efficiency and costs per m 3 of water treated. The idea of uncoupling hospitals from public sewers requires thorough investigation by technologists, ecotoxicologists and public health specialists.
Source :  http://www.waterquality.crc.org.au/hsarch/HS46_b10.htm

CATEGORIES OF BIO MEDICAL WASTE (BMW)
https://www.dpcc.delhigovt.nic.in/bio-medical-waste.html

(Please refer Schedule I , Click here to see the Schedule I)
Category No. 1      Human Anatomical Waste
Category No. 2      Animal Waste
Category No. 3      Microbiology & Biotechnology Waste
Category No. 4      Waste sharps
Category No. 5      Discarded Medicines and Cytotoxic drugs
Category No. 6      Soiled Waste
Category No. 7      Solid Waste
Category No. 8      Liquid Waste
Category No. 9       Incineration Ash
Category No. 10    Chemical Waste
reatment Of Bio Medical Waste 

Category No.1    Incineration /deep burial

Category No.2    Incineration /deep burial

Category No.3    Autoclaving/microwaving/incineration

Category No.4    Disinfection(chemical treatment)/autoclaving/microwaving and 
                            mutilation/shredding.

Category No.5    Incineration/destruction/ and drugs disposal in secured landfills

Category No. 6    Incineration/autoclaving/microwaving

Category No.7    Disinfection by chemical treatment/autoclaving/ microwaving and 
                           mutilation/ shredding

Category No.8    Disinfection by chemical treatment & discharge into drains

Category No.9    Disposal in municipal land fill

Category No.10    Chemical treatment and discharge into drains for liquids and secured 
                              landfill for solids. 
Standards for Liquid Waste



PARAMETERS
PERMISSIBLE LIMITS
pH
6.5-9.0
Suspended Solids
100 mg/L
Oil & Grease
10 mg/L
BOD
30 mg/L
COD
250 mg/L
Bio-assay Test
90% survival of fish after 96 hours in 100% effluent

These limits are applicable to those hospitals which are either connected with sewers without terminal Sewage Treatment Plant or not connected to public sewers. 

For discharge into public sewers with terminal facilities , the General Standards as notified under the Environment (Protection ) Act, 1986, shall be applicable . 
Click here to see the General Standards(Schedule VI) 

Main parameters are given below:




PARAMETERS
PERMISSIBLE LIMITS
pH
5.5-9.0
Suspended Solids
600 mg/L
Oil & Grease
10 mg/L
BOD
350mg/L
Bio-assay Test
90% survival of fish after 96 hours in 100% effluent

DPCC has taken decision that Hospital having 50 beds or more shall install Effluent Treatment Plant (ETP) for the treatment of waste water generated and for recycling of treated effluent for use in horticulture, air conditioning/ cooling plants and flushing of toilet etc. 
In hospitals that have ETP facility, the treatment is carried out using special scientific process and generally involves three stages, primary, secondary, and tertiary levels of treatment. [14]

 Average water consumption 750 liter / bed / day.(International norms) Please calculate daily water consumption from borewell to over head tank using water meter. 80% of total water in nover head tanks is wasted as waste water. This should be the capacity of the STP to be installed at the hospital. (See table below)
Capacity of overhead tank from where water is distributed = A Liter
Number of times Over Head Tanks Filled up in a day = B Nos
Total water requirement for use at different points = A x B Liter/day
Quantity of Effluent , liter per day = 80 % of ( A x B )
Sourcess of waste water
1. Bed in Hospital= Nos @ 500 liter per bed (DPCC norms) = Liter
2. Employee in Hospital = nos @ 40 liter per employee= Liter
3. Hostels- Persons = nos @ 150 liters per person. = Liter
4. Kitchen Meals= nos@ 10 liter per meal = Liter
So, Total Quantity of discharge: --------- liter per day

Health Stream Literature Summary - Issue 46 - June 2007
The treatment of hospital waste water: an appraisal
Pauwels, B. and Verstraete, W. (2006) Journal of Water & Health, (4) 405-416.
PRE TREATMENT
Chemical treatment usually involves the use of 1% sodium hypochlorite solution with a minimum contact period of 30 min or other standard disinfectants like 6% hydrogen peroxide

Primary treatment

Consists of temporarily holding the sewage in a basin where the settled and floating materials are removed and the remaining liquid subjected to secondary treatment. Primary treatment usually removes from 30 to 40% of the BOD. After this treatment the BOD and COD levels usually comes down to 25% of its initial levels.

Secondary treatment

Removes the dissolved and suspended biological matter and is typically performed by indigenous, water borne microorganisms in a managed habitat. This treatment uses microbial degradation, aerobic or anaerobic, to reduce the concentration of the organic compounds. The combined use of primary and secondary treatment reduces approximately 80 to 90% of the BOD. In this stage, there is settling down of the suspended solid contents of the biological waste as thick slurry called sludge, while the treated fluid undergoes tertiary treatment. Through this process, 95% of the pollutants from the waste water are removed.

Tertiary treatment

Uses chemicals to remove inorganic compounds and pathogens. This is the final stage of treatment where the effluent after secondary treatment first is mixed with sodium hypochlorite and then the effluent is passed through dual media filter (DMF) and activated carbon filter (ACF) where sand, anthracite, and activated carbon are used as filtration media. Finally, the treated water is let into a small well to recharge the water table. This treated waste water now can be used for gardening, toilets, and laundry purposes. [15]


WASTE WATER FLOW RATES IN DIFFERENT UNITS:
Waste water consist primarily of used water, the water that reaches the sewer . For different units it is different as shown in the chart .
Source Unit Range l/u/d Typical l/u/d
Apartment Person 200-340 260
Hotel resident Resident 150-220 190
Hotel Employee Employee 30-50 40
Individual Home Person 190-350 280
Airport Passenger 8-15 10
Automobile service station Vehicle served 150-200 200
Restaurant Meal 8-15 10
Office Employee 30-65 55
Laundry Machine 1800-2600 2200
Laundry Wash 180-200 190
Hospital medical Bed
Employee
500-950
20-60
650
40
School Student 20-65 40
School boarding Student 200-400 280
For Industries 80% of water used used in production will be released as waste water
Meat processing Mg 15-20 cu mtr/ Mg
Milk Products Mg 10-20 cu mtr/Mg
Bread Mg 2-4 cu mt/Mg
Beer Mg 10-16 cu mtr/Mg
Whisky Mg 60-80 cu mtr/Mg
Paper Pulp Mg 250-800 cu mt/ Mg
Paper Mg 120-160 cu mtr/Mg
Textile Bleaching (Cotton) Mg 200-300 cu mtr/Mg
Textile Dyeing (Cotton) Mg 30-60 cu mtr/Mg
REF : WASTE WATER ENGINEERING : TREATMENT , DISPOSAL AND REUSE--- METCALF & EDDY .




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